Troubleshooting Lost Prime in Lake-Fed Irrigation Systems

Why Your Lake-Fed Pump Loses Prime

If your lake-fed irrigation system suddenly loses prime after maintenance, the culprit is often a missing or faulty foot valve at the intake end of the suction line. A foot valve (a type of check valve) prevents water from draining back into the lake when the pump shuts off, keeping the suction line full and ready for the next start.

Locating the Foot Valve

In a properly designed system, the foot valve sits at the very end of the suction pipe submerged in the lake. If your system was homeowner-built and lacks a visible ball valve or check valve near the pump, the foot valve is likely the only one-way valve in the circuit. Over time, these valves can become clogged with debris, stuck open, or simply wear out.

How to Re-prime the System

1. Inspect the foot valve: Retrieve the intake pipe from the lake and check the foot valve for debris, damage, or a stuck flapper. Clean or replace it as needed.
2. Verify suction-line integrity: Ensure all threaded fittings and unions on the suction line are airtight. Even a tiny leak will prevent priming.
3. Prime the pump: Remove a plug or fitting on the pump casing or the discharge tee. Pour water into the opening until the suction line and pump housing are completely full. Replace the plug quickly.
4. Start the pump: Turn the pump on. It should build pressure within a minute. If it doesn't, repeat the priming process and re-check for leaks.

Preventive Tips

• Install a foot valve with a built-in screen to keep debris out.
• Support the suction line so it doesn't rest on the lake bottom where it can suck in sediment.
• Consider adding a priming port with a valve near the pump for easier future priming.

With a functioning foot valve and a leak-free suction line, your lake-fed system should hold prime reliably between cycles.