Check Valve

A check valve is a one-directional flow control valve that allows water to flow in one direction only. In a private well system, check valves prevent water from flowing backward — back down the drop pipe into the well, or back from the pressure tank toward the pump — when the pump shuts off. Without check valves, the pressure system would lose its charge every time the pump stopped, and the pump would have to fight hydraulic backpressure to prime itself at every start.

Where Check Valves Are Located in a Well System

Most residential submersible pump systems have at least one check valve built into the pump assembly itself, just above the pump discharge port. This valve prevents the water column in the drop pipe from flowing back down into the well when the pump shuts off. Without it, the entire water column above the pump would drain back into the well, depressurizing the system and forcing the pump to re-lift that water weight from a standing start every cycle.

Many systems also have additional check valves installed in the drop pipe at one or more intervals, particularly in deep wells. These staged check valves prevent the entire water column from dropping at once if the bottom check valve fails. Above ground, a check valve may also be installed at the pressure tank inlet to prevent backflow from the tank toward the pump during system pressure equalization.

How Check Valve Failure Presents

Check valve failure is often subtle and easy to mistake for other problems. When the pump-end check valve fails, the drop pipe column drains back into the well each time the pump shuts off. The pressure system depressurizes partially or fully between pump cycles. The most common symptom is a slow pressure loss after the pump shuts off — the system goes from operating pressure to near-zero more quickly than normal, and the pump starts again more frequently than it should.

This pattern can look very similar to a waterlogged pressure tank (a failed pressure tank bladder), because both problems result in the pump short cycling. The diagnostic distinction: with a failed tank bladder, the pressure drop is immediate when the pump shuts off. With a failed check valve, the drop is gradual as the water column slowly recedes. A contractor can test this by monitoring system pressure over a period of minutes after the pump shuts off.

Another sign of check valve failure is the pump taking longer than normal to build pressure when it starts — the pump is working to lift the entire water column from a lower starting point than normal, rather than just topping off a pressurized system.

Replacement and Repair

Check valves are not expensive as parts go — a quality residential check valve typically costs $10 to $50 depending on size and material. However, the pump-end check valve is the most critical and the most commonly failed one, and accessing it means pulling the pump assembly from the well. For a submersible pump, that requires a pump truck and involves pulling the full drop pipe, pump, and power cable — so labor is the dominant cost.

If a pump is being pulled for any other reason — pump replacement, inspection, or service — the check valve or valves should always be inspected and replaced if there is any doubt about their condition. Replacing a worn check valve during an already-open service job costs relatively little compared to pulling the pump again to address a check valve that fails shortly after.

Check Valves and Well Warranty Coverage

Check valves that are integral to the pump assembly are generally considered part of the pump system and may be covered under well protection plans that cover the pump and its associated components. Above-ground inline check valves may also be covered depending on the plan's covered component list. Review your plan terms for specific component coverage language.