Water pump cycling but there is no leak

[W3GAC]

Set of new diaphragms not very expensive and should always have spare on board anyway. With spare it’s easy to quickly change out do see if problem goes away. All that said, some leaks are very hard to see/ find. Often a likely leak point (after all the obvious connections) is a chafe point that hard to get to/ see. Fingers are not all that sensitive to ‘wet’ so suggest you use a tissue and really go all the way around every inch of your plumbing (hot and cold) checking tissue frequency for dampness. A trick is to touch it to top of top lip which seems to be very sensitive to both moisture & the cooler temp of the wet tissue/ evaporation. Good luck finding it.

[Dick Manning]

This happened to me with a new Shurflow water pump. As RMES suggested, check your inlet and outlet hose connections for tightness/seal. On mine the inlet hose was sucking air even tho it would pump water to the sink.

[Squanderbucks]

Assuming you do not have a tank to buffer the water pressure then a pump cycling either has a leak on the pressurized side of the diaphragm or a faulty switch. If you had an actual leak in the output side then you would see your water tank being depleted.
With no water loss then the "leak" is inside the pump/switch apparatus.
First as suggested take apart and clean the switch mechanism. Do not use the silicone grease for impellers it will act as an electrical insulator and prevent good electrical flow. Use dielectric grease on the contacts or maybe some of your silicone just on any springs or pivot points for the contacts.
Still a problem remove diaphragm and pistons or seals and clean, inspect and replace. If you really want to know which item is the culprit do one at a time and see what happens. If you just want to get it done - replace diaphragm and seals with new kit.
If you do have an accumulator tank it may have filled with water and have too little of an air space above the diaphragm and need to be bled out and re-pressurized. This also will cause excess cycling. Check out You-tube for suggestions there.

[HopCar]

As has been stated there are valves in the pump that have gone bad.
The pump will run until pressure builds in the line and the pressure switch turns it off. Then the water leaks back through the pump to the tank side until the pressure has dropped enough to allow the pressure switch to turn on the pump. Over time as the valves deteriorate the interval between cycles will get shorter.

You can replace the diaphragm/valve assembly but do yourself a favor and replace the pump.

[wesevans]

If you have a demand system the problem may be the diaphragm in your accumulator tank.

[US1Fountain]

Whenever mine does that, its always the pumps diaphragm not seating and leaking back into the water tank. Have cleaned it before to get some more life out of it, but then decided if Im going to take it apart to clean, I'm going to just replace the diaphragm assembly and be done with it.
You can test the pump to know if it is the diaphragm leaking by closing the valve to the water tank. If the pump stops cycling, you found your problem.

[waterman46]

Originally Posted by meirriba

Check the air pressure system of the reservoir by the pump. It may be leaking and the pump tries to build pressure again whenever it feels pressure loss.

This probably is not the problem since if the reservoir was leaking it would soon fill up with water and then a leak of water to the outside would be apparent.

[US1Fountain]

Points to ponder

If there is air n the system, once the pump has ran and built up pressure it will stay off as the air has compressed. No different than an air compressor. It just kicks back on if there is a leak.

Since the op has stated he has no leaks, the water is going back into the water tank , by way of a non sealing valve in the pump. A loose fitting on the inlet side of pump will not cause it t cycle either. That’s on the front side of the check valve. Considering that the tank has an air vent, the supply side isn’t sealed

[phalo]

OK hd002e spill the beans, what did you find. After all the time I spent trying to solve a similar Shurflo problem to find it was none of the suggestions made to date but someone/thing had fiddled with the pressure setting. Though your manufacture date of 2002? does make other issues probable.

[Half Moon Ecat]

Consider checking the water piping from tank outflow to pump. Our boat had same issues: frequent cycling, but no visible water leaks. It turned out that a plastic 90* fitting on the top of the tank had a hairline crack. As it was before the pump, it was a vacuum flaw. The pump sensor kept trying to solve the low pressure. The solution was to replace the fitting. The rest of the system tested ok.