Fun with black water tanks

[sberry1]

At the end of last season, I made the unfortunate error of turning off the wrong water hose after flushing my black tank. I had closed the tank off and later heard a loud bang.

The tank no longer holds any liquid. Nothing comes through the drainpipe if I add water, it all comes out the bottom. I haven't removed the plastic cover on the bottom yet. It was the end of September and I had two weeks left before closure.

If anyone else has experienced this, what should I expect to find once I cut away the under-cover? I've been told a crack that can be sealed. Should I expect to need to replace the entire tank? Any insight into this would be appreciated.

[norty1]

If you wait until winter is over, you may not have much of a camping season next year. Until you can get it checked out, there is no way to know.

From your description, it sounds like a pretty big split. Personally, I would not feel good with a patch.

[GHen]

I agree, depending on the crack, I would replace the tank. A patch on the black tank is the last thing you want to fail while at a summer parking spot, what a mess that would be….

[Flashdman11]

you will find a stinky mess for one. I also agree to replace the tank, you don't want to be under there every year patching it.

[Dkastner]

We had a small leak in our black tank in a previous RV. Since it was still under warranty, we took it to the dealer for repair. The dealer was told by the manufacturer to patch the leak, even though they were not certain what would be an effective patching material/method.

Long story short, the replaced the tank after a few weeks of a failed patch.

Don't forget - a leak in the black tank means sewage is dropping out on the grass, driveway or parking lot.

[Yooper906]

To me it doesn't seem like you could have over pressurized the tank with the flush valve, isn't here a vent or "stink pipe" going to through the roof with a weather cap on it?
Probably I'm reading this all wrong.

[norty1]

Originally Posted by Yooper906

To me it doesn't seem like you could have over pressurized the tank with the flush valve, isn't here a vent or "stink pipe" going to through the roof with a weather cap on it?
Probably I'm reading this all wrong.

It's not like the movie RV at all. I have seen 2 black tanks overflow and both came out of the toilet first. Maybe with a high pressure source the results may be different?

[spoon059]

Originally Posted by Yooper906

To me it doesn't seem like you could have over pressurized the tank with the flush valve, isn't here a vent or "stink pipe" going to through the roof with a weather cap on it?
Probably I'm reading this all wrong.

I was wondering the same thing. There should be no way to pressurize it. Either it should come out the toilet or the vent pipe.

[Jagiven]

Originally Posted by sberry1

At the end of last season, I made the unfortunate error of turning off the wrong water hose after flushing my black tank. I had closed the tank off and later heard a loud bang.

The tank no longer holds any liquid. Nothing comes through the drainpipe if I add water, it all comes out the bottom. I haven't removed the plastic cover on the bottom yet. It was the end of September and I had two weeks left before closure.

If anyone else has experienced this, what should I expect to find once I cut away the under-cover? I've been told a crack that can be sealed. Should I expect to need to replace the entire tank? Any insight into this would be appreciated.

Originally Posted by norty1

If you wait until winter is over, you may not have much of a camping season next year. Until you can get it checked out, there is no way to know.

From your description, it sounds like a pretty big split. Personally, I would not feel good with a patch.

X2, but it should not have split from a tank flush. The tank is an open system. It is open to the roof vent. Any excess water would have bubbled out though the toilet or out the roof vent (there are a number of posts on both happening.

I have two suspicions; the pipe was not properly glued, and it fell out of the fitting, or the gate valve assembly broke. Secondly, the tank fell and it is flowing out of the top of the tank, but this does not support your statement that nothing is coming out of the drain pipe. No matter what, it will be a very messy job. If you have a closed underbelly, I would remove it and let it dry out for the next month or two (don't want mold) and take a few pictures to make a plan for when it is dry. But if it freezes solid cold where you are at, it might be the best time to do this crappy job when it is not dripping on you.

[ShotgunZ71]

I think Norty has been spying on me! Our second trip out on our Jayco, I hooked up all the lines and turned it on. Wife kept saying no water, no water. I'm checking everything. Valves, hoses, etc and nothing is out of place...except I connected the hose to the wrong (black, not white) port. Thankfully, she caught it just as I had gone back out to cut the water off. Just started coming over the toilet lip. I immediately open the black tank valve and drained it all out. Now I know where all the water was going when we didn't have any to the faucets!

[norty1]

Originally Posted by ShotgunZ71

I think Norty has been spying on me!

I have done the very same thing! walking into the rig to see what she was talking about and it hit me. Before I took a running dive for the utility panel, Lynda says "It's almost over the rim!"

[Bill Johnson]

Originally Posted by sberry1

At the end of last season, I made the unfortunate error of turning off the wrong water hose after flushing my black tank. I had closed the tank off and later heard a loud bang.

The tank no longer holds any liquid. Nothing comes through the drainpipe if I add water, it all comes out the bottom. I haven't removed the plastic cover on the bottom yet. It was the end of September and I had two weeks left before closure.

If anyone else has experienced this, what should I expect to find once I cut away the under-cover? I've been told a crack that can be sealed. Should I expect to need to replace the entire tank? Any insight into this would be appreciated.

You say nothing comes out the pipe from the black tank, I'm guessing you blew the drain pipe off the black tank where it connects. Take a look it might be an easy fix

[OnTheGo]

From the way you're describing the leak when you add water to the black tank, it's unlikely it's coming from anywhere near the top of the tank - which would be the toilet or vent pipe connections. That narrows it to a cracked / broken tank or the connection at the discharge (as Jagiven states above). Given all that's been said, the discharge connection is more likely. That could be an easy and inexpensive fix. Hopefully that's the case.





If it were mine, repairing a black tank isn't a consideration. Any structure problem is an automatic replacement.

[Nature Ist]

I have been through a similar issue on my 2020 HT. I ultimately discovered the tank had been forced into place when at the factory, causing a small crack at the vent pipe connector. I was able to repair that, and it has been holding well.
Your situation sounds like a bottom rupture or, as mentioned, possibly a separation of the drain pipe. The only way to address your issue will be to remove the coroplast and access the tank for inspection. It would appear, from your description (particularly the "bang" you heard,) that you will need to replace the tank.
I know of other cases like yours, where overfilling the tank with the flush line has caused enough pressure to rupture the tank. It does happen despite not making much sense because there is a vent to the roof. One thing to remember is that the vent is only 1 1/2" inch diameter, and the outlet can be as much as 10' above the tank. That height equates to 5 PSI of head pressure, plus the flow restriction of the narrow vent pipe, results in increased pressure - these tanks aren't designed to take any pressure at all! Seams and connections are the weak points and will fail when you add the weight of the water and any pressure increase from a high pressure flush.
You are not the first to experience this.

[Texasnick]

I did the same thing in 2020. The lid of the black tank split for about 3 feet where it joins the box section of the bottom part of the tank. There is no reason for this to happen as the water should have overflowed up through the toilet. I spent over $600 for a RV repair center to look at what had happened. They did not find anything? (go figure!). Jayco eventually replaced it under warranty. As a retired mech eng., I inspected the tank after my dealer removed it and it appears to be a manufacturing defect )at the joint between the lid and box or at a minimum, a poor design.

[Texasnick]

The reason my black tank leaked was because the joint between the flat top and main body of the tank split for about 3 feet...I assume this is a manufacturing defect. I also learned this is not an uncommon problem with this tank. I can provide photos if anyone would like to see the problem

[travelingjw]

I vote for the lack of glue or no glue scenario. We recently had to replace an entire garage slab because it was buckling. After digging down 6' to the sewer line and finding no leaks we discovered that when plumbing was assembled someone forgot to glue one of the pipes. The pipe had bee leaking on the other side of a foundation wall.

[Yooper906]

Originally Posted by norty1

It's not like the movie RV at all. I have seen 2 black tanks overflow and both came out of the toilet first. Maybe with a high pressure source the results may be different?

I've not seen that movie. What I'm thinking, there is no way to pressurize a black water tank to bursting pressure, where it's going to split. There is a 2" vent to the roof, no? You have seen 2 black tanks overflow, this doesn't correspond with the posters problem, does it?

[norty1]

Originally Posted by Yooper906

I've not seen that movie. What I'm thinking, there is no way to pressurize a black water tank to bursting pressure, where it's going to split. There is a 2" vent to the roof, no? You have seen 2 black tanks overflow, this doesn't correspond with the posters problem, does it?

Well no it doesn't, but we are offering personnel experiences from real life. I don't know of anyone who knows since it has not been looked at yet. It will be interesting to find out what caused it!

[Bill Johnson]

Originally Posted by norty1

Well no it doesn't, but we are offering personnel experiences from real life. I don't know of anyone who knows since it has not been looked at yet. It will be interesting to find out what caused it!

I think he's from Canada it might be a little cold up there to crawl under and check