Foot Valve
Valves / Check Valve / Non-Return ValveA foot valve is a check valve installed at the bottom of a suction pipe in a pump system, maintaining prime by preventing drain-back when the pump stops, essential for suction-lift applications where the pump is above the liquid source.
Working Principle
The foot valve is essentially a check valve (usually swing or ball type) mounted at the inlet of a suction pipe submerged in a tank, sump, or well. When the pump runs, suction lifts the foot valve disc off the seat, allowing liquid to flow up the suction pipe. When the pump stops, the liquid column in the suction pipe would drain back by gravity; the foot valve closes, trapping the liquid above it and maintaining the pump prime. Most foot valves include a strainer (screen) on the inlet to prevent debris from entering the suction pipe and damaging the pump. The strainer adds some inlet head loss, which must be accounted for in NPSH calculations.
Key Components
Body (threaded or flanged inlet), check mechanism (swing disc or ball), seat, inlet strainer/screen, lifting eye (for retrieval).
Types & Variants
| Type | Key Feature | Typical Use |
|---|---|---|
| Swing foot valve | Swing disc + strainer | Water wells, general suction lift |
| Ball foot valve | Rubber ball + strainer | Sewage, wastewater sump pumps |
| Heavy-duty foot valve | Robust construction for deep wells | Deep well pump systems |
| Flanged foot valve | Flanged inlet connection | Large industrial sump applications |
Common Materials
Body: cast iron (ASTM A126), bronze (ASTM B62), or 316SS. Disc/ball: bronze, rubber-coated steel, or 316SS. Strainer: perforated 316SS or bronze sheet. Seat: integral body metal or elastomer insert.
Applicable Standards
- API 594 (check valves, reference)
- MSS SP-71 (check valves, reference)
- AWWA C504 (reference for waterworks)
Industrial Applications
- Water well pump suction lines
- Sump pump and lift station intakes
- Fire pump suction from tanks or ponds
- Industrial process pump suction from sumps
- Cooling tower basin pump intakes
- Irrigation pump suction lines
Advantages & Disadvantages
Advantages
- Maintains pump prime — eliminates the need for priming on each startup
- Strainer protects pump from debris
- Simple and reliable — no external actuation or controls needed
- Available in materials for clean or dirty service
Disadvantages
- Adds inlet head loss (strainer restriction) — reduces available NPSH
- Submerged installation — difficult to inspect and maintain without pulling the suction pipe
- Strainer can clog, starving the pump of flow
- If the foot valve leaks, the pump loses prime and must be re-primed before starting
- Frozen foot valves in cold climates can crack the body
Selection Guide
- Size the foot valve at least one pipe size larger than the suction pipe to minimize strainer head loss
- Inspect and clean the strainer regularly — a clogged strainer is the most common cause of pump cavitation in suction-lift systems
- For deep well service, specify a heavy-duty foot valve with a positive seating mechanism to handle the high static head
- Install a primer line or vacuum priming system as backup in case the foot valve fails and the pump loses prime
- In cold climates, ensure the foot valve is below the frost line to prevent freezing
Practical Tips
- A clogged foot valve strainer causes the same symptoms as a failing pump — always check the strainer before condemning the pump
- Foot valve leakage is the most common cause of repeated pump priming problems. A simple test: fill the suction pipe, stop the pump, and observe if the pipe drains. If it does, the foot valve is leaking
FAQ
Does every pump need a foot valve?
No. Foot valves are only needed for suction-lift applications where the pump is above the liquid source and must maintain prime. For flooded-suction applications (pump below the liquid level), no foot valve is needed.
How do I know if my foot valve is leaking?
If the pump loses prime between runs (requires re-priming before starting), the foot valve is likely leaking. Confirm by filling the suction pipe with the pump stopped — if the pipe drains back, the foot valve seat is not holding.