My well has recently started to pump small amounts of sand. It is very annoying and clogs up my fixtures. I am going to get a filter for it, but I am curious as to what causes this? I don't have any problems with water, I think there is a lot of water in the well and don't run out of water.
There are many reasons for sudden occurrence of sand or grit in a water well. It usually is a good idea to seek advice from a well driller or pump contractor to determine the source or cause. If the sand has been occurring for a long time it can be strained or taken out after the well prior to the household piping.
If a well suddenly starts to pump sand, this may signify that the well is filling with sand. Typically the well pump is installed so it's a minimum of twenty feet higher than the bottom of the well. When the pump is all the way down near the base of the well, sand or grit and sediment may be sucked in. In old wells the well shaft might fill with fine sand and sediment so much that the water pump can start to pull in sand from the bottom.
Other sources for sand in water may be the fact that well screen is becoming degraded and is permitting sand as well as sediment in from the area around the well screen. Wells are constructed of shafts called casings, which are usually made of steel, iron, or PVC. The casing is the well shaft that is installed by the well drilling contractor. Your well has openings that allow water to penetrate the well from the surrounding ground water and also at the same time screen out sand and grit. This is called the well screen. Through time the well screen can become deteriorated as well as corroded and allow silt and/or sand to enter the well.
Sometimes the well pump may be too big a pump for the well and draw sand or grit in from the adjoining water table. Sand can be very hard on the well pump and can rapidly wear out the pump, fill the base of the well. But whatever the cause, a rapid occurrence of sand is not a good sign and the cause needs to be established.
In the event you do see a lot of sand in your water it is best to contact your well contractor or driller to discuss the situation and discuss possible ways to correct this condition. Sometimes the well driller can pull the pump up 10 to 20 feet in addition to end the sand problem. For some wells a new casing may be advised. There are also special screens that the well contractor can install over the pump to keep out sand, although these are not feasible for some wells if the casing is very old or the well diameter too small. In the worst case scenario, it is not possible to repair the well and a new well is needed.
If the sand is slight or it has been ongoing for a long time and not gotten worse, one solution is to install a centrifugal sand separator on top after the well. These systems remove sand and sediment by centrifugal force. The water rotates inside the separator and any sand ends up in the bottom of the separator, whereby it can be easily flushed out by opening a small valve at the base of the separator. No filters are used.
An alternative solution to the centrifugal separator is a spin-down filter screen which has a small valve located at the bottom of the filtration system. The screen filters out the sand but may be cleaned by means of opening the ball valve and thereby flushing the filter screen. These types of filters must not be too fine, because they can result in pressure loss. Normally a 60 to 100 mesh size screen is good for straining out all sand and grit. These types of filter screen are installed after the pressure tank.
Both the centrifugal sand separator and the screen filters have manual ball valves that allow you to flush out the sand. If you use a lot of water or have a lot of sand which requires this to be done frequently, an automatic flush valve can be installed. These valves turn on for a few seconds and flush out the accumulated sediment and keep the sand trap clean automatically.