Black tank dump piping fell off tank

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Black tank dump piping fell off tank

August 03, 2021, 11:42:59 am

We own a 2015 27MB. Today the black tank dump piping fell off the tank. Nothing seems to be broken and it seem I should be able to clean it all up and reattach the piping to the tank. There were two hose clamps on the connection, but I don't see any evidence of any sealant/caulking/glue. Is there an appropriate/necessary product to cover the mateing surfaces?

Also there was no support structure for this pipe run and the dump valve at the end. Has anyone added pipe supports? If so any advice on what might work?

Thanks
Geoff

Re: Black tank dump piping fell off tank

Reply #1 – August 03, 2021, 11:45:53 am

The answers are yes and yes! Should be sealant and support. With that recent vintage, I’d give the factory a quick call and get current best practice.

Re: Black tank dump piping fell off tank

Reply #2 – August 03, 2021, 12:15:19 pm

That's a bit disturbing! Agreed, I would call the Mothership. Might want to send a photo to Todd so he can see for himself. Please let us know the resolution in this thread. Now I better go inspect mine since it's the same vintage MB.

Re: Black tank dump piping fell off tank

Reply #3 – August 03, 2021, 12:20:52 pm

It could be that the tank is Polyethylene and the pipe is PVC.

That's a hard connection to make with sealant. Mechanical connections are commonly used.

Rich

Re: Black tank dump piping fell off tank

Reply #4 – August 03, 2021, 12:27:09 pm

The earlier MBs black tank PVC pipe/valve did not have a support system. For example, our ‘09 MB is just as described by Geoff. I’ve removed the valve several times for different reasons. The first time, there was some kind of sealant, which I cleaned off. Now, I simply use the two (2) clamps with no ill effects.

Sometime after 2009, the factory installed some kind of a support bracket, which they don’t sell. I’m guessing this was a 2016 or later black tank modification.

Re: Black tank dump piping fell off tank

Reply #5 – August 03, 2021, 12:59:13 pm

Called the factory. They were surprised the pipe fell off. It must not happen very often.

They recommended using an ABS pipe joint compound and hose clamps. They did not recommend adding any kind of a pipe support.

Thus far the worst part of the job has been the clean up, it occurred at our campsite as we were attempting to attached the sewer hose. The reattachment process looks like it will be very simple and straightforward.

Geoff

Re: Black tank dump piping fell off tank

Reply #6 – August 03, 2021, 01:06:45 pm

What exactly fell off? The valve or a piece of pipe? A photo would help.
The dumps valves are clamped and not glued, glueing would make replacement impossible. The may use a removable sealant to seal the valve, one application where silocne maybe useful, it doesn’t permanently stick to ABS.

Larry

Re: Black tank dump piping fell off tank

Reply #7 – August 03, 2021, 01:10:19 pm

If it were me, I'd add a support using plumber's strapping. This stainless steel strap looks as if it might do the job.

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Re: Black tank dump piping fell off tank

Reply #8 – August 03, 2021, 01:48:15 pm

The pipe (not the valve) fell off. My first attempt at adding a photo, hope it worked.

Geof

Re: Black tank dump piping fell off tank

Reply #9 – August 03, 2021, 02:06:19 pm

Geof-

Our black tank outlet assembly came loose. After I put it back together I added a strap to the skirt. I debated doing so; without, the assembly moves as one with the tank; with a strap the assembly will tend to twist at the tank collar ( and potentially leak). In the end, the idea of not having the assembly come loose on the road again won. A dissatisfyingly-almost-unhelpful picture is here.

We sold the coach shortly after, so I don’t know how well the fix worked.

I seem to remember using polyethylene caulk in the joint when reassembling it.

Mark H.

Re: Black tank dump piping fell off tank

Reply #10 – August 03, 2021, 02:24:18 pm

If you notice that the generator exhaust pipe uses a flexible rubber strap to support the pipes weight. It makes me wonder if a rubber strap similar to the exhaust strap would provide the support for the dump valve while not being “inflexible”.

Just a thought.

Kent

Re: Black tank dump piping fell off tank

Reply #11 – August 03, 2021, 02:31:00 pm

We had the same thing happen to us while camping in 2017 in our then new-to-us 2011 MB. We were very fortunate in that the valve and piping fell off just after we had dumped and I was closing the valve. We simply reattached using the existing hose clamps and were on our way. We posted about the incident on the forum: Yucky story about dumping the black tank.

After much consideration, we decided not to add a support because we think the support has the potential to do more harm than good. Maybe this is the Mothership's rationale too.

OK...I think I'll go check those hose clamps now.

Jim

Re: Black tank dump piping fell off tank

Reply #12 – August 03, 2021, 03:55:04 pm

Well its all back together and has passed a leak test. Decided against the support strap idea for the reasons mentioned above.

Thank you all for your input and suggestions. You all helped to keep our day from spiraling any further than it already had. The failure happened while we were dumping, it was quite spectacular and MDW was in the splash zone, I'll leave it at that.

Geoff

Re: Black tank dump piping fell off tank

Reply #13 – August 03, 2021, 04:35:40 pm

Quote from: Syzygy - August 03, 2021, 03:55:04 pm

The failure happened while we were dumping, it was quite spectacular and MDW was in the splash zone, I'll leave it at that.

Good to hear all is well now, Geoff. I'm afraid if that happened to my DW, our RVing adventures would be immediately over so hats off to your bride; you can both laugh about it now! Now's a good time to pull this out of the vault for a little levity:

https://www.youtube.com/watch?v=-C0bpTLEmZw

Re: Black tank dump piping fell off tank

Reply #14 – August 14, 2021, 10:57:24 am

Got under Nocona to take a close look at the black tank piping. It’s a very short run but I did notice a place where it looks like the factory had put in a support which is now not attached. Wondering if I should reattach it? Also, does anyone know the size of the hose clamp needed as I would like to have a spare on board just in case the existing one breaks?

Re: Black tank dump piping fell off tank

Reply #15 – August 14, 2021, 11:16:37 am

"...it looks like the factory had put in a support which is now not attached. Wondering if I should reattach it?"
---
Considering the potential for the pipe dropping/breaking, and subsequent spillage, re-bolting seems to me like a real good plan!

Re: Black tank dump piping fell off tank

Reply #16 – August 14, 2021, 12:25:48 pm

Hi Greg; That pipe up to the back of the gate valve is filled with liquid from the get go as you drive down the road. So that weight is trying to rotate and loosen the hose clamp fitting. I would put a rubber grommet in one of those holes and a SS screw through the center to support that, but not have a solid connection.
My old Emerald Onan generator has an external exhaust pipe with a rubber section attached to the skirt and the pipe. Of course the generator flexes and moves more than the black tank, but kind of the same idea. Speedway Poly Exhaust Hanger Grommet Bushings RonB

Re: Black tank dump piping fell off tank

Reply #17 – August 14, 2021, 01:22:22 pm

Thanks, Ron and Joan for your responses. I was able to find a rubber grommet to fill that gap in my parts and pieces bin and did a temporary fix until I can get down to Home Depot and get some stainless steel hardware.

Re: Black tank dump piping fell off tank

Reply #18 – August 14, 2021, 06:51:25 pm

I really like this idea. I think I’ll add a second L bracket on the other side of the valve to share any stress from movement. And do the same on the gray tank valve. I believe I’ll add a nylon washers under the bolt heads too. Again to reduce pressure on the fiberglass from the bolts. Thank you for sharing the above pictures.

Re: Black tank dump piping fell off tank

Reply #19 – August 14, 2021, 07:07:24 pm

You're welcome, Ed! You may not need to do anything to the gray piping if it's anything like mine. I checked it out when I was fiddling with the black valve and the gray piping appears to be mounted securely in two places before going into the tank. Let us know what you find!

Re: Black tank dump piping fell off tank

Reply #20 – August 14, 2021, 08:09:46 pm

Corollary to supporting the dump lines: check the tightness of the mounting bolts for the black and grey tanks.

Re: Black tank dump piping fell off tank

Reply #21 – August 14, 2021, 08:27:38 pm

Quote from: Joan - August 14, 2021, 08:09:46 pm

Corollary to supporting the dump lines: check the tightness of the mounting bolts for the black and grey tanks.

Dang, Joan, now I have to make another trip under the RV!

Re: Black tank dump piping fell off tank

Reply #22 – August 14, 2021, 08:34:03 pm

Just trying to be helpful!

Re: Black tank dump piping fell off tank

Reply #23 – August 15, 2021, 12:01:33 am

Tightening the hose clamps that hold the dump valve's plumbing to the holding tanks is another thing to add to the annual maintenance list.
For an extra secure and leak-proof job, coat the inside of the connection with Goop or one of its variations, such as E6000, available at any big box hardware store.
Amazon.com: Amazing Goop 140211 3.7 oz. All Purpose Adhesive, Clear : Arts,...

Larry

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Re: Black tank dump piping fell off tank

Reply #24 – August 15, 2021, 11:28:02 am

I really like the rubber bushing solution. Looks like a winner.
Dave

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