Sand in well water is a symptom with a cause down the hole, and filtering it is treating the symptom. A well that suddenly produces sand is telling you something has changed: a failing screen, a cracked casing, a pump set too low, or a formation being drawn too hard. Fitting a filter without finding out which is how pumps get destroyed quietly.
The likely causes, in order
A worn or corroded well screen lets formation material through where it used to be excluded. A pump set too close to the bottom draws from the sediment that has collected there. A pump oversized for the well pulls water in fast enough to mobilize fine material from the formation. A cracked or corroded casing admits material from a shallower layer. And a newly drilled or newly serviced well often produces sand for a while until it settles.
Why this is urgent for the pump
Sand is abrasive and a submersible pump is not built to handle it. Impellers and seals wear, efficiency drops, and eventually the pump fails, usually earlier and more expensively than the well work would have cost. Sand also wrecks pressure switches, fouls the pressure tank bladder, cuts out toilet fill valve seats and settles in the water heater. If you are seeing sand, the clock is already running on the pump.
What actually removes it
A centrifugal sand separator ahead of the pressure tank spins heavier particles out and discharges them, handling coarse sand continuously without a cartridge. A spin down screen filter with a flush valve catches grit and can be purged without dismantling anything. Cartridge filters work on the remaining fine material but plug quickly if used as the first line. On a well throwing sand steadily, the separator or spin down goes first and the cartridge polishes.
Get the well looked at
Filtration protects the house downstream of the pressure tank, but the pump usually sits upstream of everything you can fit, so no filter protects it. A well contractor can check pump depth, pull and inspect the screen, camera the casing and check whether the pump is oversized for the well's yield. Do that first, then size treatment for whatever remains, and pair it with a proper test as our well water filtration system guide describes.
Questions people ask about sand in well water
Is sand in well water dangerous to drink?
Sand itself is inert, but a well admitting formation material may also be admitting bacteria or surface water, so a lab test is warranted.
Will a sediment filter stop sand damaging my pump?
No. The pump sits upstream of any filter you can install, so filtration protects the house but not the pump. That needs well work.
Why did my well suddenly start producing sand?
Common triggers are a failing screen, a pump set too deep or too large for the well, a cracked casing, or recent well or pump servicing.