Diagnosis
A leak from the pump body itself is usually from one of two seals: the pump head O-ring or the seal around the piston. Both are wear items, especially if the unit was ever run without water, even briefly.
How to Fix It
For the pump head O-ring, you can sometimes fix it without major disassembly. The head is held on by several bolts. If you're handy, you can unbolt it, replace the large flat O-ring inside (check for nicks or flat spots), re-tighten the bolts evenly in a criss-cross pattern, and see if that stops the leak.
If That Didn't Work
If the leak is coming from around the piston shaft (you'll see water weeping from where a shiny rod goes into the pump), that's the shaft seal. Replacing that requires a full pump teardown and is generally considered a major repair.
Heads Up
Don't ignore a pump body leak. Water getting into the motor or electronics compartment can cause a short circuit, which is a safety hazard and will kill the machine.