A pump that loses its prime overnight is rarely a bad pump. It is usually a two dollar flap sitting twenty feet underwater.
The foot valve is the least glamorous part of a suction system and the one that strands more homeowners than any other.
What Is a Foot Valve?
A foot valve is a check valve fitted to the bottom of a suction line, usually with a built-in strainer. It lets water flow up toward the pump and closes as soon as flow stops, keeping the suction pipe full so the pump never has to start against air.
Key Takeaways
- The foot valve holds prime, the strainer keeps debris out.
- It sits at the bottom of the suction pipe, not at the pump.
- Only suction pumps need one, submersibles do not.
- A pump that loses prime overnight points straight at it.
- Replacing one means pulling the whole suction line.
Foot Valve or In-Line Check Valve?
| Foot valve | In-line check valve | |
|---|---|---|
| Location | Bottom of suction pipe | At or near the pump |
| Holds prime in | The whole suction line | The pump and casing only |
| Strainer | Usually integral | None |
| To service | Pull the pipe | Unbolt at the pump |
| Best for | Wells and cisterns | Backup, or short lifts |
Fitting a check valve at the pump instead of a foot valve is a common shortcut, and it half works. The pump stays wet, but the suction pipe still drains, so the pump has to pull that column back up on every start. General valve mechanics are covered in this reference on the check valve.
Signs Yours Has Failed
- Prime lost overnight but the pump runs fine once primed.
- Water audibly draining back down the pipe after shutdown.
- Long, noisy starts while the pump clears air.
- Sand in the pump if the strainer has broken away.
- Pressure that builds, then vanishes between uses.
The overnight test settles it. Prime the pump, shut everything down, and check in the morning. If prime is gone with no leak above ground, the valve is not holding, and the priming procedure itself is in our shallow well jet pump guide.
Why a Failed Valve Wrecks Pumps
Losing prime is not just an inconvenience. A suction pump that starts dry has no liquid film between its seal faces, and that film is the only thing keeping them from welding themselves together.
A few dry starts will finish a seal that had years left, as explained in our guide to the pump mechanical seal. Sand from a broken strainer does the same to the impeller, which we cover in the pump impeller guide.
Choosing a Replacement
Match the pipe size and the material to what the well actually holds. Brass and stainless bodies outlast plastic in gritty water, and a stainless strainer basket will not crumble the way a plastic one does after a decade underwater.
Given the labor of pulling the line, buying the cheapest valve available is a false economy. Size the strainer openings small enough to protect the impeller but large enough that they do not starve the pump, and check the well itself if grit is the recurring problem, as covered in what a change in well water is telling you.
Frequently Asked Questions
What is a foot valve for?
A foot valve is for holding a pump’s prime. It is a check valve fitted to the bottom of the suction line, usually with a strainer built in, and it closes the moment flow stops so the suction pipe stays full of water. Without one the water drains back down the well between cycles.
What happens when the foot valve goes bad?
When a foot valve goes bad the suction line drains back after the pump shuts off, so the pump loses prime and starts against air. You get long noisy starts, prime gone by morning, and pressure that builds then vanishes. If the strainer has broken away, sand starts reaching the impeller as well.
What’s the difference between a check valve and a foot valve?
The difference is position and what each one protects. A foot valve is a check valve with a strainer placed at the bottom of the suction pipe, so it holds the entire suction line full. An ordinary in-line check valve sits at the pump and keeps only the pump and casing wet.
Can a pump work without a foot valve?
A pump can work without a foot valve only if something else holds the prime, such as a check valve at the pump on a very short lift. On a well or cistern the suction line drains back without one, so the pump has to be primed by hand before every single start.
How do you check if a foot valve is working?
Check a foot valve by priming the pump, shutting everything down and leaving it overnight. If prime is gone in the morning with no visible leak anywhere above ground, the valve is not holding its seat. Listening at the wellhead for water draining back down the pipe in the moments right after shutdown confirms the same thing without waiting overnight.
Foot Valves and Suction Parts at Ken’s Distributing
Ken’s Distributing carries foot valves, strainers and check valves in brass, stainless and plastic to suit the Franklin Electric range and the Monarch water pump range.
Tell us the suction pipe size, the lift and what the water carries, and we will spec the valve and strainer together rather than sending whatever fits the thread.