Wednesday, June 24, 2015

Low pH and Iron in Irrigation Water

I have a well for irrigation only that has as far as I can tell, iron bacteria.  The water overspray stains the driveway, house, etc.  I also get a sulfur odor at times.  The pump is connected directly to the irrigation system (no pressure tank).  It is a 4" well with submersible pump.  I have tried shock chlorination several times to no avail.  I probably use 1800 gal/day, 3 days/week during the warm season – say 8 months out of the year. The pipe size at the well is 1.25”, although all of the sprinkler piping is 1”.  The line pressure at the well is 55 psig @ 12 gpm flowrate.
I don’t care about the odor – just wanted to mention it since that is indicative of the source of the water quality problem. 

The pH is low at between 5 and 6.  Will this present a problem for this filter?

The filter does not need any chemicals to regenerate, just needs to be backflushed? Presumably I would need to install a pressure tank with pressure switch on the well so that the unit could backflush when called for?  Currently, the well pump just comes on when the irrigation controller commands (pump start relay)

Why two units?  The flowrate seems to be within the parameters of one of the units.  Is it for capacity / saturation of the media prior to backwash cycle?

Last year, the individual at cleanwaterstore recommended chlorine injection with contact tank and Greensand iron filter.  I’m sure there are several ways to attack the problem – just wanted to mention the system that was proposed last year.  I’m not angling for this solution, just wanted to mention it.

Simpler and cheaper is always better.

Let me know your thoughts



Hi Adam,

Actually yes, the very low pH will sort of complicate things.  Any oxidizing iron filter like the Pro-OX system has a specific pH range in which it will work.  The Pro-OX can usually work pretty well with a pH of as low as about 6.3 to 6.5 or so, but if you’re between 5 and 6, that’s problematic.  We would suggest treating the water with soda ash injection to raise the pH up to neutral for best results.  You could always try iron filtration first without addressing the pH, but it’s hard to guarantee that it will work.

The Pro-OX system doesn’t require any chemicals to regenerate, that’s one of its main advantages over other systems like a greensand filter system.  It just relies on water flow and pressure to clean it out.

You could either install a pressure tank and pressure switch, or, you could purchase a small add-on to the unit called an auxiliary microswitch.  The microswitch sends an electrical signal out during the backwash cycle, so you set it up to trigger the pump on.  Overall it’s a little easier to just set up a pressure tank and pressure switch, but it’s also more expensive to do so.

As for the question of why two units over just one unit- that’s because there’s a difference between average flow rate and what is called “service” flow rate.  When used intermittently to supply household usage, the systems can treat relatively high average flows.  That’s because in those cases, treated water is given time to sit in the tank allowing it to have a lot of contact time with the media and effectively remove all the iron, so if a customer runs a shower for ten or fifteen minutes, it’s fine to use a somewhat high flow rate.  But for continuous flow, or “service” flow rates where the water runs non-stop for many many minutes at a time, each individual 2.5 CF system can only treat water up to about 7 gpm or so, so the combination of the two in parallel would be necessary in order to match your high flow rate.  In other words, our published flow rate information on our website is only applicable to residential usage to supply households using intermittent flow.  As a rule of thumb, for irrigation service flow, it’s whatever the published flow rate is divided in half.  I hope this all makes sense; the whole concept of service flow rates is a little confusing to explain so please email or call back for clarification about this.  Sometimes it’s easier to talk it over on the phone.

Pro-OX 7000-SXT
Pro-OX 7000-SXT, 2.5 CF Size (two plumbed in parallel)

Pro-OX™ contains 80% manganese dioxide in an extremely unique cluster format for enhanced performance and maximized capacity.  
Uses the Enpress tank with Vortech distributor which allows the Pro-OX media to be backwashed at lower flow rates with less water, saving water and energy.

Dimensions: 13" diameter x 57" height   ¾" or 1” pipe size.  Bypass is included.

Click here for more information about this product.