Hammering water pump

[bcmorr]

Since I bought my new trailer the water pump works, but it hammers between cycles. In my old trailer it would pump then go silent a couple seconds then pump again. This one never goes silent. Dealer said nothing was wrong with it. I installed a silencing kit and it's usable now but still hammers between cycles. Any ideas I could try? Would a new pump be worth a try?

[Camping Couple]

It sounds like you may have a small leak in a water line or one of your faucets is slightly dripping. The reason it is hammering or most likely cycling on for a short burst is to build up pressure in the water lines. Check all your faucets, outdoor shower if you have one and make sure they are all closed. Also check all your fittings with a bright flashlight for dripping.

[NVGun40]

What trailer do you have?
To my knowledge and someone correct me if I am wrong. Most, if not all trailer water pumps are on demand. Meaning they will pump and pressurize the system until a certain back pressure is detected by the pump, then stop pumping. Once in a while there will be a pressure bleed off and they will cycle periodically to return to full pressure.
Usually this indicates a warn seal of some sort in the pump or worse yet a leak somewhere in the system.
What exactly is "hammering between cycles"? If you are referring to the occasional cycle to return the system to full pressure. Then I would say that is normal. I would still check for leaks.
On our new TT, the pump runs to pressurize the system and then stops. we have sat in it for almost two hours and it does not cycle/run again. Indicating the systems maintains full pressure and there are no leaks. Even still, we try to make a habit to shut the pump off when not actually running water.

[rryman]

I think I had the same problem you are describing. When I de-winterized it last week and started the pump, it would do the "hammering" noise while it was running. Turns out one water line under the floor in the basement was close to the underside of the floor, and the pump pulsations were making it vibrate against the plywood, and it basically acted like a speaker and sounded awful. Had another line under the sink in the bathroom doing the same thing. A little pipe insulation on both stopped the noise.
After the pump builds up pressure and stops, it should not run again unless you open a faucet or flush the toilet. If it is coming back on with all valves closed, I'd start looking for a leak.

[bcmorr]

It only does it when I turn on a faucet. It does not run at all when it shouldn't be I don't suspect any leaks. If I open a faucet wide open it hums along nicely, but if I close the faucet slightly off of wide open, it begins to hammer hard. The pump shakes which in turn makes pipes shake. I try to run faucets full boar to avoid it, wastes alot of water that way. My old trailers pump never acted this way is why I suspect something wrong. My trailers a 2014 33.5rets

[rryman]

I suspect you have the same problem I had. Same thing, wide open, no noise except the hum of the pump, but if you turn it on slowly, it hammers. My unit is a 2014 also, and has Pex plastic piping. I couldn't tolerate the noise, so I tracked it down and insulated them from what they were vibrating on. I think it may also eventually wear into the pipe if let go long enough. Part of the reason for the hammering is no expansion tank anywhere in the system, except for the small space in the top of the water heater water heater. (just found that out the other day reading the Atwood manual). When I found the one pipe in the bathroom vanity that was vibrating against the shelf, I thought I had fixed it. But the big noise was coming from underneath. Had to remove a false wall to get to it, but I eventually found it. I suppose they can't catch everything at the factory.
Good luck and be sure to let us know what you find.

[huronwoods]

As mentioned in the previous post, there is no expansion tank in the typical RV water system, except in some high-end models. The solution is to install a tank like this one.
It can be installed almost anywhere you can find room, by putting a tee in the pressure line after the pump outlet. I installed one in our Pinnacle, and we can run at least a gallon of water before the pump will come on. When the pump does start, it runs for longer to repressurize the tank.

[fmichaels]

sounds like something an accumulator would fix.

[Camping Couple]

Originally Posted by fmichaels

sounds like something an accumulator would fix.

If you read the manual for your water pump, it may say an accumulator is not needed. Something to check out. Our manual says not to use an accumulator.

[arkhillbilly]

I would tighten all water fittings. The word is "pressure loss", and even a slight air or water loss will cause the pump to cycle. Pay attention to the in-line filter just before the pump. You probably will not find a great deal of water.

[3'senough]

I am leaning with the leak, air or valve issue first. Usually once the system charges the pump shuts off. If that is not happening something is either wrong with the pressure switch or you have a leak somewhere. Is your winterization valve open? This could be introducing air to the system when on and won't leak since it is behind the pump.

The accumulator is good for short cycling elimination and helping the pump maintain pressure with some breaks. I have a 2 gallon on mine and it will run for about 10 seconds wide open before kicking on. This too reduces "hammering" which is a short abrupt stoping of the water flow.

Pipe insulation is a great cheap tool to insulate pex from hard structures and reduce noise as well.

[rryman]

……………..Our manual says not to use an accumulator……
====
That's interesting. I was just reading the Atwood water heater instructions the other day, (imagine that, a man reading instructions!) and it says that the Atwood water heater has an intentional air gap built into the top of the water heater.(I did not know that) But, over time the air will be absorbed into the water, and explains how to drain enough water to get the air gap back.
It goes on to say that a dripping pressure relief valve is not an indication that it is bad.
Lastly, it says that installing an accumulator may help.
Probably, when there is no more air in the water system, hydrostatic pressure may cause the pressure relief to vent. Adding an accumulator, which has a rubber bag separating the air from the water, may solve several problems: dripping relief valve, hammering sounds, and excessive pump cycling.

[Crabman]

There is a small accumulator tank that is made for the Shurflo pumps. I installed this one along with my sound reducing mod as shown to cut down on the short cycling and pump noise. Others have installed the previously mentioned 2 gallon tank with good results as it has more volume, if you have the room for it.

[rryman]

Wow, nice installation Crabman. I sure don't have that kind of room where my pump is located.

[Crabman]

Originally Posted by rryman

Wow, nice installation Crabman. I sure don't have that kind of room where my pump is located.

Thanks. This is what it looked like before the mod. It was mounted to the wall that separates the kitchen from the front bedroom under the kitchen sink. It was VERY LOUD before this mod, hammered like a jackhammer..

[norty1]

Does the Accumulator have to be tied directly into the pump or can it be somewhere else?

[rryman]

I would think anywhere in the cold water line would work. I have two in my garage that is located some distance from where the pressure switch is and they seem to work fine. If I install one, it's going to have to be on the opposite end of the trailer from where the pump is.

[3'senough]

Originally Posted by norty1

Does the Accumulator have to be tied directly into the pump or can it be somewhere else?

Anywhere in the system. Around the pump sometimes is easiest with connections due to there being threads vs pex.

[Paintinfool3]

Well mine was horrible echoing through the camper and the installation of the silencer kit and insulating the pex lines where the contacted the wall or floor with standard pipe insulation has almost completely silenced it.

[Bobalink]

silencing kits are available at RV supplies, small air tank that attaches to pump, you put about 25 lbs of air in it stops the hammering about 30$