Short definition
A foot valve is a one-way check valve installed at the bottom of a well-pump suction pipe, with a screen to keep debris out. Its job is to hold the pump’s prime — without it, water in the suction pipe drains back into the well between cycles and the pump can’t restart in the morning. Standard on jet-pump (above-ground or shallow-well) installations.
What it is
The foot valve is a brass or plastic body with a spring- or gravity-loaded check disc and an integrated strainer screen. It sits at the bottom of the suction pipe, submerged in the well water. When the pump runs, the disc opens and water flows up the pipe; when the pump stops, the disc closes against the upward column of water and prevents it from draining back down into the well.
The strainer keeps sand, silt, iron particles, and other debris from being drawn up into the pump where they would damage the impeller and other components.
Foot valves are most common on jet-pump installations — above-ground pumps or shallow-well configurations where the pump is at the surface and the suction pipe extends down into the water. Submersible pumps (where the pump itself sits below water in the well) often use a built-in check valve at the discharge instead, but some installations include both for redundancy.
Why it matters to a homeowner
If you’re on a private well with a jet pump, the foot valve is what makes the pump able to start each morning. When it fails, the symptoms are immediately recognizable:
- Pump won’t start in the morning. The diagnostic test is to pour water into the pump’s prime port and see whether it holds prime — if water audibly drains down into the well, the foot valve is letting it back-drain.
- Slow well refill, low GPM at fixtures. Strainer clogged with sand, silt, or iron particulates.
- Pump short-cycles. Disc partially stuck open by debris — same as failed.
- Iron-water staining at fixtures. Strainer not catching enough fine particulates; combined with point-of-use filtration as the typical fix.
Replacement requires pulling the suction pipe out of the well — straightforward on shallow wells, more involved on deeper installations. Brass foot valves last longer than plastic; iron-rich water (common in WA Olympic Peninsula and Mason County wells) is hard on either material and may require more frequent replacement.
Common failure modes
- Disc or O-ring degradation — slow back-drain, pump loses prime overnight.
- Strainer clogged with sand, silt, or iron — restricts inflow, low GPM.
- Disc stuck open by debris — same as failed.
- Spring fatigue on spring-loaded foot valves — slow drainback.
Washington note
WA private wells are concentrated in rural Mason, Whatcom, Jefferson, Kitsap, Olympic Peninsula, San Juans, and east-of-Cascades agricultural counties. Jet-pump installations are especially common on shallow wells in those areas, and foot valves are routine maintenance items. Iron- and sand-rich water in some of those aquifers (Olympic Peninsula and Mason County in particular) accelerates strainer fouling and may push the foot valve into a 5–10 year replacement cycle versus the longer life it would see on cleaner water.