Replacing Thetford pot with Dometic 311

[Pahaska]

I have hated the Thetford toilet from the time I bought the AI. Even so, I didn't know just how flimsy it was until I removed it. Even my first Airstream, a 22' International, had a ceramic toilet and I upgraded both of my larger subsequent Airstream trailers to ceramic toilets. The trailer upgrades were a lot easier than the AI.

The floor flange for the Thetford is about 3/4" high and is not compatible with the Dometic which requires a flat plate. It is a pain to remove the Thetford adapter which is covered in sealant. I solved this problem leaving the Thetford flange and buying a Dometic adapter that goes around the Thetford plate to provide a flat mounting area.

To make the installation easier, I modified the bathroom extension so that it would swing completely open. I will relocate some of the catches so that I can easily open the extension completely in the future to clean the area behind the toilet.

The Dometic seat is larger and the seat just barely hits the closed extension when it is raised. I'll put a bit of padding on the extension where the seat hits. The seat is vertical when it hits and the toilet can be used without opening the extension.

The hardest part of the installation was the water feed line. The Thetford is plumbed with PEX and the water enters the two toilets in very different places. I temporarily removed the gray cover behind the CS second row seat and used my Dremel with a grinding wheel to cut the PEX rings. I salvaged all of the elbows and the water shutoff valve. I reinstalled the parts using 1/2" flexible tubing with clamps. I used a heat gun to soften the tubing to push the bayonet ends in. To connect the flexible tubing to the PEX stub, I used a push-on Shark-Bite brass connector. The push-on feature made it a lot easier to connect in the limited space behind the second row CS chair. The second photo shows the connection to the PEX.

[wachuko]

Thank you for sharing.

[cwf]

Excellent! Just rebuilt our Thetford valve.. The throne is only 3 years old.. and plastic.. really an awful design...but had to make quick decision 3 years ago and this was only available.. upgrading/rerouting stuff is always redesigning... and improving a poor execution... Altitude, airspeed and attitude..

[Pahaska]

Another view of the Dometic 311 on top of the Dometic adapter. The adapter provides a level mounting surface.

I haven't installed the "water saver" sprayer yet. With the AI quite cold soaked, the sprayer hose is very stiff. I'll wait until it is warmer to pick a spot for the bracket when I can see how the relaxed hose will lay.