New Dometic 310 Toilet Flow

[rjreiffer]

Hello all,

I just purchased a Dometic 310 porcelain toilet to replace our old Thetford Galaxy toilet (gave us the “comfort” height and elongated bowl).

Now the install went fine (even dealt with the changing of the bolt pattern from 11 and 5 to 9 and 3) but when I hooked it up everything works but the flow was very low. The toilet fills nicely and flushes but the flush stream is very weak with the holes near the back pushing out water but the front ones, nothing. So a couple of things. My pump is rated for 2.8GPM and I measured the output by filling a gallon jug and measuring the time to fill with a stop watch. It ends up being about 37 seconds to fill the jug (now I tried it by using the output of the line to toilet bowl - unrestricted but no back pressure from the pump - and from the kitchen sink - restricted by the faucet but with back pressure from the pump and the results were about the same).

Now based upon this it is approximately 1.6GPM flow (way below the 2.8 on the pump). The minimum flow for the toilet is rated at 2.0GPM with a recommended 3.0-5.0GPM. I did verify that there was nothing restricting the intake to the valve. I did contact Dometic and they are shipping me a new valve and hose just to be safe. I also have ordered a new pump (SureFlo 3.5GPM, 45 PSI) as well just to be safe as we are heading out next weekend.

So here are a couple of questions:

1. Do pumps lose their capabilities over time? Dropping from the rated 2.8GPM to 1.6GPM?
2. Of the two, which would you suspect more? Pump or valve?

Thanks all!

[rjreiffer]

Ok, anyone have experience with an older pump?

[Kahoona]

Hook it up to city water and try it. That should give you the answer. .


Do you spend time off the grid or in places without a full hookup? If you put in a high capacity pump you will also need to put flow limiters on all of your faucets and shower or you will fill that grey tank in no time.

[Elwood58]

Originally Posted by Kahoona

Hook it up to city water and try it. That should give you the answer. .

My thoughts exactly. If OK on City Water then Water Pump issue. If not OK on City Water then toilet valve issues.

[rjreiffer]

Originally Posted by Kahoona

Hook it up to city water and try it. That should give you the answer. .


Do you spend time off the grid or in places without a full hookup? If you put in a high capacity pump you will also need to put flow limiters on all of your faucets and shower or you will fill that grey tank in no time.

I will test it. I do nothing off grid but some without full hookup. I will keep your tips in mind! I suspect it is the pump since it is running below the minimum required by the toilet. Thanks

[Gary RVRoamer]

The water pump rating is direct at the pump outlet, with zero back-pressure. 1.6 gpm inside the RV is about what you typically get with a 2.8 gpm pump. The 3.5 should be better, but 4 or 5 would have been better yet. Note that the bigger rated pump needs more electric power - if the wiring can't supply enough to meet the pump demand, the flow will still be low.


City water pressure is usually more consistent but it can vary a lot by campground or even homes. If the city supply is 50+ psi and you use a 5/8 or 3/4" hose, it should be able to maintain 2.0 or more gpm.

[leadman]

Water pump can lose flow as the diaphragm gets old.

[rjreiffer]

Update:

Tested toilet with a direct hookup to the house, finally a good flush!

Replaced the pump with a 3.5gpm shurflo and now the toilet does much better!

Probably could have gone with a 4.5 or 5.0 but just didn’t want to spend that much ! (Me being cheap )