Replacing Thetford 42072 Toilet with Dometic 320

MCTalley

Well-known member
I have, in every rig I've owned (three Big Countrys). The 320 is a bit deeper from the center to the back. If your Thetford is not at least a couple inches from the wall, you will have trouble with fitment. Also, the Thetford and the 320 have water hookups in slightly different places - enough different that you'll have to get out the Pex tools, some fittings and several inches of 1/2 inch pex to make up the difference. It's a great time to plumb in a shutoff valve, too.
 

porthole

Retired
Aside from what Malcom mentioned above with installations issues - there is a reason why he has installed it on 3 different RV's. As far as RV go, it is probably the best toilet out there before moving up to the higher end macerator style toilets.


And while you are plumbing in a shutoff valve, tee in a kitchen sink style sink sprayer.


Dometic 320 install

Toilet - bathroom sprayer add on
 

RoadJunkie

Well-known member
It looks like the required dimension from the center of the rough in opening to the wall on the Thetford is 1 1/2” less than that of the Dometic. I don’t have that much room. Thinking I’m stuck with the Thetford and not real confident since the foot pedal fell off. I put it back in position, but the design is such that each reposition make the pivot connection shaft weaker.
 

MCTalley

Well-known member
That's why I replaced mine in my first rig (the foot pedal design).

We had a tight fit in our second rig - a front bath 3950 Big Country. The FB models have the toilets very close to the walls due to the routing of the sewage line (between your pass-through storage and the front storage compartment). The corresponding Bighorn (3870, 3871 and 3875) and Landmark (Newport and probably Arlington) models have the same issue, from what I remember.
 

RoadJunkie

Well-known member
As a non-royal, I can only dream of ascending to the stability, comfort and artful aesthetics of the Dometic—comfort height—model 320... Bone color, of course. I may never witness, read stare, at the amazingly hypnotic, yet efficient motion of the swirling streams of water as they precisely perform their duties. I must get over what I cannot have.
 

farside291

Well-known member
There are other choices besides the 320 that may have the desired wall to hole spacing you need. What about the Aqua-Magic Residence RV Toilet, it has the 9.5 inch wall spacing and it comes in high profile or you really want to feel like a king check this one out, Thetford 38264 RV Toilet. Most of the other residence styles with the elongated bowl have the 11 - 11.11 inch wall to hole spacing.

Just a thought, what about a round bowl Dometic 310? It has a 10 inch wall to hole spacing, its actually very similar to the 320 and you can get that magic, hypnotizing bowl swirl when you flush:)
 

farside291

Well-known member
I have, in every rig I've owned (three Big Countrys). The 320 is a bit deeper from the center to the back. If your Thetford is not at least a couple inches from the wall, you will have trouble with fitment. Also, the Thetford and the 320 have water hookups in slightly different places - enough different that you'll have to get out the Pex tools, some fittings and several inches of 1/2 inch pex to make up the difference. It's a great time to plumb in a shutoff valve, too.


MCTalley, when you changed your upstairs toilet in your old 3950, do you remember the hole to wall spacing? I ask because the Dometic 310 has a 10 inch spacing instead of the 11.5 like the 320.
 

SLO

Well-known member
I put the 320 in my BH 3685. The toilet drain pipe was conveniently located behind the basement wall. A 3” ABS 22 1/2 fitting and a 3” ABS 22 1/2 street fitting offset the drain pipe just the right amount to accommodate the 320. Added a Kohler slow close seat and life is good.


Sent from my iPad using Tapatalk
 

Gaffer

Well-known member
You need 11 inched from the wall to the center of the flange for the 320. A 310 needs less room.
 

RoadJunkie

Well-known member
Just a thought, what about a round bowl Dometic 310? It has a 10 inch wall to hole spacing, its actually very similar to the 320 and you can get that magic, hypnotizing bowl swirl when you flush:)

I had the 310 in my previous BH 3670 and it preformed well. Maybe I will go in that direction. I will also look at the suggested Thetford.

- - - Updated - - -

You need 11 inched from the wall to the center of the flange for the 320. A 310 needs less room.

Hey, P.J. I see that you guys were in slot N15 again this year. We were in LHC for a few days last week. we went past your rig but no sign of life so he scooted on. sorry we missed you and Carrol.
 

MCTalley

Well-known member
MCTalley, when you changed your upstairs toilet in your old 3950, do you remember the hole to wall spacing? I ask because the Dometic 310 has a 10 inch spacing instead of the 11.5 like the 320.

It wasn't ideal, but I wedged a 320 in our upstairs bathroom on the 3950. Since it sits at an angle, I angled it a bit less, but the back corner of the 320 was pushing into the wall pretty good. Also, with the shallower angle (it pointed more towards the front than to the side), I had to be careful not to hit the corner of the sink cabinet with my knee.

Sounds like a 310, if it has about an inch less depth in the back, would fit pretty well. The 320 fit great in the downstairs half bath.
 

mlpeloquin

Well-known member
I replaced mine with a 310. Still about 3/4" deeper, but fit. I adjusted the PEX line using a heat gun. Watched this process on This Old House. Worked well to slightly "S" curve the existing line so that there isn't any tension on the fitting.
 
Top