Thursday, June 1, 2023


RV Shrink: Black tank outlet cracked – Can it be fixed?

Dear RV Shrink:
We just started a trip that will last two months. We have a 1989 travel trailer. It seems our exposed plumbing outlet for the black water tank is cracked right where it is connected to the tank. It is a slow, steady, smelly drip. Every time my husband tries some new super-duper glue or filler, he tells me it’s fixed. Every time I tell him it’s leaking again he gets mad and frustrated.

I know it’s a lousy job and hard to deal with on a trip, but I just can’t stand smelling like an outhouse every place we park. Should I just put up with it or keep giving him the stink eye. —Odiferous in Oregon

Dear Odi:
In your husband’s defense, these are some of the hardest leaks to deal with and actually fix without having the tank replaced. There are many products that claim to be “stop leak” for ABS plastic, but they do not often work for any length of time.

Not letting it drip onto the ground should be your first course of action. Put some sewer deodorizer into a small bucket and contain it.

If you can completely dump and dry the area around the suspected crack, I may have a solution for you, no pun intended. I have used this several times in the past and it seems to work better than anything else I have come up with.

Get a small ABS fitting and grind or break it into very small pieces. I use a bench grinder that turns the ABS into thin, semi-melted, ribbon-like pieces. Gather this material into a small can and add Acetone until it covers all the ABS pieces. Let this set for a couple hours, stirring occasionally. You will end up with ABS paste.

By applying this paste to the dry, roughened area around the crack, the solution should meld into the fitting and crack. Let this dry and then add a couple more layers if needed. If nothing else it should last the rest of your trip.

Often a new tank is the only remedy, which should be pretty straightforward if the tank is exposed. So work on this together and stop giving your husband the ol’ stink eye. —Keep Smilin’, Richard Mallery a.k.a. Dr. R.V. Shrink

Can’t get enough of the Shrink? Read his e-books, including Book 2 in his two-book series: Dr. R.V. Shrink: Everything you ever wanted to know about the RV Lifestyle but were afraid to ask or check out his other e-books.



0 0 votes
Article Rating
Subscribe to comments
Notify of

This site uses Akismet to reduce spam. Learn how your comment data is processed.

Inline Feedbacks
View all comments
2 years ago

A lot of tanks are made with polyethylene resin and if so, is almost impossible to repair. The only sure way is to heat melt it back together. So test your tank to determine its properties before attempting to ‘glue’ it.

3 years ago

Take a look at Plast-aid. I have used it successfully on pvc leaks and their website says it sticks to ABS.

3 years ago

Had this very same leak problem the past 3 years. Finally bought another motorhome. Expensive fix. In those 3 year I think I tried every solution for a patch except having a plastic welder do a mend. My little crack was at the top of the outlet of the black water tank, where the 4″ stub connects to the “tee” handle apparatus. The crack was just big enough to get your fingernail in, right a the point, that if you have 4″ of sludge, it going to leak id not patched. I would dissemble, dry, clean, rough up, clean up with a myriad of products and meshes (to include the above “trick”). Many products worked great and I was a happy camper on occasions. I built a little brace to relieve the pressure on the joint and reduce the vibration. Poor design to have dual tee handles and associated ABS fitting just hanging there from the stub on the black tank. Eventually all patch jobs failed as urine is very corrosive and over time the patch would come off, usually as one piece. I dealt with the messes the writer talks about, the drips and the odors. One solution I found was to leave the T-handle open while parked in a site, therefore not allowing the 4″ to accumulate in the tank. But bad idea to leave the handle open (another subject for a later date) and sewage is never completely empty and will seep out during movement. Good luck on getting that patched

Vic Whitmore
3 years ago

If the leak is simply a crack, it is very simple to fix. The best “glue” you can use is ABS primer. The primer will seep into the crack and slightly dissolve the surface of the material. If you can, apply some small pressure on the fitting to get the crack open, in order to ensure the primer can fully seep into the crack. Now apply the pressure to hold the crack closed and the dissolved surfaces will mate together. Hold the crack closed for at least a few minutes.
I fixed my grey tank where the outlet is reduced down into the pipe size going to the gate valve. It has never leaked in the three years since. I also fixed a leak in my swimming pool skimmer where the bottom fitting meets the line to the pump. That has not leaked in over ten years. I have used the same application to fix leaks in my solar collector plumbing.
AB S primer is a plumbers best friend!

3 years ago

I’ve had good luck with a product called SealAll, in a yellow tube $2/oz. Gas and waterproof, sticks pretty well.

The acetone trick works well, just watch fumes. Slightly kinder is (still high VOC) normal PVC cement used for glueing pipe.

Sign up for the

RVtravel Newsletter

Sign up and receive 3 FREE RV Checklists: Set-Up, Take-Down and Packing List.