Pump troubleshooting
Water is leaking from under my pump
A puddle or steady drip coming from underneath the pump, right where the motor meets the pump housing, is one of the more common pump faults. In most cases it’s the mechanical seal.
What the mechanical seal does
Where the motor shaft enters the wet part of the pump, a mechanical seal keeps water in and air out while letting the shaft spin. It’s a wear item: over years, or after running dry, the seal faces wear and it starts to weep.
How to tell it’s the seal
- The drip comes from the joint between the motor and the pump body, not from a pipe fitting.
- It’s worse while the pump runs and under pressure.
- The fittings themselves are dry and tight.
What to do
Rule out the easy stuff first: check the pipe unions and the drain or priming plugs are tight, as a weeping fitting can look like a seal leak. If it really is the seal, it’s a replacement rather than a repair. A seal kit and a careful hand can do it on many pumps; otherwise a pump service agent will. A seal that has failed after a dry run is a sign the pump lost prime or ran short of water, so fix that cause too.
Safety: Isolate the power before touching a leaking pump. Water and electricity together are dangerous.
Common questions
What makes a mechanical seal fail?
Age and running dry are the big two. Even a brief dry run overheats the seal faces and can ruin them, which is why priming and never running the pump dry matter so much.