Do ALL Rv's do this? If I leave the water pump on..

These systems are designed to hold pressure, with the pump pressurizing the system. It should stay that way until such time that you open a faucet, depressurizing the system and starting the pump.

Momentary (or extended) pump runs while the faucets are off generally mean that there is something allowing the pressure in the system to go down. Often this means a leak in the pipes or faucets. If so, you should find a tell-tale puddle someplace. If your system has cut-offs below sinks, etc., you can use them to help isolate the problem.

Another cause of this kind of failure can be within the pump itself. If the diaphragm is damaged, it can allow a very small amount of water to escape backwards through the pump, and you will be unable to locate any tell-tale puddle of water. The damage can result from even a small grain of sand stuck in the diaphragm. It is for this reason that RVs (should) have a small strainer installed between the pump and the fresh-water tank, like this one:



Ok, so your process should go like this:

1. Check for leaks in pipes, valves, and faucets. This will require some crawling around and feeling for a small bit of unexplained water.

2. Check the pump itself. If it is bad, order a new one along with a strainer to locate between the pump and the fresh-water tank.

:)
Lynn

ok, detective work it is thanks everyone :)

to clarify: it will run a bit when I'm NOT using the pump...if it's left on, but not used.

Have had 6 trailer and never had the problem you are mentioning. Leave the pump on day and night and it only cycles when tap is turned on. Agree with others that you have a slight leak somewhere.

I am guessing that when you say "keep the water off" you mean that you keep the water pump switch in the "off" position. If your pump short cycles, it is an indication that your system is losing water pressure. This can be caused by a small leak in the piping, a check valve in the system not holding, or some other lose of pressure. You need to do a little detective work and trace your lines to see if you have a leak.

If you have no obvious leak, my WAG would be that the check valve that prevents the water from back flowing into your supply tank is seeping back by.

I have never noticed short cycling in any of my RVs.

I think I'm a little confused by your question..(I am often confused).

The pump will run until the system is pressurized. If there is a leak somewhere it will run continuously in an attempt to pressurize itself.

Running for a second or two after you shut off a faucet is normal.

They are demand pumps. Designed to run when you turn on the faucet. More expensive pumps or adding a surge tank can make it a little more home like. If it runs periodically when all is turned of...you may have a leak somewhere.