I have a class B with a nearly new pump (Shurflo 4008, installed about 1 year ago). Even with the bypass, running the sink caused pump cycling to a degree though not as bad as it was with the old 3 chamber pump. I decided to add a small accumulator to smooth out the flow and reduce cycling; even though I know the bypass and the accumulator both are designed to accomplish the same thing.Now, when running the sink (even at very low output) the water flow is smooth and the pump cycles normally and acceptably. However, occasionally when you turn the tap off, the pump hammers on and off for about 1-1.5 seconds quite loudly. It probably cycles 7 or 8 times until it hits pressure and shuts off.I'm wondering what I could do to correct this, and if anyone can assess what the cause may be. Thanks in advance!

The two most common accumulator tanks are the littler plastic one and the larger steel one. I installed the larger one in my MH and all has been fine with it. I'll install another larger one in my TT in the spring when it's warm outside again.With the larger ones you have to set the air pressure in the bladder. In the four years it's been installed, I've had to re-pressure the bladder once. Does the smaller one also need to be pressurized and did you do it?Bill

:) Hi, if your pump continues to cycle, you might have a small leak somewhere or air in the lines. If you haven't already done this, I would suggest that you install flex hoses to the pump.

Trackrig wrote:The two most common accumulator tanks are the littler plastic one and the larger steel one. I installed the larger one in my MH and all has been fine with it. I'll install another larger one in my TT in the spring when it's warm outside again.With the larger ones you have to set the air pressure in the bladder. In the four years it's been installed, I've had to re-pressure the bladder once. Does the smaller one also need to be pressurized and did you do it?BillSmall plastic. Do you also use a bypass pump? My accumulator was factory pressurized and I checked the pressure and it's good. You can feel it working, you get a nice steady stream when the pump turns off.

I'm not sure what you mean by a bypass pump? I'm using the Shurflow pump that was already in the MH's water system.Bill

If the 4008 pump keeps running slowly after the pressure is up, I can't believe it didn't have the same problem before you installed the bladder tank.The problem is common on that bypass type pump, and is easily corrected by adjusting it, by turning a little allen screw. There are 2 of them as I remember, one being the on/off pressure adjustment, the other being the bypass pressure adjustment, which is the one that needs adjusting.You can trust me on this because I been down this road when I first bought my 4008. I installed it, and it wouldn't completely shut off. I went back to the dealer w/ the problem, and they didn't have the foggiest idea, so they called shurflo, and they right away said to turn the allen screw 1 full turn (don't remember which way) to fix the problem, and they were very correct. I would hope one of the techs here could tell you the exact location of the screw, as I don't remember 3 years ago, but I do remember it is near where the wires connect

Pump hammering after installing accumulator | Good Sam Community

Trackrig
Explorer II
Dec 19, 2016
The two most common accumulator tanks are the littler plastic one and the larger steel one. I installed the larger one in my MH and all has been fine with it. I'll install another larger one in my TT in the spring when it's warm outside again.

With the larger ones you have to set the air pressure in the bladder. In the four years it's been installed, I've had to re-pressure the bladder once. Does the smaller one also need to be pressurized and did you do it?

Bill
ROBERTSUNRUS
Explorer
Dec 19, 2016
:) Hi, if your pump continues to cycle, you might have a small leak somewhere or air in the lines. If you haven't already done this, I would suggest that you install flex hoses to the pump.
obscenic
Explorer
Dec 19, 2016
Trackrig wrote:
The two most common accumulator tanks are the littler plastic one and the larger steel one. I installed the larger one in my MH and all has been fine with it. I'll install another larger one in my TT in the spring when it's warm outside again.

With the larger ones you have to set the air pressure in the bladder. In the four years it's been installed, I've had to re-pressure the bladder once. Does the smaller one also need to be pressurized and did you do it?

Bill

Small plastic. Do you also use a bypass pump? My accumulator was factory pressurized and I checked the pressure and it's good. You can feel it working, you get a nice steady stream when the pump turns off.
Trackrig
Explorer II
Dec 19, 2016
I'm not sure what you mean by a bypass pump? I'm using the Shurflow pump that was already in the MH's water system.

Bill
RJsfishin
Explorer
Dec 19, 2016
If the 4008 pump keeps running slowly after the pressure is up, I can't believe it didn't have the same problem before you installed the bladder tank.
The problem is common on that bypass type pump, and is easily corrected by adjusting it, by turning a little allen screw. There are 2 of them as I remember, one being the on/off pressure adjustment, the other being the bypass pressure adjustment, which is the one that needs adjusting.
You can trust me on this because I been down this road when I first bought my 4008. I installed it, and it wouldn't completely shut off. I went back to the dealer w/ the problem, and they didn't have the foggiest idea, so they called shurflo, and they right away said to turn the allen screw 1 full turn (don't remember which way) to fix the problem, and they were very correct. I would hope one of the techs here could tell you the exact location of the screw, as I don't remember 3 years ago, but I do remember it is near where the wires connect
brulaz
Explorer
Dec 19, 2016
Trackrig wrote:
I'm not sure what you mean by a bypass pump? I'm using the Shurflow pump that was already in the MH's water system.

Bill

The 4008 and others have an internal bypass valve that allows it to maintain pressure without cycling on/off. Sometimes, at certain flow rates, it can be quite noisy.

With ours, it only gets noisy when running cold water. The 6g hot water tank seems to buffer it when pumping hot water. My guess is that the OP would be better off with a bigger pressure tank.
RJsfishin
Explorer
Dec 19, 2016
That type bypass pump doesn't need any bladder tank, let alone a bigger one.

Having said that, mine works great w/ the little bladder tank,.....once I adjuster the bypass correctly.

And having said that, the 4008 is a cheap universal pump that works well for most I guess.
But I have had too many problems w/ mine, like the screws coming loose, until I installed lock buts on 3 of the 4 bolts. Then I had trouble w/ overheating and shutting down when ever using very low water flow. I finally removed the internal thermosistor, and no more problems.

But if I needed a pump, it sure would be a higher quality than the 4008.
Harvard
Explorer
Dec 19, 2016
My pump hammers when it sucks air in water which happens if and when I let the fresh water tank to go dry. The reason for air in the water, AFTER I refill, is because my inlet to the pump has an air trap in the piping.
Hurricaner
Explorer
Dec 19, 2016
Air in the lines. Try opening the faucet all the way after you fill the tanks a let it run for 30 seconds or so.

sam
ScottG
Nomad
Dec 19, 2016
It may be as simple as a line up against a wall or other hard surface someplace. That can make a tremendous racket. A bit of pipe insulation will stop it.