leaking black tank

[jackparretta]

I have a 2018 333mks . I had it since new and never filled the black tank up because we just do weekend trips only then we add water then dump. This week we filled black tank up to full level to where you can see water coming up in toilet ( we used water hose down the toilet ) we notice water coming out over the bottom of the 5th wheel it stop when it to 3/4 to the full level , then i did it again and sme thing happened. I removed bottom cover to check were its coming from fill it up and its leaking from top of tank and running down the side of tank has anybody had this problem , just wondering when they drill vent or toilet pipe off center or something . it not a slow drip it pours out just as fast as i fill it .

[JRTJH]

You may have a "unglued" vent stack. Some are glued in place, some are pressure fit. A pressure fitted vent stack can leak under pressure. If it's not the vent stack leaking, you likely have a split/rupture along the top of your black tank. They are "roto-cast" so there's no "seams on the tank" as they are all "one piece construction".

There are some "repair products for RV holding tanks" but successful repairs run about 50/50 from what I conclude from people who have tried to repair their tank.

For me, if I'm going to all the trouble of removing the underbelly material, removing the black tank to "get to the repair area", I'm going to just replace the tank with a new one rather than "risk" having to do it all over again if the repair job doesn't work and hold properly..... YMMV

ADDED: You didn't mention any "gawful" smells coming from the underbelly, so are you sure it's the black tank leaking ???

[Ken / Claudia]

I am not sure it would matter, but when I top off the black tank. I use a 1 gal bottle just for that purpose. Fill the bowl and open toilet valve. For 2 reasons, no over filling and no high water pressure filling tank.

[Scttw]

Mine was overfilled accidentally year 1 before I realized the sink flows into the black as well so at least it was clean. This happened as I was running the water to drain anti-freeze. I cut an access hole in the belly to drain it.

The water did NOT come up the toilet, it overflowed prior so I thought maybe this was a way to NOT flood the trailer.

In any event, if you drain when it gurgles it will be full but NOT completely full and you wont have to worry again.

[jackparretta]

It's is the black tank , leaks even when i fill by holding flush pedel down to fill. thanks for all the reply I'm having dealer repair it under forever warranty

[Scttw]

Ohhhhh, it leaks even when flushing ....... understood.

[Javi]

Just a note... the 333MKS has about 4 feet of 3" pipe running up to the toilet from the top of the tank. Probably shouldn't fill it up until you can see the water in the toilet...
Yep... that black pipe in the basement with the 45 degree elbows is what you're looking down into from the toilet...
Waaaaay over filling the tank.

[chuckster57]

Originally Posted by jackparretta

It's is the black tank , leaks even when i fill by holding flush pedel down to fill. thanks for all the reply I'm having dealer repair it under forever warranty

I would make sure the “forever warranty” is going to cover it before I authorize any work. At $150.00- $175.00/hr. It can get very costly.

[falcondan95705]

I have owned 4 other 5th wheels. Id fill the black tank to the toilet then empty them. On our New Montana, when i tried to fill the black tank the water never made it to the toilet. This black tank uses a two piece unit with the top GLUED TO THE LOWER TANK!!! Black water was leaking out the belly.. JUNK!!!!. To get the under belly off the factory uses nails that go through the frame, FUN TO REMOVE THEM!. USE self tapping screws and washers when putting back together. After getting the belly off and washing the real fun starts. First, remove the wall in the storage area to gain access to the black tank pipes. Use a sawzall and cut the plpes, use rubber boots and hose clamps to put back. Remove black tank flush hose and slide valve. Back under cut the wires for level and heat blanket. Renove two bolts that hold the rail to the tank. Pound the rail to slide away from tank. Tank will now come down. Clean the thank and use mesh and abs to seal separation.. test tank and reinstall.

[jackparretta]

update black tank split on top of tank at the seam . forever warranty paid for relacement tank and labor

[Javi]

Originally Posted by jackparretta

update black tank split on top of tank at the seam . forever warranty paid for relacement tank and labor

Good deal 👌

[falcondan95705]

Where does one get a forever plan? Thanks

[jackparretta]

my dealership offers it when we bought our 5th wheel. You just bring it in once a year for inspection. 150 dollars for inspection

[falcondan95705]

Thank you. I'll check mine
.