water pump problems????

[sunrae]

I have just recently replaced my water pump to a shurflo 4008 pump. It is definitely a lot quieter than the original but now we are having issues with only the shower. The water pump will occasionally cavitate slowing the water flow. Not sure what the issue is as all the other taps and toilet are working fine. Have checked the lines for leaks and the hot water tank plug to make sure it is sealed tight. Any suggestions?

[Parrothead_Mike]

Try hooking up to city water rather than using the pump just to see what the flow is like. I'm not sure what that's going to show you, but it may indicate whether you have a problem with the shower head/plumbing or not.

[sunrae]

So finally got the trailer in to have the water pump looked at. They adjusted the pump pressure and seems to be working now.

Thanks for everyone's responses

[2oldman]

Hmm... perhaps try different flow rates through the shower and see what happens.

[partsman01]

Any thought of retrying the old pump, just to see what happens, maybe test the pressure it puts out, then hook up new one and see what pressure it puts out, plus in a marked container see what the flow is.

[Old-Biscuit]

Thumb wrote:

Old-Biscuit wrote:

Thumb wrote:
Sounds to me as though the new pump
is discharging more flow than the old pump
Cavitation results when a pump can discharge excessive volume that exceeds the
suction water supply and causes a drop in the required suction inlet pressure

Assuming you don't have other suction side leaks or pressure issues, this will help you

Install a shutoff valve on the discharge of your pump
and with the pump running and the shower turned on
slowly close the valve until the cavitation stops

Cavitation is caused by loss of suction head.....

Having the pump at too high of a distance above the fluid source
Having too small of a diameter of suction pipe
Having too long of a distance of suction pipe
Having too many fittings on the suction pipe
Handling a liquid with a low vapor pressure
Running the pump too fast

Most likely NOT an issue with OPs RV water pump.
The Surflo 4008 pump is a diaphragm pump and the diaphragm only moves 1/8"
OP states pump works properly on other faucets/toilet but has problem when shower is used.
Low flow/low demand....pump hitting pressure set point causing rapid cycling of pump.

I agree and All true except for the pump running too fast statement

The pump speed and the specific impeller design are matched by design
I spent many years doing that type of water systems product design and training

Loss of required head (pressure) at impeller , also known as Net Positive Suction Head
NPSHR, causes cavitation
Cavitation is characterized by the noise made by the imploding air bubbles that formed on the vanes of the impeller because of loss of required NPSH
But all of this is a mute point since learning that the pump is diaphram type
and no impeller used

I have eliminated what sounds like the same issue in a Cougar we used to own by doing as I suggested in my post but that pump had an impeller

Good luck with your issue, hope you get it fixed and back to camping in peace again

Happy 4th to all!!!
God bless America!!

Variable speed pump.........which some RV pumps are.
Although Not OPs

(30 yrs. Power Plant operator-----fully aware of NPSH)

[Thumb]

Old-Biscuit wrote:

Thumb wrote:
Sounds to me as though the new pump
is discharging more flow than the old pump
Cavitation results when a pump can discharge excessive volume that exceeds the
suction water supply and causes a drop in the required suction inlet pressure

Assuming you don't have other suction side leaks or pressure issues, this will help you

Install a shutoff valve on the discharge of your pump
and with the pump running and the shower turned on
slowly close the valve until the cavitation stops

Cavitation is caused by loss of suction head.....

Having the pump at too high of a distance above the fluid source
Having too small of a diameter of suction pipe
Having too long of a distance of suction pipe
Having too many fittings on the suction pipe
Handling a liquid with a low vapor pressure
Running the pump too fast

Most likely NOT an issue with OPs RV water pump.
The Surflo 4008 pump is a diaphragm pump and the diaphragm only moves 1/8"
OP states pump works properly on other faucets/toilet but has problem when shower is used.
Low flow/low demand....pump hitting pressure set point causing rapid cycling of pump.

I agree and All true except for the pump running too fast statement

The pump speed and the specific impeller design are matched by design
I spent many years doing that type of water systems product design and training

Loss of required head (pressure) at impeller , also known as Net Positive Suction Head
NPSHR, causes cavitation
Cavitation is characterized by the noise made by the imploding air bubbles that formed on the vanes of the impeller because of loss of required NPSH
But all of this is a mute point since learning that the pump is diaphram type
and no impeller used

I have eliminated what sounds like the same issue in a Cougar we used to own by doing as I suggested in my post but that pump had an impeller

Good luck with your issue, hope you get it fixed and back to camping in peace again

Happy 4th to all!!!
God bless America!!

[Old-Biscuit]

Thumb wrote:
Sounds to me as though the new pump
is discharging more flow than the old pump
Cavitation results when a pump can discharge excessive volume that exceeds the
suction water supply and causes a drop in the required suction inlet pressure

Assuming you don't have other suction side leaks or pressure issues, this will help you

Install a shutoff valve on the discharge of your pump
and with the pump running and the shower turned on
slowly close the valve until the cavitation stops

Cavitation is caused by loss of suction head.....

Having the pump at too high of a distance above the fluid source
Having too small of a diameter of suction pipe
Having too long of a distance of suction pipe
Having too many fittings on the suction pipe
Handling a liquid with a low vapor pressure
Running the pump too fast

Most likely NOT an issue with OPs RV water pump.
The Surflo 4008 pump is a diaphragm pump and the diaphragm only moves 1/8"
OP states pump works properly on other faucets/toilet but has problem when shower is used.
Low flow/low demand....pump hitting pressure set point causing rapid cycling of pump.

[Thumb]

Sounds to me as though the new pump
is discharging more flow than the old pump
Cavitation results when a pump can discharge excessive volume that exceeds the
suction water supply and causes a drop in the required suction inlet pressure

Assuming you don't have other suction side leaks or pressure issues, this will help you

Install a shutoff valve on the discharge of your pump
and with the pump running and the shower turned on
slowly close the valve until the cavitation stops

[Old-Biscuit]

Have you disconnected the shower hose at faucet and then tried running pump.....some hand held showers have flow restricters in the end of hose.

IF pump still 'stumbles' with hose off and shower faucet knob fully open then pump may need a slight adjustment (on end of pump.center screw turn it clockwise 1/2 turn)

If pump runs flat out with hose off of shower faucet..then drill out/remove restricter in end of hose (or leave with it)

[Dakota98]

Once resolved, please post your findings.

[sunrae]

Yes, we did all this already. I think it is time to take to the dealers. We just thought maybe someone had the same problem at one time and it was an easy fix. Oh well. Can't say we didn't try everything.

[Dakota98]

Working backwards then. The next step would be the valve controlling the shower head.

I hope someone comes up with a better idea than mine.

Also maybe. check the outside shower controls, if you have them.

[sunrae]

Yes we did this thinking that maybe the shower head was plugged but it was still doing the same.

Thanks

[Dakota98]

Doesn't make sense at all.

Maybe remove the shower head & try the pump then.