Dometic toilet problems

[ORV1980]

We are having two issues with the Dometic 320 toilet in the half bath.

1. When I push the pedal to flush it does what it should. When I release the pedal I get a loud water hammer sound. Do I need to replace the vacuum breaker? I already had to replace the vacuum breaker on the Thetford toilet in the front bathroom.

2. After releasing the pedal the water runs in the toilet for several seconds, sometimes longer then others. It has not overflowed yet, but would rather not have that happen. Do I need to replace the flush valve?

I am having trouble finding a parts diagram with part numbers, I have even gone to the Dometic web site.

Also, yes I have checked the water pressure at the supply. It is 40 psi.

 

[danemayer]

Here's a link to the water valve for the 320, pn 385311641. Here's a link to the manual.

As I understand it, the purpose of the vacuum breaker is to prevent water from a full bowl from contaminating your water supply lines if there's negative pressure on the line while the bowl is full.

So I don't think your noise is from the vacuum breaker. It's probably from the water valve.

 

[ORV1980]

Here's a link to the water valve for the 320, pn 385311641. Here's a link to the manual.

As I understand it, the purpose of the vacuum breaker is to prevent water from a full bowl from contaminating your water supply lines if there's negative pressure on the line while the bowl is full.

So I don't think your noise is from the vacuum breaker. It's probably from the water valve.

I thought the vacuum breaker acted like an anti-hammer valve also, but I am no where near an expert when it comes to plumbing.
I will replace the water valve and see what that does.
Thanks for the advice and links Dan.

Sherman

 

[rxbristol]

I assume you have the Dometic 310 or 320...yes, the water will "percolate" some after the flush. I've yet to figure out why it sometimes does it more than others. I had the same worry you do about it overflowing, but I installed a shut-off valve at the toilet inlet and it will still flows water out of the bowl jets even if the water is shut off. I've had the toilet for almost three years (full-timing) and it still works great.

 

[Roller4tan]

Hard water deposits wreak havoc with rv plumbing. When the toilet foot lever gets stiff and not function properly, it's usually time to take the water valve apart, clean and apply plumbers grease to the moving assemblies.

 

[ORV1980]

Hard water deposits wreak havoc with rv plumbing. When the toilet foot lever gets stiff and not function properly, it's usually time to take the water valve apart, clean and apply plumbers grease to the moving assemblies.

We have had the RV for less than a month so I don't think it is hard water deposits, but it could be crud in the lines from when the unit was built. I am sure they are not that careful at the factory when they assemble the plumbing. Derbies from cutting the pipes could get left behind. But dissembling and cleaning the valve would solve that problem.

- - - Updated - - -

I assume you have the Dometic 310 or 320...yes, the water will "percolate" some after the flush. I've yet to figure out why it sometimes does it more than others. I had the same worry you do about it overflowing, but I installed a shut-off valve at the toilet inlet and it will still flows water out of the bowl jets even if the water is shut off. I've had the toilet for almost three years (full-timing) and it still works great.

Were you able to get a shut off valve that you could splice right into the PEX?

 

[mlpeloquin]

We have had the RV for less than a month so I don't think it is hard water deposits, but it could be crud in the lines from when the unit was built. I am sure they are not that careful at the factory when they assemble the plumbing. Derbies from cutting the pipes could get left behind. But dissembling and cleaning the valve would solve that problem.

- - - Updated - - -

Were you able to get a shut off valve that you could splice right into the PEX?

He maybe referring to Shark Bite shut of valve. They push on and seal well. You must be able to cut the PEX cleanly and a almost perfect 90 degrees. Easy if you have the proper tools. https://www.homedepot.com/s/shark%20bite%20shut%20off%20valve?NCNI-5

 

[rxbristol]

Were you able to get a shut off valve that you could splice right into the PEX?

I used one of these shutoff valves (Link), along with a couple of 90 degree elbows to make everything fit. I like the press fit sharkbites because they swivel.

 

[ORV1980]

I put in a new water valve but still have the water hammer. I had to put the old valve back in because the new one I bought online leaked every time it was actuated. It looks like the seal at the end where the push button is came apart. It is on its way back.

I emailed Dometic about the water dribbling in the bowl and the water hammer and this was their reply.

This toilet will trickle water up to 20 minutes after flushing the toilet. It is residual water draining from the rim area. This is normal and it mentions this in the Owner's Manual. The loud noise is water hammer. I suggest installing a water hammer arrester within 6 inches of the water valve. Water hammer arresters can be purchased at a local hardware store.

So i guess i need to make a trip to the hardware store for a hammer-arrester and some shark bite fittings.

Thanks all,
Sherman

 

[Garypowell]

Another thing you can do is trace your lines while flushing to see where the noise is coming from. I believe the hammer part is from a pipe that is hitting something.

Could be another pipe or the structure. Did that on mine and found the culprit where water lines crossed and put some insulation between them to solve the problem.

Also remounted Ted the water pump to make it more quiet.

I do believe too that a little water hammer is normal....these are not residential systems.

 

[ORV1980]

Another thing you can do is trace your lines while flushing to see where the noise is coming from. I believe the hammer part is from a pipe that is hitting something.

Could be another pipe or the structure. Did that on mine and found the culprit where water lines crossed and put some insulation between them to solve the problem.

Also remounted Ted the water pump to make it more quiet.

I do believe too that a little water hammer is normal....these are not residential systems.

Gary,
I had forgotten that I did have a little water hammer on my last trailer, but only when i was using the pump. I was able to quiet it down by adding some pipe insulation.

On this trailer the noise is the same whether i am using the pump or on city water, and only when we use the rear toilet.
I will crawl into the basement and see what i can find. I am sure there are a few loose pipes. I would think that PEX pipes are more apt to move and cause noise also.

I was curious, do you name all the equipment in your trailer or just the water pump?
>Also remounted Ted the water pump to make it more quiet.

Sorry, but I laughed when i first read that. Auto spell check is out to get us.
Thanks,
Sherman

 

[Garypowell]

I usually reread everything...and did this post....but proved once again I am human!

we have named a few things....but not the water pump

let us know what you find.