A sump pump making a loud banging or clanking noise immediately after it finishes running and turns off is typically caused by water hammer resulting from a standard swing check valve slamming shut violently. When the pump motor shuts off, the heavy column of water remaining in the vertical discharge pipe crashes downward under gravity against the check valve flapper, creating a shockwave through your plumbing pipes. Verification: Replace the standard swing check valve with a modern spring-loaded check valve designed to absorb shock and close silently.
1 votes
Marked as accepted