Diagnosing Recurring Pump Prime Loss After Check Valve Replacement

A pump holds 40 PSI overnight but loses prime by morning's first use. The homeowner recently switched from PVC to brass check valves, suspecting the change introduced the problem.

Root Cause Analysis

Prime loss indicates air entering the suction line between pump and water source. Since the issue began after check valve replacement, focus inspection there:

• Male adapter connections: Check for leaks at all threaded joints
• Thread sealant: Teflon tape or pipe dope is essential—missing sealant allows air intrusion
• Hose bib at pump: Must be completely closed
• Screen/canister: If damaged, debris can hold check valve open—replace if compromised

Systematic Troubleshooting

1. Pressurize system and apply soapy water to all suction-side joints—bubbles reveal leaks
2. Verify check valve orientation (flow arrow toward pump)
3. Inspect foot valve/strainer at water source for damage or blockage
4. Confirm pump housing gaskets seal properly

Even small air leaks prevent prime retention. Brass valves require proper threading technique—clean threads, adequate Teflon tape (3-4 wraps), and proper tightening without over-torquing.