Water pump adjustment

[georgelesley]

We have a Shurflo 4008 bypass type pump that cycles on and off constantly no matter the flow rate demanded. The manual says the hi pressure setting might be too low. There is an adjustment on the pressure head.

Anyone ever do this, if so how sensitive is the adjustment, is the pump running to set it?

[DutchmenSport]

drsteve wrote:

westend wrote:
Most water pressure tanks I'm familiar with have an AIR bladder that serves to even water pressure inside the tank. The water is outside that bladder.

I think it's the other way around... the water is contained within the bladder. Flotec

Thanks drsteve. I've been around these pressure tanks all my life (I'm 61) Been battling the one in my mother's house (almost, since the day I was born. Replaced it 3 times in 61 years, and bled the thing and repressurized lots of times... I absolutely hate that thing!) But, it's a necessary evil if your house is on a well.

From the web site:
Q. I tried to check the air pressure in my tank and water came out of the valve. What’s that mean?
A. If you get water out of the air valve stem, it means your bladder has failed. Water has left the bladder and is up above it in the tank. It is now time to replace the bladder or the whole tank.

[Old-Biscuit]

Sam Spade wrote:

Old-Biscuit wrote:
......pump shutoff pressure is 55#

That is not universal and depends on what pump you have.

I think that most are nowhere near that high......but that is mostly a guess based on looking at a few replacements in catalogs.

OPs pump is Shurflo 4008 Model
Pressure switch set to shutoff at 55psi'
Bypass valve set to start opening at 40psi and to be fully open at 62#
(full open set point is higher so pump can reach shutoff set point and stop)

Information provided WAS based on OPs specific pump

[drsteve]

westend wrote:
Most water pressure tanks I'm familiar with have an AIR bladder that serves to even water pressure inside the tank. The water is outside that bladder.

I think it's the other way around... the water is contained within the bladder. Flotec

[georgelesley]

westend wrote:

About the only way to get around the constant pulsating on-off, is to add a pressure (air) in-line tank. The tank has air in it with a bladder that holds water. The air space outside the bladder keeps pressure on the bladder and thus, in your lines. It keeps the pump from turning on-off every time you open a faucet. But, when the pump comes on, it will run longer to fill the pressure tank. But also, you can run water until the pressure drops and the water pump turns on again.

Most water pressure tanks I'm familiar with have an AIR bladder that serves to even water pressure inside the tank. The water is outside that bladder.

The manual specifically says no accumulator tank needed. The bypass works just like the fuel pump in a car that sends unneeded fuel back to the fuel tank.

[westend]

About the only way to get around the constant pulsating on-off, is to add a pressure (air) in-line tank. The tank has air in it with a bladder that holds water. The air space outside the bladder keeps pressure on the bladder and thus, in your lines. It keeps the pump from turning on-off every time you open a faucet. But, when the pump comes on, it will run longer to fill the pressure tank. But also, you can run water until the pressure drops and the water pump turns on again.

Most water pressure tanks I'm familiar with have an AIR bladder that serves to even water pressure inside the tank. The water is outside that bladder.

[georgelesley]

The pump does not cycle when all water faucets are off. It cycles rapidly In very low water flow demands and slows when water demand increases. According to the manual, when operating correctly the pump should run evenly no matter water demand and bypass back into the tank unneeded water. That is why I suspect incorrect bypass and or hi pressure settings.

[DutchmenSport]

georgelesley wrote:
...no matter the flow rate demanded....

Does the pump cycle on-off faster and slower when the demand is more or less (when you open the faucet all the way, opposed to a very small trickle, or running the faucet in the kitchen and bathroom at the same time, opposed to running only 1 for example).

If so, then your pump is working perfectly normal. You do not have a pressure tank, so there is no air in the lines to compress causing an extra length of pressure. Your lines are all filled with water. They pressurize extremely quick, a teaspoon full of water can be enough to relieve the pressure enough for the pump to turn on.

You DID NOT say the pump is running when all faucets are turned off. This is correct? right? When faucets are all off, the pump shuts off and does not turn on??? right?

Clarify this and all the posts about about water leaks is a non issue.

If you are concerned about the fast, pulsating on-off of the water pump, THIS IS NORMAL. About the only way to get around the constant pulsating on-off, is to add a pressure (air) in-line tank. The tank has air in it with a bladder that holds water. The air space outside the bladder keeps pressure on the bladder and thus, in your lines. It keeps the pump from turning on-off every time you open a faucet. But, when the pump comes on, it will run longer to fill the pressure tank. But also, you can run water until the pressure drops and the water pump turns on again.

Please clarify? Does the pump run when all faucets are turned off?

[Sam_Spade]

Old-Biscuit wrote:
......pump shutoff pressure is 55#

That is not universal and depends on what pump you have.

I think that most are nowhere near that high......but that is mostly a guess based on looking at a few replacements in catalogs.

[Old-Biscuit]

TO test/adjust you need a pressure gauge on cold water system .......pump shutoff pressure is 55#

If you adjust shutoff pressure too high then bypass opening will keep pressure switch from making up ---pump will continue to run

Low flow/demand and pump 'chatter' (cycling on/off rapidly) could be bypass set to high (not opening soon enough...at 40#)

Got a pressure gauge you can use?

[Sam_Spade]

If it cycles ONLY when some water demand is present, that likely is normal.....or close to it. Or to put it another way, is the pump stops and stays off when there is NO demand, then there's not much you can do.

Often the plumbing lines are small and it takes a LOT of them open to make the pump run continuously.

[nineoaks2004]

I would check for a leak first, if it was working ok until this problem started...

[ScottG]

An expansion tank will tame your water pump a lot.

[ksg5000]

Not familiar with that particular water pump but in general a water pump that turns on when the faucets are turned off indicates that you have a small water leak in your plumbing ... I would rule that out first as water pumps are inexpensive .. replacing water logged wood is often very expensive. If you have outside shower .. suggest you start your investigation their.

[jules6]

Are you sure the pump needs an adjustment? You may have a small leak or the check valve is not seating properly. It will not have to leak very much to allow the pressure to bleed off.