We are on a well with a submersible pump and bladder tank. Our pressure is set to 20/40.

A few days ago I noticed the pump was short cycling, ie would run about 5-10 secs, shut off for 5-10 secs and then repeat. I checked the bladder tank and it had no air in it so I recharged it.

I listened today to see how much it was cycling. I was filling the washing machine and the pump would run about 20 secs, shut off for about 40 secs and then run again for about 20 secs. From what I've read the pump should be running for closer to a minute.

Unfortunately my water pressure gauge is broken so I can't verify the pressures the pump is turning on/off at.

What should I be looking for/checking?

 

Let's start with what pressure you pumped the tank up to; it should be 2 psi below cut-on pressure, i.e. 18 psi in your case. Also, that should be done with the water side of the system depressurized, i.e. turn off pump and open a faucet.

 

18 psi in the tank when power is off and all water is drained. then power back on and close main valve. it should build to 40 and cut off. with main valve closed and pump switch kicked off at 40.. make sure it holds the pressure... then cut the main valve back on and let it rock.

depending on your pump model and tank size, it may be correct now. i've been putting constant pressure valves on my subs with 20 gal tanks lately, so you dont have to worry about the cycling when using steady water. also, a gauge costs like 5 bucks, grab another when you get a chance... but you can still get an accurate reading from checking the tank. check the tank with a tire gauge when pump kicks on, and again when pump builds and cuts off.. thats your cutin/cutout pressure. then drain and adjust your tank according.

 

I picked up a new gauge today and will be putting in on this weekend. I am also going to get a new Schrader valve just in case that is where my air leaked out.

I don't know the tank size, it doesn't say on it anywhere that I can find. It is about 24" in diameter and about 36" tall, might be a little shorter. (This is from memory and not actually measured.)

What is a constant pressure valve?

 

The constant pressure valve basically does what it's name says. It keeps a constant pressure on the output. Your system's pressure will rise and fall as the pump cycles on/off. The constant pressure valve will let water out at a constant 20 psi for example. You may notice the constant pressure when taking a shower but it does not directly correct the short cycling of your pump.

 

sounds like u have somewhere around 20-30gal bladder tank. lets say you have a 20 gal tank with 40 psi constant pressure valve and switch set to 30-50.. your pump will still kick on when 6~ gallons of water is used from your system and pressure drops to 30 just like it will now.. however, when pump kicks on and pressure reaches 40 psi, the valve will close and only allow 1-2 gpm to fill the tank until 50 psi shut off is reached so you can use however much water over 1-2gpm that your pump can handle and the pump will run solid, and the demanded water will stay at 40 psi.. showers/laundry/irrigating/etc. pumps are rated for continuous duty, and only require 1 gpm to stay cool.. cycling is what kills a motor.

in the end, nothing can top a pump with a properly sized tank imo, but you rarely see them sized correctly anymore for lack of knowledge, huge footprints, and are more costly. CPV is a good product imo and does eliminate cycling.. when water is in demand.

about properly sized tanks without the CPV.. according to flexcon, their 32gal tank has a drawdown of 10.9gal when set 30-50psi. so a 10 gpm pump would run about 1 minute during a cycle, and i would call that on the smaller side.

 

Thanks for the explanation, justwater. This is all helping me understand how this all works.