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Old 05-22-2023, 12:48 PM   #1
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Need advice on unusual black tank situation

Hello out there,
I have a strange black tank configuration that is causing problems. I'm hoping someone out there has this same set up and can give me some advice.

The black tank has an upper level that drops down to the lower level, where the drain is. The problem that the toilet dumps on to the upper level, so all of the "product" lands right there while all the water just bypasses and runs down to the lower level. We use plenty of water but whenever a 2 happens it stays there and things piles up, the water doesn't really help because its down in the lower level. I have to resort to getting the hose out and blasting it apart. My last trailer and every other RV I've had all had a contiguous bottom, where the water could build and prevent this from happening.

Here are some images, hoping to convey what is happening. Anyone have a tank like this and know a trick? This is on a 2022 Winnebago Voyage 3033BH.

Thanks for your time!
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Old 05-22-2023, 01:17 PM   #2
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When going #2 fill the toilet bowl FULL before flushing then continue to flush for couple seconds

That is a very POOR designed black waste tank
Unusual -----typically toilet end is shallow but SLOPES towards opposite end when outlet is

Maybe install a Sprayer on toilet.

Which brand/model is your toilet??
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Old 05-22-2023, 01:18 PM   #3
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Looks like you have some access. I'd consider installing a black tank flush in the end of the upper level pointed in the "drop zone" to flush towards the opposite end of the tank.

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Old 05-22-2023, 03:15 PM   #4
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Very poor design for a black tank, maybe fine for gray.

I would install a hand sprayer, or a macerator toilet....the alternative is replacing the tank with something suitable. But your framing may not allow that.
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Old 05-22-2023, 03:40 PM   #5
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Old 05-22-2023, 04:12 PM   #6
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Ohhh… You’re in a HEAP of trouble…
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Old 05-22-2023, 05:30 PM   #7
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We had the IDENTICAL tank in a 32' Fleetwood Terra. The toilet drop was on the outside of the frame rail and the bulk of the tank was on the inside of the frame rail.

It clogged constantly. I complained to Fleetwood and they played stupid, but after we dumped the coach for that, brakes and some other issues, there was a recall it for the tank issue.

Here's some of the things I did to improve it. First, I put a water line shut off at the back of the toilet so I could open the bowl without the water running. Second, there is a hose attached to the bottom of the toilet that drops into the tank. You need to make that hose as short as possible so it's not deep into the tank. Cut it so it just slides into the fitting.

Lastly, on mine i was able to swap out the smaller RV drain mount for a larger residential size mount, making the hole bigger.

On ours, with the ability to shut the water off and open the bowl, we could at least use something to clear the buildup. If you only use the water pump and don't hook to shore water, you don't need the switch.
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Old 05-22-2023, 05:57 PM   #8
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If I was going to re-engineer this I would try to add a sweep or at least a 45 or 22 1/2 with a extension to the under side of the toilet flange to get everything going in the correct direction. Hopefully it could then clear the ledge and not be a problem. It is a poor design in my opinion. Hope you work something out that fixes the issue.
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Old 05-23-2023, 04:03 AM   #9
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Wow, that's just about identical to the toilets we saw in Russia in the mid-80s. First the business drops to a landing. Then hopefully goes away when the toilet is flushed.
I thought that only the Russians could design something that dumb.
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Old 05-23-2023, 07:27 AM   #10
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Please reply back to this thread once you resolve it. It will be educational.
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Old 05-23-2023, 04:06 PM   #11
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A black tank rinse sprayer installed on the top level near the "landing zone" would at least give a way to wash down the top shelf.
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Old 05-24-2023, 12:15 AM   #12
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The other suggestions notwithstanding, your best bet is probably to get a macerator toilet and write this problem into history. No solid piles if no solids.
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Old 05-24-2023, 06:18 AM   #13
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Well that's a shi**y design. All the "solutions" require wasting a lot of water. It might not be a problem if you never boondock. I do a lot of boondocking and am always conserving water and would hate this setup.
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Old 05-24-2023, 04:18 PM   #14
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Hi all, thanks for all the responses.

Old-Biscuit: the fill before flush is good advice and what I'm trying to implement. The Mrs is not accepting that our new much higher quality trailer does not perform as well as the previous one in this department. The toilet is a Dometic single pedal version, looks most similar to the 310 on Dometic's site, I haven't found a model number. I have noticed that the bowl does not like to hold water for long, I think the rubber seal might be a little dried out. I'll try some Oring lube and see if that improves the ability to fill. I also get complaints from the family about how hard it is to push halfway on the pedal to fill the bowl, not a problem for me.

Dutch: I put a valve on the supply to the toilet in my last trailer for that very reason, so I can see what's down there. I'll install one here as well. I'll check the depth of the tube as you suggested.

Others: Since I do seem to have access I'm thinking about how I can add a tank flush to that end. There is one already on the opposite side somewhere. I want to try to plumb the new one to a valve in the bathroom so I can activate it from the inside, I'm thinking of hiding the valve under the sink, easy to reach from the seat. I'll let you know what I come up with. If you have any more thoughts let me know!

I sat on hold with Winnebago for 45 minutes before giving up, but I want to see what they have to say, maybe I'll get lucky and there was a recall like Dutch suggested.

Changing out the tank is an option that I am considering, I'm looking in to others out there, but I hope I don't have to go that route.

Thanks for all the ideas.
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