cracked elbow in plumbing

Yep, finished now! The view from underneath:

The rubber elbow looks great in there and if it was house flexing or ice in the elbow that cracked it, the rubber one will be a big improvement.

View from above:

The rubber elbow is under the elbow going down on the right. The pipe assembly wanders along the floor, up the side of the door, then back to the sink trap and was an ungainly monster before I put the rubber joint in. I took the opportunity to remove the section connecting to the two sinks and including the trap for cleaning. When I first ran water down the drain, there was a big leak in the cupboard from the trap joint to the drain pipe. There was dirt in the joint. It was sure nice to unhook the rubber joint and take both pieces to the shop to blow them clean.

I just remembered someone mentioning supporting the rubber joints - I must remember to put something under the horizontal run along the floor to support both of them. Thank you for that!

Before I closed off the hole in the floor with white plastic sheeting, I noticed a considerable flow of cool air coming up through it. Hot day, door and vent open - and the hole in the floor was more cooling than the door. I wonder if anyone has seen an RV with a floor vent to take advantage of the cool shade underneath and the natural flow of hot air up and out the roof.

Those Fernco fittings rock

Sounds like you are well on the way to a successful repair!

I cut the pipe! A friend underneath on one end of the hacksaw blade and me in the cupboard and we got it in half an hour. An unanticipated problem immediately showed up. It seems a 1.5 inch ABS pipe is 1.5 inch inside diameter, 1 and 7/8 outside and the flanges on the original ABS elbow are 2.25 inches in outside diameter. The floor "2x2's" are 1.25 inches. The manufacturer squeezed a 2.25 inch elbow into a 1.25 inch space by bending the thin lower plywood and aluminum sheeting! My rubber elbow is even larger - 2 and 3/8 inches. I spent considerable time digging into the top of floor plywood where the rubber flange had to go so it actually fit in without bending the pipe. Hopefully this will eliminate any more pipe cracks.

I am now working on the routine inside cupboard piping which has to be slightly different to accommodate the length losses due to the two cuts that took out the broken elbow. I'm using one rubber joint to make it a little easier to work with, better able to handle road bumps and make it possible to take apart. It also makes cleaning the sink traps considerably easier.

Will post a couple of photos when finished.

I have been working with Forschner drill bits to cut away at the bit of floor above the broken joint that is still inside the cupboard. DW is not keen on messing up the floor outside the cupboard. While doing this with the inside cupboard pipes loosened from the sinks, the cracked joint broke completely.

I can now see all of the top of the broken joint (just barely) so I may be able to cut it off with something like a hacksaw blade. It looks like I can manage the half inch loss of length by rebuilding part of the inside cupboard pipes to take advantage of the enlarged hole.

Access to the top of the broken joint also makes it possible to repair the joint as some of you suggested. ABS solvent supported by fiberglass or a pipe patch product perhaps. I could use a rubber joint in the cupboard piping to gain a bit of flexibility.

I am torn between the two approaches. And it is a little too hot to work today.

Whatever I do, I will certainly leave my under floor opening accessible for checking - and for dripping water if my first try fails on the next camping trip.

You might think if you could replace the whole length of pipe going up to under the sink, then only a short piece out of the other end of new elbow and the a rubber coupling between it and the old long piece.

mobeewan wrote:
If the elbow is a short radius elbow and there is enough existing pipe to glue to on both ends once it is cut out, you can cut out the existing elbow and glue in the longer radius elbow.

short radius 90 deg elbow

long radius 90 deg elbow

Also, a good idea. Forgot about the long radius option.

You could look at "rescue tape"

Two or three possible fixes.

First; The proper way: Replace the fitting (What else)

Second: Foxy Poxy, sold at swimming pool supply houses, works when wet

Thrid (This only works when dry.. GOOP.. Plumbers, automotive RV or Household all will work, try to work it into the crack and let dry at least 24 hours.

I agree with the advice above on the flexible repair elbow. It will work fine provided the drain pipe is supported adequately and does not move around. I would also make the access hole you cut out a real access "door" by making a removable door or plate of suitable material so you can remove it and check the repair from time to time.