Water containing hydrogen sulfide gas (“H2S”) has a distinctive “rotten egg” odor, which may be especially noticeable when running hot water.
Such water can discolor coffee, tea, and other beverages and alter the appearance and taste of cooked foods. Hydrogen sulfide (“H2S”) gas is a nuisance that is not usually a health risk at concentrations typically found in household water.
Hydrogen sulfide can be toxic. Usually, the gas can be detected long before it reaches harmful concentrations. H2S is flammable and poisonous. While such concentrations are not typical, if gases are released in a confined area, they could cause nausea, illness, and in extreme cases, death.
H2S dissolved in water can corrode plumbing metals, such as iron, steel, copper, and brass, and exposed metal parts in washing machines and other water-using appliances.
The corrosion of iron and steel from hydrogen sulfide forms ferrous sulfide or “black water,” which can darken silverware and discolor copper and brass utensils. Hydrogen sulfide can also interfere with the effectiveness of water softeners and filter systems.
Sources of Hydrogen Sulfide
Iron bacteria and sulfur bacteria present in groundwater use iron and sulfur as an energy source and chemically change sulfates to produce H2S gas. These bacteria use the sulfur available from decaying plants, rocks, or soil and often thrive in an iron-rich environment.
The harmless, non-toxic bacteria usually exist in oxygen-deficient environments, such as deep wells and plumbing systems. The bacteria do not usually cause health problems but contribute to bad tastes and odors at low levels.
The First Step is To Check For Odors in Cold & Hot Water
Run a hose bib or tap as close to the well as possible and fill a 5- gallon bucket or other container and notice if there are odors. If you smell a “rotten-egg” odor, this is hydrogen sulfide gas.
If the water smells like oil or asphalt, this can be from manganese. Also, if the water smells like cucumber or sewage, this is usually a result of iron and sulfur bacteria.
Run the water hot water from each tap and notice an odor in hot water, not in the cold water. This indicates a problem with the water heater. Iron and sulfur bacteria can interact with the anode rod in water heaters, resulting in hydrogen sulfide gas only in hot water.
Changing the anode rod to an aluminum-zinc rod can often solve this problem.
It is recommended that you drain your water heater at least once per year. This will flush out the sediment that may accumulate in the bottom and give you an idea of the sediment type and color, if any, are present.
To learn more about odors and what may be causing them, visit our Odors page or read our guide on “How To Treat Sulfur Odors In Well Water.”
Sulfur odor in pipes after installing a new treatment system?
If possible, we recommend adding a cup of bleach into the pipes after the new softener or whole house filter and flush the water heater and household cold water pipes with some bleach to eliminate the odor.
One thing that can happen with odors is that odors can still develop in the pipes because of bio-films while there is no odor leaving the new treatment system. This can be worse in sections of the plumbing that are not used much.
Introducing a small amount of chlorine (laundry bleach is fine) and letting the water sit for a couple of hours helps sanitize the pipes and prevents the odors from developing in the pipes if that was a problem.
Water Heater Odor Only?
If the odor is primarily in hot water, the water heater needs to be sanitized. Turn off water pressure to the water heater and Add 1 cup of chlorine bleach to the water heater and turn the water back on.
If you have a prefilter housing, you can add the bleach there. If not, remove the inlet flex pipe and drain some water out of the water heater. Run hot water in the home for a minute to get chlorine bleach mixed into hot water and then turn off the water. Let the water heater sit for 2 hours and then run the hot water until clear. Note this may have to be repeated for severely fouled water heaters.
If the odor returns to the water heater, you may need to remove or replace the anode rod.
Sulfur Odors on Your Second Level or Upstairs Floors Only?
In some cases, it is worse on upper floor levels because the gas can rise and appear out of fixtures on the upper floors.
The first step in eliminating this is to ‘shock chlorinate’ the pipes. This is done by adding enough bleach to reach a 100 to 200 ppm chlorine residual and then allowing the chlorinated water to sit in the pipes for 6 to 8 hours or overnight.
If the odor or gasses go away but come back in a few weeks, the shock chlorination process is repeated.
There are various ways to introduce chlorine bleach into pipes, but having a filter housing inline can make it easy.
With a spindown filter, you can easily turn off the water to house, unscrew the filter and add chlorine bleach or peroxide.
Turn the water back on and flush your pipes until you smell bleach or see bubbles from the peroxide.
Let it sit in pipes for several hours.
Turn the water back on and flush the pipes.
No more odors!
Why Does My Water Smell Like Sewage?
If your cold well water smells like sewage, it can be the result of several causes:
Hydrogen sulfide from iron, sulfur or other types of bacteria naturally occurring in your well water
Contaminated pipes with layers of bio-film caused by various types of iron, sulfur, or other types of bacteria.
Septic tank contamination
First, test your water for coliform bacteria using a lab kit or a do-it-yourself-at-home bacteria test kit.
Shock chlorinate and sanitize your well and piping, and retest if the coliform test was positive.
If you still have questions, don’t hesitate to e-mail us at email@example.com, leave us a message on Facebook, or use our online contact form for prompt, personalized assistance from our trained professionals.
Over the last 30 years, we have worked on thousands of well water treatment installations or Well Water Treatment Systems.
Unfortunately, by the time many of our customers work with us, they are installing their 2nd or 3rd well water treatment system after having problems with the water filtration system that they had before.
We realized after some time that there are five common mistakes a lot of homeowners make when choosing well water treatment.
You can easily avoid these problems with a little help and very little time and effort.
The Top 5 Mistakes Include:
1. Failing to analyze the well water chemistry correctly
2. Not having a fundamental understanding of how the well water system works
3. Not knowing the well pump and well flow rate in gallons or liters per minute
4. Not checking the water pressure or having a broken pressure gauge
5. Choosing the wrong water treatment system for the water problem
Water Taken For Granted
Many of us grew up in an urban area with safe-treated city water and later relocated to the countryside. We may never have considered the origin or quality of water. Water was taken for granted to be abundant and safe.
After purchasing a home in the country on a private well, many of our customers have encountered unpalatable or dangerous water for the first time. The well water might be rusty, full of sediment, possess a bad odor, bad smell, or perhaps include harmful bacteria that induce sickness.
Fortunately, there are many different water treatment systems in the marketplace to fix these issues. Unfortunately, quite a few water treatment vendors, retail outlets, or big box stores often have only a few systems supposed to match all situations, yielding poor results and frequent repairs and maintenance.
One size fits all, and “set it and forget it” is all too common in sales claims. Finding the best well water filtration system depends on a good understanding of your well water.
1. Water Chemistry is Vital in Choosing the Best Well Water Treatment System for The Job
Almost all water treatment systems have certain ranges or conditions in which they perform. One example is well waters that are naturally acidic, and at the same time, have iron present. A lot of iron filtration systems cannot take away iron if the water is acidic, and so to begin, the water has to be treated to counteract the acidity in the water.
Knowing which parameters to analyze is important. When the well is located near gasoline stations, industrial sites, or close to an agricultural area where many chemical substances are being used, the water should be analyzed annually for various chemical contaminants to make sure the water remains safe secure.
Suppose septic tanks or livestock in the region, such as cattle or horses, a bacteria test is recommended. For many aesthetic water quality problems, including bad tastes, odors, or perhaps staining, general mineral testing is usually recommended.
This may include iron, manganese, total dissolved solids, pH, calcium hardness, alkalinity, and turbidity. Extra analysis can consist of arsenic, nitrate, sulfate, chloride, sodium, and metals such as lead.
A good water analysis before choosing a system is vital. Without first knowing exactly what is present in the water choosing a tailored approach is not advised.
2. Understanding How Well Water Pumping Systems Work
Most wells pump water from the earth automatically by using a submersible pump. If the well is shallow, they may use a jet pump located on top of the ground level and draws water from the well to create water pressure for the household.
Some well water treatment systems have a large holding tank to hold the actual water before being pumped again to the household. Many other well water filtration systems are gravity fed and employ gravity to produce water pressure for the dwelling.
Understanding the basics of how the well water system performs is essential when selecting a water treatment system. The treatment method’s style could adversely affect the water pressure and the flow rate within the home.
For example, when the well uses a pressure tank, a treatment system must be set up after the pressure tank, not before, to avoid causing damage to the well pump.
3. How Well Pump Flow Rate Affects Water Treatment Systems
Water wells and well pumps come in different sizes and pump water at different rates. It’s easy to test a well pump to determine the actual flow rate delivered from the pump.
Knowing the flow rate will allow the appropriate size water treatment system to be paired with its preferred flow rate. Nearly all well water filtration systems are self-cleaning and need to have a specific minimum flow rate.
The common problem is to use a water treatment system that will require ten gals. Per minute, but the existing well pump can only produce 7 gallons a minute. After several weeks, the water treatment system fails to backwash properly and becomes fouled.
The water filter media can seize and solidify, rendering the entire water system impossible to use. Sizing a plan so that the flow rates are met is infinitely important to ensure enough force to move the well water through the media bed to lift the media and allow full cleaning.
Oversized water systems will cause loss of pressure, while an undersized system can see media be pushed into plumbing downstream of the filter.
4. Water Pressure a Major Factor in Choosing Best Well Water Treatment System
Water pressure also has a crucial role in selecting a water treatment system. Virtually all water treatment systems will decrease the water pressure as the water flows through the equipment.
It is important to know the water pressure from the well pump and pressure system before selecting a well water filtration system to end up with decent water pressure inside the bathroom, and other fixtures home appliances.
Many good pump systems are generally fine-tuned to operate better if the pressure is not high enough, to begin with.
5. Deciding on the Best Well Water Treatment System for the Job
While some well water treatment systems get rid of several pollutants, no one treatment system can work for every application or water contaminant.
When choosing the best water filtration system for well water, it is important to know the capability of the water treatment methods that are being considered, what impurities they extract, precisely what several flow rates they will process, and what water pressures they will operate within.
How to Eliminate Odors and Freshen Well Water with Hydrogen Peroxide
Did you know that you can use hydrogen peroxide to kill sulfur odors in your well water? Peroxide works great to eliminate "rotten egg" and other odors in well water. This is the same hydrogen peroxide found at the local pharmacy or supermarket but in a slightly higher concentration.
If your well water smells like rotten eggs, you’re not alone. Well water odor is a common problem. Many homeowners on well water battle the stinky hydrogen sulfide.
Rotten egg hydrogen sulfide-laden water has an objectionable odor, but higher concentrations can be dangerous to health. It’s corrosive to plumbing fixtures and appliances because when hydrogen sulfide is formed and gets into your groundwater, you get sulfuric acid.
That makes the water tarnish fixtures and eat up the pipes. This unique rotten egg odor, hydrogen sulfide, is usually found in hot and cold water and can sometimes be worse in your water heater and hot water.
It can be a problem. It not only fouls and ruins water softeners and filter systems if not properly treated, but it’s corrosive to pipes and fixtures and just generally a nuisance.
Historically, aeration has been a common way to get rid of smelly water. Chlorine, however, has some undesirable byproducts and can leave chlorine taste and odors if not properly set upright.
Also, if the pH of your water is over 7.5 to 8, in other words, if you have alkaline water, then you have to use a lot of chlorine to get it to kill the hydrogen sulfide rotten egg odor. We found, as a lot of other folks do, we found that hydrogen peroxide does a better job.
Aeration can work well, but if you have iron or sulfur bacteria present, sometimes the bacteria can still create odors after your aeration system. In other words, it can develop in your water heater and plumbing system.
Aeration systems can also be more expensive to set up at times compared to peroxide injection. Peroxide, if you have the right concentration, can kill these iron-sulfur laded bacteria.
So the 4 reasons hydrogen peroxide works:
1. It works faster than chlorine, so often, no contact tank is required
2. Unlike chlorine, the peroxide will not leave a chemical residue or chemical by-products after it’s injected into the water.
3. Peroxide works over a wider pH range
4. Does not affect taste; it often improves the taste compared to chlorination
Over the last 10 years or so, hydrogen peroxide has become a preferred method of treatment for odor by many well water contractors and water treatment specialists all across the U.S. and Canada.
Peroxide and Chlorine
So you might ask: Hey if peroxide is so great, would you ever use chlorination? Well, yes, because chlorine has residual. If you have a chlorine residual, it works better to disinfect your water throughout a distribution system or plumbing system.
That’s why it’s used in communities and municipal systems because you want a chlorine residual to kill bacteria in the pipeline.
Chlorine is cheaper, too, as far as home systems go. Chlorine is less expensive; peroxide can be more expensive. Chlorine has a taste, but you can remove the chlorine taste by activated carbon.
But generally, peroxide is kind of like the deluxe way to go. Usually, it’s better than chlorine when you have a smelly odor problem, and you’re trying to eliminate sulfur and iron-related bacteria in time.
If you have smelly water in your house, you can try to take two-quart jars or large glasses and fill them with your untreated well water. Then, add a teaspoon of household bleach in one and add a tablespoon of 3% store-bought hydrogen peroxide in the other one.
Shake them up and let them sit for a few hours, then smell the water.
You can taste it if you want. It wouldn’t kill you. The one with bleach, you might smell chlorine, but anyway, you’ll find that depending on how much sulfur you have in your water, you might have to add more peroxide or more bleach. You’ll find that the one with peroxide smells and tastes much better than the chlorination one.
Hydrogen Peroxide For Well Water: How it's set up?
So for big home systems, peroxide is usually set up so that it’s automatically injected into the water before your pressure tank. Most folks will use a backwashing carbon filter after the pressure tank or at the house to filter out any residual peroxide and remove that odor.
With the carbon systems (there’s more information on this on the site), we use what we call catalytic activating carbon. That works really well with peroxide because a catalytic reaction occurs.
If there is peroxide residual in the water along with the hydrogen sulfide, you get a very high level of oxidation occurring right on the carbon itself. After it flows to their home, the result is really clean, odor-free water.
So that’s a simple system. Well turns on, automatically injects peroxide into the pipe before the pressure tank, goes through the carbon filter, and then you have clean water free of odors.
One thing that comes up a lot is contact tanks. In chlorination, we often use contact tanks, like a pressure tank where the water goes in, and you give it some time for the chlorine or peroxide to come in contact with water.
The reaction takes place in this tank over a few minutes. Say if you have 1 or 10 parts per million of hydrogen sulfide and you are just using hydrogen peroxide, you can use hydrogen peroxide without a contact tank and just run it straight into the carbon filter, and the reaction takes place right at the carbon filter and you have clean water without odor.
However, there are some cases where you might want a contact tank. If you have iron or sulfur-laded bacteria, hydrogen peroxide doesn’t kill bacteria instantly.
You’ll need a few minutes for the peroxide, and you’ll need a little higher dose as well, over more than what the hydrosulfide is, to have any effect on the bacteria. That’s why we do often recommend a contact tank, but it’s optional. Some people use it; some people don't.
So one thing that comes up is: What strength or concentration of hydrogen peroxide should I use?
This hydrogen peroxide comes in many strengths. Store-bought is 3%. That’s generally safe. The type that we use is, and we can ship safely, and still considered relatively safe, is 7%.
Mainly because it’s safe to handle, it’s not hazardous. You can often find 35% commercial peroxide locally, and it is usually cheaper.
Much cheaper, by the way. However, many people still don’t do it because 35% can be very dangerous to work with.
You have to be very careful. If you spill any, it’s a disaster. Don’t get any on the skin. It’d be a disaster to get it in your eyes. You have to be careful with it. But some people do use it.
Especially if you have a commercial application like for your hog or poultry farms, sometimes it's high flow compared to a home, and it’s much more economical to use the 35%.
But 7% works well. But you know, even 3%, of course, you have to be very careful with it. It’s something you want to keep out of the reach of children. You don’t want it soaking on your skin. Anyway, the concentration we recommend is 7%.
I’ll talk a little bit about where the peroxide system is installed. I put some links to the diagrams on the podcast show notes so you can see how it’s set up.
The lowest-cost way, and how most folks do it, is you have a simple metering pump, and it’s wired and set to turn on whenever the well pump turns on.
Your well pump turns on at, say, 30 or 40 psi, and it turns off at 50 or 60 psi. That’s almost how folks have it. They have a single-speed well pump, and when it turns on, you have it set so that the metering pump turns on at the same time. When it turns on, injects a tiny bit of peroxide into the pipe right before the pressure tank.
That way, that water right there is flowing at the same flow rate. So that way, you can easily control the residual that you’re injecting and put in enough peroxide to do the job. You don’t want to put in too much.
So you can easily regulate that and calculate that if you are putting it into a known stream of water. So the injection point is actually an injection check valve.
The metering pump is pumping in the peroxide through the injection check valve. But when the system builds up the pressure and shuts off, no water can come from your pipe into the peroxide pump and solution tank.
So some folks have a variable speed pump or sometimes called a constant pressure pump. These are pretty popular, so if your well pump is that type, you don’t have a traditional large pressure tank but a tiny pressure tank.
Basically, that type of flow system keeps your pressure in your house the same all the time.
Proportional Feed Hydrogen Peroxide System
For that, you need a proportional feed hydrogen peroxide system which is also very simple, and in some ways, it’s easier to set up than the other type, which is the standard one that is cheaper. With the single speed, you have to do a little bit of wiring and wire it in the pressure switch, which should be the same voltage.
Most folks have a submersible pump, 220 volts. You get the metering pump, and you have it wired into your pressure switch. It's pretty easy to do. You can also have an electrician do it if you don’t know how to do it.
However, that won’t work with a variable speed pump or a constant pressure type of system.
So what do you do? Well, it is very simple, you set up a proportional feed system. All it is is a water meter that you install in the pipe.
In this case, you could put it in the house. You don't have to have it at the well. Basically, what it is, it’s a flow meter.
When water flows through this water meter, it sends out a pulse and turns on your peroxide pump to pump more or less, depending on how fast the water is flowing.
So if somebody is brushing their teeth, that might be a gallon a minute, and someone is taking a shower, might be 5-gallons, and all of a sudden the washing machine is coming on, and all that will affect the flow rate. Whatever the flow rate is, you’ll still have the exact amount of peroxide all the time.
In some ways, those systems are a little safer to use because, although pretty rare, of course, it does happen. You can have a situation where your well pump dies.
So say your well pump is off, but you’re still getting voltage to it, and the peroxide system doesn’t know it, so the peroxide pump is just stuck on and pumps the entire solution tank right into the pipe.
If nobody knows and they turn the well pump back on by accident and start to use the water, you get many peroxides. It’s not likely to happen, but there you go.
So having a proportional feed system can prevent that type of thing and is one more advantage. But those are more expensive, so people are more likely to get the standard one.
Peroxide dissolves the iron.
One question that comes up when discussing hydrogen peroxide for well water is: How about iron removal?
Seems like many folks, a lot of sites, and my local water treatment guys talk about peroxide for iron removal. Well, usually, it does work well for iron too. Peroxide can definitely oxidize the iron.
Iron is often dissolved in the water and may look clear but tastes terrible like rust, and then when it gets exposed to air, or it gets hit with peroxide, it turns to rust.
...but you still need to filter the dissolved iron
So what you can do is use peroxide injection and have that be filtered out by an activated carbon filter or, better yet, an iron filter. That’s usually what we recommend.
If you have high iron levels and use peroxide with carbon, you must have it set pretty carefully.
It has to work just right for it to remove all the iron. And if anything ever happens to peroxide, say you forget to add the peroxide, you can add it, or maybe the peroxide you got is old, then you got iron water running through a carbon filter, and that does not work.
It doesn’t take out much iron. It could flow right through it because you got dissolved iron in the water.
What you need to filter the dissolved iron in your water
In our experience, it’s better to use what we have. We have Pro-OX, a manganese dioxide filter media, but there’s also Filox, Pyrolox, and other different available brands that work well.
We usually do recommend a contact tank with that. Basically, what you’re doing is you’re injecting the peroxide, you’ve got your contact tank where a lot of oxygen is being put in the water, and then the Pro-OX or the manganese dioxide works really well.
Then if something ever happens to the peroxide, the Pro-OX will still work. It just works better with some oxidation like peroxide, or chlorination but it’ll still work on its own, so it’ll give you a break if something ever happens to your system.
However, there are a lot of people that do use peroxide with carbon. It does work, so that’s another way to go. But we don’t really recommend it. If someone has really high iron and odor, and they want to use peroxide, then we recommend a 2-stage system.
The 2-stage filtration has Pro-Ox, and then the carbon filter. That will last for years, and you will have really great water - no peroxide residual in the water, and it’ll clean out all the odors and sediment and work really well.
Will Peroxide kill coliform bacteria?
Another question that we get a lot is, Hey, what about hydrogen peroxide for e-coli?Or how about coliform?
There’s a lot of controversy about this as some water treatment professionals say hydrogen peroxide works great for coliform.
Generally, though, I put a link to this because there are many references to this. Still, hydrogen peroxide itself is rarely used in drinking water or treatment as a stand-alone process.
The fact that it doesn't last long is kind of an advantage for residential use. There’s not a chemical residual in it. There are advanced oxidation processes where we use hydrogen peroxide with UV light or inject hydrogen peroxide before ozone.
That produces very high levels of hydroxyl radicals which are really effective at killing bacteria. It also does remove pharmaceuticals or other weird organic compounds, but that usually is not necessary for most homes.
So if you know you got coliform and still want to use hydrogen peroxide, then after filtration, you want to have an ultraviolet sterilizer. At least, that’s my opinion.
You don’t want to rely on hydrogen peroxide alone. In fact, generally, if you have e-coli or coliform (I talked about this in another episode), you want to find out what’s the source of it. Don’t just try to treat it. Find out what’s causing it, and then fix that.
If it’s impossible to fix, let’s say your well is next to a river, and it’s always going to be in the influence of surface water, then you need a very careful type of treatment system that will really deal with that.
Okay, we don't recommend hydrogen peroxide as a disinfectant, although we say it is effective for iron and sulfur-producing bacteria. If health is a factor, like with coliform, we recommend chlorine.
Test to see if the peroxide works
Another thing that comes up a lot is: How can I adjust the peroxide? How do I know it’s working?
These pumps come in different sizes that inject the peroxide, and it depends on how many gallons per minute you’re trying to treat. Here’s the basic overview: What you want to do is you want to inject enough peroxide to overcome the hydrosulfide and interact with any organic bacteria.
When it does that, it’s gone because the peroxide gets used up. So you want to keep injecting enough, so you have a tiny residual, either after the contact tank or, in some cases, right after the carbon filter. You’d be looking at somewhere between .2 and .8 parts per million peroxide.
You don’t want a high level of peroxide in your drinking water. So afterward, you have a very tiny amount, that's good, or you have none, that’s the best.
If you have a contact tank and a hose bib between your contact tank and your carbon filter, you want enough residual before it goes to your carbon filter, say between 1 and 2 parts per million.
If you don’t have a contact tank, you want enough residual to do the job, but you have very low residual or no residual afterward. Now that sounds kind of too general. There are ways you can actually figure it out with simple test kits.
For example, if you test your water and you estimate you have 5 or 8 parts per million of hydrosulfide and say 1 per million of iron, then you can look at a table and figure out how much hydrogen peroxide to add.
Now I know I need 8 or 10 parts per million of hydrogen peroxide to do the job.
And that’s kind of what you’re looking at. Usually, you inject somewhere between 2 and 10, maybe 15 if you have a high odor level, parts per million of hydrogen peroxide. You can then get a peroxide test strip or test kit, test it in your house or after your treatment system, and make sure you don’t get a high residual because you don’t want to drink water with hydrogen peroxide.
Alright, that about covers it. In this episode, we talked about how great peroxide is for well water odor, how to set up a basic system, when to use the contact tank, and how to test for the peroxide to make sure it’s working.
Thank you for listening, and I hope to talk to you on the next podcast. Hey, if you’re listening to this on iTunes, I really appreciate a rating and an honest review over iTunes.
That helps a lot, and I really like your emails and questions regarding the podcast, so please send an email if you have any questions or comments. firstname.lastname@example.org
If you want to listen to my podcast episode on peroxide, go to our site cleanwaterstore.com/blog/podcast Thanks to the along with the great links and resources. Have a good day.
Chlorine is an effective and low-cost chemical for disinfecting water storage tanks. We are often asked:
How much chlorine is needed to treat water?
How much chlorine bleach do I put in my water tank?
Using the charts below you can find out how much Chlorine Bleach is needed to disinfect and purify specific quantities of water, for example, 1,000 gallons. On this page we will talk more about the chlorine to water ratio and how much chlorine to put in drinking water.
If your tank is new, has been worked on recently, or you know it is contaminated, perform a “shock chlorination” with 50 to 100 parts per million (PPM) and let sit for 12 to 24 hours.
After you add the chlorine, the chlorine levels will start to drop. Chlorine is used up and breaks down depending on the chlorine demand (your water’s chemistry and conditions) and the temperature of the water.
Test the chlorine residual after 24 hours and if the chlorine levels are 10 PPM or less, repeat the procedure. If you are storing water and want to keep a chlorine residual to be safe, use maintenance residual of 1 – 2 PPM.
Two Methods: Shock Chlorination Or Chlorine Maintenance Residuals
Shock chlorination adds chlorine until the residual reaches 50 to 100 PPM. This is recommended when you have a new storage tank or have work done on the well, or you find out the storage tank is contaminated with coliform bacteria.
Shock chlorination will make the water unusable for potable use until the chlorine levels drop below 2–4 PPM, which typically occurs within a few days to a few weeks depending on temperature and water chemistry.
Maintenance or Low-Level Chlorination
Don’t want to use shock chlorination? It is best to use an automatic chlorinator if you wish to automatically maintain a chlorine residual to keep your storage tank disinfected as freshwater flows into it.
However, if your storage tank is for long-term storage or you wish to periodically chlorinate see the chart for adding 1 – 2 PPM.
A chlorine residual of 1 to 2 PPM is recommended if you plan to maintain a chlorine residual for potable water use. Follow these steps and see the chart below to find out how much chlorine bleach to add to achieve these residuals.
Step 1: Clean The Storage Tank First
Clean the storage tank or reservoir. Remove debris and scrub or hose off any dirt or other deposits or interior surfaces. Pump to remove any suspended solids or foreign matter in the water if possible.
Step 2: Use Strong Chlorine Solution
If possible, scrub interior surfaces of storage or reservoir if applicable with a strong chlorine solution containing ½ gallon household bleach, or ¼ gallon of pool chlorine to every 5 gallons of water.
Make sure there is adequate ventilation. Enclosed spaces are dangerous and can cause illness or death.
Step 3: Inspect For Damages
Inspect the storage tank for cracks, leaks around the lid or man-way, or vents. Make sure no insects, rodents, or other debris can enter the tank during normal operation of the tank and water system, by making sure the lid is tight-fitting, and any vents are properly screened.
Use the chart below to decide how much chlorine bleach to put in the water tank, to bring up the chlorine residual in the tank to the desired level.
For example, you can use the chart below to find out how much bleach to disinfect 1,000 gallons of water and what chlorine to water ratio is needed to treat water.
NOTE: If you need to use the water in the tank immediately after chlorination, consider adding enough chlorine to bring the levels up to 5 or 10 ppm and let sit for 12 hours or more. Use 50 to 100 PPM chart only if you are doing shock chlorination for new or heavily contaminated storage tanks.
Storage tanks: Disinfecting with liquid household bleach (5.25% Sodium Hypochlorite)
Step 4: Use Bleach
If using pool chlorine (12% sodium hypochlorite) use half the amounts below.
Storage Tank Gallons
Approx. parts per million of chlorine residual achieved by adding 5% chlorine bleach, in the amounts below.
1.0 qt. (32 oz)
1.5 oz (3 tb)
19 oz (2-1/2 cups)
2.5 oz. (5 tb)
12.8 oz. (1-1/2 cups)
1.25 oz (2.5 tb)
6.4 oz (3/4 cup)
3 – 4 teaspoons
3 oz (6 tb)
1.3 oz (2.6 tb)
1 pint or 2 cups
Step 5: Drain and flush tank
Drain and flush tank if using these higher levels of chlorine. Don’t put water with chlorine residual into drains leading to septic tanks, and avoid discharge into creeks, rivers, or lakes.
Be careful if you have a steel storage tank, as corrosion may have occurred over time, and once the tank is cleaned it may develop leaks.
A general rule of thumb to shock chlorinate and disinfect a storage tank is to mix non-scented NSF-approved household bleach (5.25% chlorine) in the reservoir at the ratio of 1 gallon of bleach for every 1,000 gallons of water (i.e., 1 quart for every 250 gallons of water).
This will give a chlorine concentration of 50 ppm, far higher than the 0.5 to 2.0 PPM found in treated city water, and make the water unusable for potable water use until residual drops down to less than 4.0 PPM.
For storage tanks or cisterns fed by well water: Add bleach directly to the storage tank at the same time, you are disinfecting the well. Let the storage tank drain into the distribution system.
After sitting for 12 to 24 hours, drain the storage tank through a drain valve or through the distribution system.
Do not dispose of chlorinated water into a septic tank or on vegetation or into surface water.
If you cannot find NSF-certified chlorine bleach use NSF-certified chlorine pellets or powder.
Storage tanks: disinfecting with dry 1 gram chlorine pellets, or chlorine granules. Do not use pool bleach. Use calcium hypochlorite for potable water.
1 cup pellets = 200 pellets = 1/2 lb
2 cups pellets = 400 pellets = 1 lb
25 pellets in 100 gallons = 50ppm
50 pellets in 100 gallons = 100ppm
Storage Tank Gallons
Approx. parts per million of chlorine residual achieved by adding dry chlorine pellets in the amounts below.
1 cup = 8 fluid oz.
1 pint = 16 fluid oz.
1 quart = 32 fluid oz.
1 gallon = 128 fluid oz.
1 teaspoon = 1/6 fluid oz.
3 teaspoons = 1 tablespoon
1 fluid oz. = 29.6 milliliter (ml)
20 drops = 1 ml.
What Type of Chlorine Is Best to Use?
Besides knowing how much chlorine to put in water storage tank, you also need to decide on which type of chlorine to use.
There are three main types of bleach available to use to sanitize your water storage tank.
The worst option is to use household laundry bleach, Clorox. This contains unwanted chemicals besides chlorine. Laundry bleach does work and will disinfect your storage tank, so that is an option. Make sure to use non-scented.
The best chlorine bleach that is certified for drinking water. If you cannot find liquid bleach that is NSF certified you can use dry NSF pellets or powdered bleach.
A second good option is to use liquid pool chlorine, which is sodium hypochlorite without additives (unlike laundry bleach). You can usually find liquid pool chlorine at Home Depot or Lowe’s or hardware stores and also spa and pool supply companies. Pool chlorine is liquid 10-12% sodium hypochlorite, which means it has 10 to 12% chlorine.
An easy-to-use NSF-certified chlorine bleach is chlorine granules with no additives. This type is calcium hypochlorite and can be mixed with warm water and put into storage tank.
Do not use dry powdered pool chlorine, sometimes known as Tri-Chlor in your storage tank or well water.
Which Chlorine Test Kit Should I Use?
After you figure out how much chlorine to put in water storage tank, you may want to have a chlorine test kit on hand to know the chlorine residual after you have chlorinated your storage tank.
Having test kits offer two main benefits:
You can tell if you have added sufficient chlorine to your tank because you can measure the chlorine levels.
You can know when the chlorine has dropped to safe levels (less than 4.0 PPM) if you need to use the water in the home.
A common low-range chlorine test kit uses Orthotolidine which turns yellow if chlorine is present so it is easy to use.
Test strips are easier to use but for low range, the reagent type may work better in our experience.
You also may want a High Range Kit if you are “shock chlorinating” the tank with high levels of chlorine over 5 PPM.
A low range kit allows you to check for chlorine levels if you are adding chlorine to maintain a low level residual, or you want to know when it is safe to use the water.
Is Chlorine Dangerous or Bad for My Health?
According to the CDC and World Health Organization and health authorities, chlorine levels up to 4 milligrams per liter (mg/L or 4 parts per million (ppm)) are considered safe in drinking water. At this level, harmful health effects are unlikely to occur.
There are studies that show that showering and drinking chlorinated water over your lifetime may increase your chance of getting some cancers, however adding chlorine to kill bacteria in your storage tank and then draining the water out will not have any health effects.
In municipal treatment plants, chlorination is the process of adding chlorine to drinking water to kill parasites, bacteria, and viruses. Different processes can be used to achieve safe levels of chlorine in drinking water. Using or drinking water with small amounts of chlorine does not cause harmful health effects and provides protection against waterborne disease outbreaks.
Water comes from a variety of sources, such as lakes and wells, which can be contaminated with germs that may make people sick. Germs can also contaminate water as it travels through miles of piping to get to a community. To prevent contamination with germs, water companies add chlorine to keep water safe.
Liquid bleach and chlorine powders and pellets can be hazardous to work with unless you use some common sense precautions. Use gloves and eye protection and avoid breathing chlorine fumes or exposing your skin to chlorine.
What about Hydrogen Peroxide? Can I Use Peroxide Instead of Chlorine?
You might wonder if peroxide can be used instead of chlorine to sanitize your storage tank but this won’t work.
You can use hydrogen peroxide on cuts or abrasions to kill germs but it is not a good disinfectant for drinking water. Hydrogen peroxide is rarely used in drinking water as a stand-alone treatment process. It’s a very weak biocide compared to chlorine or ozone.
It’s not approved by the EPA and other health authorities as a stand-alone disinfection treatment process. Hydrogen peroxide is great for removing odors and making water taste better but it is not useful for the disinfection of storage tanks.