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Old 06-13-2018, 06:38 AM   #1
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M.O.C. #19731
Dometic 320 Toilet - Will it Fit All Montanas?

So I am plumbing challenged, so before I take the advice offered here about replacing my Thetford Toilet with a Dometic 320, I wanted to ask this question after reading reviews on Amazon. Sounds like the advice here is to replace your Thetford before you regret it?

1. I have a 2018 3721RL and wanted to find out if this toilet will fit? Our toilet is located against a curved back wall.

2. Can a plumbing impaired guy like me install it? In other words, can, say a 8th grader install it?

Thanks in advance!
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Old 06-13-2018, 06:43 AM   #2
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Yes. You will need to take some measurements. On our 2010, had to adjust a closet door in the bathroom so it would open and close. Easy install. YouTube videos available.
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Old 06-13-2018, 06:59 AM   #3
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M.O.C. #15731
I just replaced mine and you need 11" from the center of the floor flange to the wall for the 320. It was easy to do the only issue is i changed the fresh water hook because the placement was different. But easy to do.
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Old 06-13-2018, 08:41 AM   #4
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My back wall is curved as well and the only thing I had to do was figure out how I wanted to handle the difference in water inlet as noted above. I made a pex based adapter to handle the issue, but flexible braided hoses exist to do it as well.
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Old 06-13-2018, 09:08 AM   #5
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I would change it before you have a problem with. Are's leaked the first time out from the air gap valve on the back of the toilet put in the 320 and never looked back! it's ease to do i'v done it in 3 other SOB's you can watch some of the vid'd on how to do it.
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Old 06-13-2018, 09:13 AM   #6
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In our 2010 we had to cut a closet door and had to use the smaller bowl one, I believe it's 310 in order to get the door to close. So be sure and measure.
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Old 07-14-2018, 04:34 PM   #7
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Just curious, but I have a 3000RK 2010 Montana. Has anyone put the Dometic 320 in their rig. Measured the distance from bolts to wall and I think it was about 10 1/2 inches. Everyone says you need 11 to 12" to fit so it doesn't hit wall I guess. Have had the Thetford since 2010 and no leaks yet, but wonder if I am just lucky and it will cause major problem in near future.
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Old 07-14-2018, 10:23 PM   #8
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Search the net for an installation manual for the 320. I did it this spring and the manual has ALL the dimensions you need - width, depth, etc - with pictures/diagrams.
Others have mentioned rotating the flange in the floor a little to gain clearance for doors, etcs.
If you are using PEX piping, be sure to use shark bite connectors. Everyone including me raves about them. SOooo easy to use. I even spent the extra $3 or so for the removal tool!!! Never know when you may want to change things later on.

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Old 07-15-2018, 04:51 PM   #9
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It went into my 2015 3100rl with no problems.
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