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Old 09-17-2022, 10:09 AM   #1
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Toilets and Black Tanks

Maybe not your typical post on this subject, but.... here it goes.

We have a Thetford toilet (Model 42070) in our Montana and for some time now it's been loosing water. I picked up the gasket and seal kit from my local RV dealership parts shop a few months ago and intended to install the new flapper seal. But, we've been on the road so much, I was a little skeptical about doing this job, maybe run into problems (like reconnecting the water and having leaks), or just getting into something over my head and needing a good parts store. While camping in unfamiliar locations, this is a bit risky for me. So, we decided to just live with the bowl loosing water until we finally returned home.

Well, we finally returned home (yesterday) and first this this morning on my list of update repairs and minor adjustments with the camper was to fix that leaking valve in the bowl of the toilet.

I used this YouTube video as my guide. So, the video was a tremendous help and it was spot on. I'm glad he pointed out the size of each tool neeced. That saved a lot of guess work.

Anyway, I got the toilet apart in the 2 pieces, the base and the bowl.

The first thing that struck me about this specific toilet is the fact it is NOT all porcelain. The actual bowl is, but the base is not. It's plastic, or PVC, or something like that. So, the entire toilet is NOT porcelain like in your home. Well, I suppose that's OK, the thing works. That's all that matters.

Now, the next thing I noticed was all the crud that adhered to the base in the neck that dumps into the black tank.

I took each half of the toilet and set it up in the yard (at home) and proceeded to clean everything before re-installing. Lots of Dawn, Crud Cleaner, and "The Works", and my garden hose with a sprayer. I should have used my pressure washer!

Anyway, the outside cleaned up real nice, but the neck of the base, that black crud on there ... it did not come off. I ended up using a wire brush, and even THAT would not remove all the black crud that seemed to bond with the plastic or PVC or whatever that is. I did the best I could as much as my patients and tolerance allowed and finally said, that's as good as I'm going to get it. Maybe half of it came off, Some white started showing through, but that stuff is just pain tough.

So I was able to get everything back together and the bowl is now holding water! Yahoo! I probably just saved myself a hundred dollars in labor charges if I would have taken to an RV repair shop!

Now, trying deal with the neck of that base made me wonder.... if just the neck is this coated and the stuff is that hardened, what's REALLY going on inside the black tank!
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Old 09-17-2022, 12:02 PM   #2
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You just might have found struvites, minerals that were leached out of the waste and water, coating the lower part of the toilet. I dropped my black tank once because I noticed them in the tank when I was doing valve work. There was a lot of them in the tank. Sort of like big pieces of peanut brittle but thinner and no peanuts of course. If you ever hear a rattle in your dump house work it's way down the hose, it may be small bits of hardened minerals. Was an interesting experience for sure.
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Old 09-17-2022, 01:33 PM   #3
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M.O.C. #22835

You may be onto something there. Actually, there was really no "poo" smell in the lower base at all. It just looked black, and extremely crusted like you said. And yes, some of it did come off, like scales on a fish or something like that. I never thought of mineral build up.

Thanks for your input! This puts me at ease a little bit, maybe it wasn't as "dirty" as I thought.
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Old 09-17-2022, 01:37 PM   #4
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Originally Posted by DutchmenSport View Post
....We have a Thetford toilet (Model 42070) in our Montana and for some time now it's been loosing water....
It isn't really loosing water, it is just relocating it to the black tank. That is the better alternative. Normally Thetford toilets, with good seals, are notorious for filling the bowl due to a leaky fill valve. It doesn't stop when the bowl is full. No fun at 0'dark thirty when you wade into the bathroom (or bedroom carpet). This has the primary driver for many members to change it out to a Dometic 310 or 320.
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Old 09-17-2022, 02:13 PM   #5
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I am glad I put in a new Dometic a few years ago. It takes about 5 minutes and no tools to change the rubber seal in the bottom of the bowl.

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Old 09-18-2022, 07:21 AM   #6
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I have a brand new Dometic in the box ready to replace the Thetford. Water was gathering where the base and floor meet. I don’t know where the leak is but I never trusted it anyway so good reason to swap it out.
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Old 09-18-2022, 08:54 AM   #7
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I actually had Tetford send me the parts to do that repair under warranty. Several weeks later the bowl still leaked. Went with Dometic and no problems. Both Monty's we currently own had to have a Dometic installed before we even took it off the dealers lot.
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Old 09-22-2022, 09:11 AM   #8
Bruce in DFW
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Got tired of fixing my Thetford Aqua Magic II and just replaced it with a Dometic 320. I must have repaired my Thetford at least 3-4 times - replacing the gasket, valve and the part that swivels to hold or release the water. The Dometic has been working well for the past few months - but the 320 is the elongated bowl - which means that you sometimes have to use extra water to get any TP off the front portion of the bowl. Dometic needs to create more water flow on the front portion of the bowl to resolve that issue. The 310 is the round bowl - which, most likely, doesn't have the same issue as the 320 - but I think I would buy the 320 again over the smaller, round 310.
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