Pump cycling......lose of line pressure
Leak at fitting(s)
Leak thru check valve (pump internal one or city water connection one)
Leak thru low point drain valve(s)
Leak thru toilet water valve
Leak at faucet
Leak from Pressure Relief Valve
And just due to hot water side cooling off.
Rapid cycling (every few seconds) major leak
Occasional cycling (every few minutes) minor leak
Every once in awhile (hour-hours-days) very small leak
The real question is WHERE is leaking.
If NOT at a fitting etc. and just thru check valve......ignore/replace pump internal/add in-line on pump discharge line----if city water connection check valve......replace assembly OR screw a 3/4" PVC plug into connection.