A water well sand filter is bought to stop grit reaching the house, and it does that. What it cannot do is stop the well producing sand in the first place, and a well that pumps sand is wearing out its own pump, filling its pressure tank and telling you something about the screen or the pump setting.
Two different things get called a sand filter
One is a backwashing media tank, where water passes down through graded sand or a manufactured media bed and the trapped material is flushed to drain periodically. The other is a spin-down separator or centrifugal sand trap, a clear-bodied device that spins heavy particles out and drops them into a flush valve you open every so often. On residential wells the spin-down is usually what people want, because it handles coarse sand without cartridges and takes seconds to purge.
Why the well is producing sand at all
Sand in the water normally means the pump is drawing from too close to the bottom of the borehole, that the screen or the gravel pack has failed, or that a screened well has been over-pumped and is drawing formation material. Raising the pump, reducing draw, or repairing the screen addresses the cause. That work is a well contractor's job rather than a treatment purchase, and if you skip it the sand keeps grinding pump impellers and check valves whether or not a filter protects the house.
Where the equipment belongs and how it is sized
Put a separator between the pump and the pressure tank when the aim is protecting the tank and the switch, or after the tank when the aim is protecting only the house plumbing. Size it on flow rate, since a separator below its rated flow does not spin hard enough to work and above it simply passes sand. Follow it with a cartridge sediment filter for the fine material that a separator cannot catch. Our well water filtration system guide sets out the order when other treatment follows.
What a sand filter will not do for you
It is a mechanical device and it does nothing about dissolved iron, hardness, sulfur odor, nitrates or bacteria, all of which pass straight through. If your water is cloudy rather than gritty, the cause is fine clay turbidity or oxidized iron and a sand trap will not clear it. Diagnose the particle before buying: catch some in a clean jar, let it settle, and see whether you have sharp mineral grit, soft rust flakes or a haze that never settles at all.
Questions people ask about water well sand filter
Will a sand filter stop my pump wearing out?
Only if it sits between the pump and the tank, and even then the pump is still passing sand. Fixing the well or the pump depth is the real remedy.
How often do I flush a spin-down separator?
As often as the collected sand shows in the clear bowl, which can be weekly on a bad well and monthly on a mild one. It takes a few seconds.
Does a sand filter remove iron from well water?
No. Dissolved iron passes through and only oxidized rust particles are caught, so iron staining needs a proper oxidizing iron filter.
Sand filter or cartridge filter for well water?
Use both where sand is heavy: the separator takes the coarse load without consumables, and a cartridge behind it catches the fine material.