Well pumps · water quality and protection
Sand and sediment in well water: spin-down filters
Sand and grit in well water wear out faucets, valves, pressure switches, and softener control valves. A spin-down (screen) sediment filter catches the heavy particles and lets you flush them out in seconds. But sand can also be a sign of a well or pump problem a filter will only hide.
First, ask why there is sand
| Pattern | Possible cause | What to do |
|---|---|---|
| A little fine sand since the well was drilled | Normal for some aquifers and well designs | A spin-down filter is a sensible fix |
| Sand appears suddenly or increases | Damaged well screen or casing, or a change in the aquifer | Call a licensed well contractor |
| Sand after a new or replaced pump | Pump set too close to the bottom, or sized larger than the well can deliver | Have the contractor check pump depth and sizing — see sizing by GPM and head |
| Sand plus sputtering, air, or low pressure | Water level drawing down near the pump intake | Contractor; see low water pressure on a well |
| Rust-colored or black fines rather than grit | Iron, manganese, or pipe scale — not sand | Test the water; see iron in well water |
Sand is hard on submersible pumps, too. Grundfos SQ and SQE pumps are built to tolerate some sand, but no pump likes it, and a sand problem is worth fixing at the source. For pump questions, R.E. Merrill & Associates and Grundfos dealers can help — see SQ vs SQE.
How a spin-down filter works
Water enters a clear housing and spins, throwing heavier particles outward and down. A reusable mesh screen catches what is left. Grit settles at the bottom, and a ball valve or flush valve lets you dump it to a bucket or drain without shutting off the water.
- Mesh rating: lower mesh numbers are coarser. Pick one fine enough to catch your sand but not so fine it clogs every day; many homeowners start coarser and step finer.
- Flow rating: it should match or exceed your pump’s flow and pipe size so it does not become a restriction.
- Clear housing: lets you see when to flush. Keep it out of direct sun and protect it from freezing.
- Pressure rating: must exceed your pressure switch cut-out with margin.
Where to install it
- After the pressure tank and tank tee is the most common spot, ahead of the softener, cartridge filters, UV, or RO — check the filter maker’s instructions. See tank tee kits explained.
- With shutoffs on both sides so you can service the screen.
- With the flush outlet near a drain or where a bucket fits.
- Followed by finer filtration if needed — a spin-down catches grit, not fine silt; a cartridge filter after it handles finer particles.
Installing it in the supply line is plumbing work; use a licensed plumber or well contractor where code requires.
Upkeep
- Flush when you see grit collect — weekly at first until you learn your rate.
- Pull and rinse the screen a few times a year; replace a torn screen right away.
- Watch the gauge: a big pressure drop after the filter means it needs cleaning.
- If grit volume climbs over time, call the well contractor.
When to call a pro
- Sand appears suddenly, increases, or comes with air, sputtering, or low flow — licensed well contractor.
- You are replacing the pump, or think it is set too deep or sized wrong — licensed well contractor or Grundfos dealer.
- Cutting in the filter and shutoffs — licensed plumber where code requires.
Start with a licensed well contractor for sand problems and a licensed plumber for filter installation. R.E. Merrill & Associates has handled industrial and municipal pumps and fluid systems since 1987 and can talk through Grundfos well pumps — contact R.E. Merrill & Associates.
Related across the site
- Softener resin replacement — grit and iron shorten resin and valve life
- Leak sensors for the basement and well tank — catch a leaking filter housing early
Sources
- Sediment filter manufacturer instructions — mesh, flow, pressure rating, and installation.
- State well-construction programs and licensed well contractors — causes of sand pumping.
- Grundfos residential pump literature — sand tolerance and pump setting.