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

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


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… Read more »

Vic Whitmore

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… Read more »


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.