Broken ABS sch40 1-1/2" bathroom drain pipe.

[dddd]

I had a leak appear yesterday in my downstairs hallway ceiling, turned out to be a broken horizontal black ABS pipe that is the upstairs bathroom drain.

I emergency-fixed it with a rubber coupler after using a saw to complete the break. There is a 1/2" wide chunk of the pipe missing now from about 1/3 of the way around one of the pipe ends.

I mostly want to know why this failed. Should there have been some length-wise flex in the plumbing to accommodate heat expansion? It felt very rigid as far as my not being able to pull the ends of the pipe apart, which had me thinking that there should maybe be some pipe flex somewhere in this direction.

And should I make the inside smoother now because of that missing chip/strip off the end of one of the pipe ends.

I should add that the location is closer to the end of the pipe where it turns 90 degrees toward the lower level, so one to three yards from any of the bathroom fixtures.

This house is about 25 years old. I noted some rot (and rust of the drywall screw) so this had been at least seeping for perhaps a year by now.

Thanks in advance for reading, and here is a picture after I joined it for now.

 

[Reach4]

That black plastic is ABS.

I emergency-fixed it with a rubber coupler after using a saw to complete the break. There is a 1/2" wide chunk of the pipe missing now from about 1/3 of the way around one of the pipe ends.

I mostly want to know why this failed. Should there have been some length-wise flex in the plumbing to accommodate heat expansion? It felt very rigid as far as my not being able to pull the ends of the pipe apart, which had me thinking that there should maybe be some pipe flex somewhere in this direction.

And should I make the inside smoother now because of that missing chip/strip off the end of one of the pipe ends.

Officially you should not use a flex coupling, but instead should use a shielded/banded coupling, which surrounds the rubber with a stainless steel band.

The piece you cut out -- what does it look like? Does it show the failure point?

 

[Sponsor]

 

[dddd]

Thanks Reach4, you're right that I described the plastic using the wrong three letters, I stand corrected.

A friend just told me that I was also wrong about how this bathroom is plumbed, that only the sink empties into this 1-1/2" ABS pipe.
So I have much less to worry about with the inside surface having that missing chip where I sawed it.

I may still wrap the rubber with a couple of layers of good beer-can stock from one of the larger-diameter size cans (my favorite size, what a coincidence). Then maybe two of my industrial-grade zip-ties will hold that in place.

This being only the sink drain, I'm suspecting the pipe may have somehow been damaged decades ago along it's journey to it's present location, a small crack that eventually made it's way around the pipe(?).

 

[Reach4]

I may still wrap the rubber with a couple of layers of good beer-can stock from one of the larger-diameter size cans (my favorite size, what a coincidence). Then maybe two of my industrial-grade zip-ties will hold that in place.

Another alternative is to get a shielded coupler made for 1-1/2 inch plastic pipe.

The official solution would be to totally replace your rubber piece, and the other way would be to take the 2 clamps off of your rubber piece, and put the stainless band around your rubber piece instead.

 

[dddd]

Thanks, I saw those parts at the store but chose one that had more overlap length to it.

I have a new/old problem now.
I was putting in a horizontal 2x2 support under the pipe using just glue and wedging action when I discovered that there was a second, identical crack around this pipe, just a few inches from my repair, and then another, just six inches further along (and where there is no access from the 10"x10" hole that I cut in the drywall.

And suddenly there were water drops coming out of the door frame, a foot away on the other side of the coupling (from this same piece of pipe but where I can't see).
It seems the cracks all start with a full 180 degrees of crack around the lower half of the pipe's diameter. Water droplets appear instantly as I flex the coupling up and down.

It's like this pipe has some material defect to it, super brittle or something. I'm now thinking that the whole pipe needs replacement, and that access to the ends will require expensive demo and repair unless I can run a flex pipe down it's length to seal it up.

Again, the cracks travel perfectly around the pipe. The first thing I noticed was that when I flexed the pipe slightly I noticed a line of water droplets suddenly appear along a circumferential crack line.
Thinking that perhaps I won't even need a saw this time, that I could probably snap the pipe in half with a twist of my hand.

 

[dddd]

After surveying my bathroom and plumbing, I'm thinking that the practical fix is going to be running this sink's drain pipe through the base of the vanity, and tee-ing the pipe into the other sink's drain pipe. It's about the usual four feet away, making me wonder why it wasn't done this way originally(?).
This would be a piece of cake IF I had any reason to replace the original, right-angle mirror vanity.
As it is, it looks to be pretty well built-in, and I kind of hate to run the new pipe through the cabinet itself.

The scary part is that maybe this faulty pipe is also coming apart in other places in this house (???).

I have no experience refinishing a textured-wall repair either.

 

[Jeff H Young]

dont want to worry you, but inform you Ive heard of some known cases of abs cracking like this and basicaly it could be a case of bad pipe if you can get a picture of all the writing on the pipe including manufacture date you might either rest assured yours isnt the case or decide to remove some of it. It can also crack from other reasons and might be fine with simple repair. the problem of bad abs pipe was over 20 years ago im not sure coulda been 30 probebly can google it if interested

 

[dddd]

Hi, yes I googled that and found that 1980's ABS pipe from certain vendors ad/or batches was prone to cracking. My house was built in the early late 90's.

ABS left out in the sun for an extended time, or that had very hot water running through is also said to be prone to cracking.

What I notice is that these cracks form along the lower half of the pipe, so it seems like where the water flow was in contact with the plastic is where there are now cracks appearing.

Would an unsupported length of about four feet be a possible cause of this cracking?

 

[Jeff H Young]

I doubt unsupported 4 foot would crack , Its not suppossed to be that brittle , Short amounts of time several days in sun tend to warp and bow the pipe after all these years never studyied " what if" it was in sun too long I figured some sort of failure . Ive run pretty darn hot water never had problem. It could have been caused by many things, had cracks been on top might not have noticed a leak. I would try to identify manufacture and remove a bigger piece and do some personal testing to figure out if its brittle . or perhaps installed damaged, happens all the time .

 

[dddd]

Following up, I finally measured the exact unsupported length of this pipe after noticing a tell-tale pattern of slightly-diagonal cracks in series/parallel that form each crack that I found. This pattern of micro-cracks looked identical to tension-stress cracks of the type I've seen many times on old plastic clamps that eventually failed in tension after many years and decades.
The rated maximum unsupported length for this sch40 ABS pipe at 120F temperature is only 3-1/2 feet, but here this pipe had an unsupported length of 5'3", and finally showed failure after 25 years.
The sag also put bending stress into the pipe just to the other side of one of the supports, where it has most likely started leaking adjacent to an elbow at the end of the pipe (where the water then dripped into the door frame, but where I can't see).

Since that end of the pipe's support is a full block kicker brace with a hole in it spanning the two joists, I will have to cut it out with a sawzall to access the failure at or below the elbow, which is directly inside the main load-bearing wall holding up the house and the edge of the cement garage floor slab.

I'm still thinking that the sag stress along the bottom side of the pipe's circumference was made worse by the pipe's length expansion each time that hot water passed through it. This would have caused the pipe to bow yet further in the direction of the sag as the bottom of the pipe expanded more than the cooler top of the pipe. So I will be checking for adequate pipe clearance at the hole in the floor near the sink's vertical down pipe (under the trap).

One more question if I may ask:
The leak I can't yet see that is within the central load-bearing wall will probably turn out to be a cracked vertical 1-1/2" ABS pipe that is glued into a 4" pipe's tee. If the crack is very close to the tee, How would I get a new piece of 1-1/2" pipe to connect to that big tee? This big tee would be nearly impossible to replace as it is boxed in with many loaded structural members, so I may have to connect a new piece of 1-1/2" pipe into it somehow. Can the old pipe be reamed out, or would I perhaps have to have a copper sleeve custom made to fit to the pipe's ID and create a solid joint?

Thanks everybody for all the advice so far, I'm hoping that the end of my leaking problem is in sight!

 

[Reach4]

Can the old pipe be reamed out

Check out "socket saver" and Rambit.

 

[Jeff H Young]

Dont you trust just cutting it near the tee? glue a coupling on covering the rest of the crack prone piece withe the coupling heavey on the glue. socket saver or rambits work great but I wouldnt buy the tool (they are kinda cheap though) unless you do a fair share of plumbing but Reach 4 idea is good perhaps a bit tidyier fix I avoid hogging out the inside of a fitting but thats just me , nothing wrong with it. 5 foot 3 without support not good so get a block plumber tape or something in there. on job sites pipe gets run over by a car or equipment coulda been damaged on install. save that old pipe might have recource or a reacurrance