Hi guys. I posted my problem a while back but didnt get alot of reponse and i cant seem to find the original post. Anyways I have a 2014 Attitude 27CBG. I have the Shurflo Revolution 4008 model water pump. I noticed one day that while running the gen when i have the water fully open..wether in kitchen, bath or shower, the pump would surge and the pump would sound likes its turning on and off. So i blamed it on a bad water pump and the dealer replaced it. Well the pump still surges when the gen is on..When I turn off the gen..it would surge on and off for a little and after a while it would flow at a constant even flow..(im testing it with faucet fully open). So not sure whats causing this..is it an electrical issue? is the gen not providing the pump enough power or too much power?? One thing that might be linked or maybe not is my first trip out with the TH..i stated the AC with the gen on and the gen died..i tried to turn on gen again . it would start for 1 min then die again..they told me it was a bad fuel pump and replaced it and it works fine now..but not sure if that has anything to do it the water pump and the electrical?? maybe maybe not..Here is a video of what it looks and sounds like..thkshttp://s43.photobucket.com/user/Rockinfigs/media/20130609_151521.mp4.html

Without the gen running the voltage to the water pump will be about 12.5 . With gen running the voltage will be 13.6 . At the higher voltage the pump runs faster and can push more water than the demand and will turn off and on. At the lower voltage it can't keep up with the demand and nevr shuts off.

so is that normal? should i not worry about it?

Agree with the diagnosis, and that it is normal.

A surging water pump is not normal.Every RV I purchased I have had to adjust the pressure switch on the water pump.After that, no more surging, even with a faucet opened only half way.Also has nothing to do with voltage since the pressure switch is affected by water pressure and not voltage.

Water Pump Problem Need Help! | Good Sam Community

19 Replies

Rockinfigs
Explorer
Jun 14, 2013
wa8yxm wrote:
Ok, it "Surges" when the generator is on but not when off.. This makes 100% sense, here is what is happening.

The capacity of the pump is greater than the capacity of the faucet, There *IS* an accumulator of sorts in the line, (NOTE you may have an aux accumulator tank but if you do not the water heater acts as one).

Generator running:

So when pressure drops, the pump kicks in and "Surges" (It is controlled by a pressure switch after all) pumps the tank back up to full pressure and then it cuts out (normal operation) then as the pressure drops. it kicks back in.

NOW: when the generator is off...

Battery voltage is lower than converter voltage (has to be or the batteries would not charge) so now when the pressure drops and the switch calls for the pump, the pump is not quite as "Fast" as it was on the converter, so it does not pump faster than the faucet can faucet, thus it does not shut off till you turn off the faucet.

Normal operation for a pressure switch controlled pump.

So would u say this is normal behavior and I shouldn't worry?
wa8yxm
Explorer III
Jun 14, 2013
Ok, it "Surges" when the generator is on but not when off.. This makes 100% sense, here is what is happening.

The capacity of the pump is greater than the capacity of the faucet, There *IS* an accumulator of sorts in the line, (NOTE you may have an aux accumulator tank but if you do not the water heater acts as one).

Generator running:

So when pressure drops, the pump kicks in and "Surges" (It is controlled by a pressure switch after all) pumps the tank back up to full pressure and then it cuts out (normal operation) then as the pressure drops. it kicks back in.

NOW: when the generator is off...

Battery voltage is lower than converter voltage (has to be or the batteries would not charge) so now when the pressure drops and the switch calls for the pump, the pump is not quite as "Fast" as it was on the converter, so it does not pump faster than the faucet can faucet, thus it does not shut off till you turn off the faucet.

Normal operation for a pressure switch controlled pump.
liberty2010
Explorer
Jun 13, 2013
I am late to this party also. Our 4008 pump will burp once about every 5 min. no water leaks etc. I see 2 adj screws on the head one on the bumped out part with the power wires and the other below that. Which one is the pump pressure and which one is the cut off pressure. My guess in the one nearest the wires is the cutoff but do not know. Thanks
Rockinfigs
Explorer
Jun 13, 2013
Ok so I tested with shore power at my house n it does surge... So if the volt is higher n it affects water pump motor speed is it normal for it to surge w gen or shore power? Should I even mess with and adjust the pressure switch screw? Remember this problem doesn't exist on batt power
aruba5er
Explorer
Jun 13, 2013
Late to this party but I'd check with a VOM the voltage at the pump- plugged into shore power and also with generaator and also on battery only (shore power/ Generator Both off. The higher voltage will affect the speed of the motor
RoyB
Explorer III
Jun 13, 2013
I saw the photos on-line of the ONAN - Should not be any difference between that ONAN and regular shore power. Your water PUMP is definitely getting higher DC VOLTAGE when running off the generator as I described above.

I'm sure the other ideas may help in this setup as well... It all has to do with how the lines are pressured up. You may have some leakage with the one way valves or like others have said the water pump pressure value could be set differently maybe... The accumulator tank is a great idea to stabilize things. Even LOWES has such a tank that will work.

Of course the water pump is only used when feeding water to you system from the fresh water tank. You dont need to run the water pump when connected to city water... Maybe you are low on water in the fresh water tank?

Here is a simplified water flow diagram on how the RV Trailer water system works...

Its hard to work on someones elses unique problems.. All we can is submit all the different ideas for you to ponder on and hopefully can come up with a fix...

I'm just trying to submit different ideas of what others have said before that may apply to your particular problem...

Roy Ken
Rockinfigs
Explorer
Jun 13, 2013
I have the Onan.. I think 4k gen..I have not checked while on full hook up.. Il test it out at home today n let u know.. But right now it only does it while gen is on
RoyB
Explorer III
Jun 13, 2013
You may need to add an accumulator tank in-line with the water pump to level things out somewhat. This one shown is from PPL...

Larger accumulator tanks are available

Looks like you have plenty of room around your water pump...

just another thought
Roy Ken
RoyB
Explorer III
Jun 13, 2013
There should not be any difference between using your generator and the shore power from a 120VAC Electrical receptacle source.

Does this same thing when you are hooked up to a regular shore power connection?

Perhaps the 60Hz waveform from the generator is not as good as it should be... What generator are you using...

You may have a couple of issues here...

Roy Ken
Rockinfigs
Explorer
Jun 13, 2013
When I have the gen running and turn on kitchen, bath or shower on full the water surges n the pump seems like it's turning on and off o and off on and off... I posted a video of what's exactly happened on my original post.. I really have no idea what's causing this. Again this is when gen is on only