I have a Flotec jet pump that's maybe 7 years old, and it's short cycling. The weird thing is that it doesn't happen when water is running -- then it runs full-out. But when the water isn't running at all, it short cycles, very fast. I can't understand the principle of what would cause that.

Now, confession time: I don't have a pressure tank in this system. It's running the water for an RV, and I replaced an RV pump with this one 7 years ago and didn't know that this kind of pump is supposed to run with a pressure tank. So, yes, I know the advice is to put in a pressure tank, and in fact I've got one on the way. But it's going to be a pretty big nuisance, because I don't have a great place to put it, so I'd much prefer not to install it. And -- the system worked fine for 7 years.

I already tried replacing the pressure switch, and that didn't change the behavior.

So, my questions are:
1. What would cause short cycling when no taps are open and no water is running?

2. Why do RV pumps not require a pressure tank when jet pumps do?

3. Is there any way of solving this problem without putting in a pressure tank?

 

Welcome to the forums.


1. What would cause short cycling when no taps are open and no water is running? A leak.

2. Why do RV pumps not require a pressure tank when jet pumps do? When you turn the water on in an RV.... the pumps starts immediately. If there was a leak the RV pump would cycle too.

3. Is there any way of solving this problem without putting in a pressure tank? Find and fix the leak.


Since this a well water system you could also have a problem with your footvalve/checkvalve depending on your system..... allowing water to leak back into the well.

 

Before I got your message, I hosed out the inside of the pump and that solved it. So apparently the problem was some bit of crud affecting the little hose going to the pressure switch.

So now it does short cycle some while running into the trailer, but it doesn't short cycle when the water is off. Which is what the behavior has been for years. Perhaps I'll get ambitious and install that pressure tank someday, but for now, I've got what I wanted. Hooray.

 

Your pump is providing more than is being used, thus the short cycling. May be a larger than normal pump. Yeah, a tank would eliminate that.

 

OK, so it's no longer short cycling when there's no water running. BUT -- when I run the water for a while, eventually the pump turns off, and then it takes it a while for it to wake up and turn back on. The water stops completely in the meantime. What could the problem be now?

 

You previously mentioned a plugged tube to the pressure switch. If the pressure switch can't read the proper water pressure it won't know when to turn on.

When you don't have water.... check and see if the pressure switch is open or closed.

 

Adding a pressure tank will improve the operation of any sealed (non-gravity) well system that did not come with a pressure tank.

You may have gotten away with no pressure tank because there used to be a reasonably large spread between pump turn on pressure and pump turn off pressure. Too small a spread, possibly resulting from a clogged pressure switch, can increase the amount of short cycling.

 

How far is the RV from the pump? Is it connected by a long garden hose? Without a pressure tank the pump is supplying pressurized water to a very small "container". Without a surge tank to absorb fluctuations, water hammer can cause the pressure switch to rapidly cycle. A long spongy garden hose can absorb the impacts and reduce the problem, but a tank is the right way to go.
Short-cycling will reduce the life of the pump motor & switch.

 

Yep, just added a small pressure tank and it has solved the problem. It's still a bit mysterious why it worked for me in the past, but in any case, the problem is solved. Thanks for your help.