1980s Bigfoot trailer blackwater tank

[Longkilt]

I bought a Bigfoot trailer a few weeks ago and have been busy replacing all the plumbing lines. I installed a new grey water tank and replaced all the 1.5" lines under the trailer but I have discovered that the 3" black water pipe and elbow has a hair line split on the bottom. Question is has anyone replaced their 3" pipe and if so is it threaded into the bottom of the black water tank? Can I cut the elbow and thread out the joint from under the trailer easily without having to remove the toilet and tank from above?
The previous owner apparently drove away with the sewer discharge still attached and tore everything apart under the trailer. I was really hoping the 3" pipes were sound as they looked fine but now they gotta go.
I was thinking about trying to patch the split with ABS glue on the inside and outside and a couple hose clamps but I would rater replace if I don't have to remove the toilet and tank. Unfortunately in order to thread out the pipe I would have to cut the pipe at the elbow to get past the frame when turning... means there would be no turning back.
Any advice from previous plumbers would be appreciated!

[Borrego Dave]

I would go the easy way first with this. Use the ABS glue as it's not a pressure line should work fine.

[Steve Outlaw]

If you can get to the hairline crack from the inside, you can repair it with the ABS glue. Clean the area well, apply liberally and let dry. I would also apply the glue to the outside. I assume the crack is on the bottom of the pipe and the only problem here will be a tendency for the glue to want to drip off.

[mszabo]

Melt it back together!

[Longkilt]

The crack is on the bottom of the elbow as well as about a 24" length of 3" pipe. I should be able to get to the inside so I will try ABS solvent on both sides of crack and then tighten 2 or three hose clamps. I'll try to remember to take some pictures of the repair attempt and report back with the results. Thanks for the advice guys! I think the repair attempt might save a huge hassle of replacing pipe.

[Borrego Dave]

Mike, I wouldn't use any clamps on it, remember there's no pressure on it. A $4 can of ABS glue is cheap.

[Gardnpondr]

Wondering how it held for him? Would love to know in case we have to fix any of these things on our old one. :-)

[Borrego Dave]

Originally Posted by Gardnpondr

Wondering how it held for him? Would love to know in case we have to fix any of these things on our old one. :-)

Good question.....must have worked or we should have heard about it. Kind of like newbies listing trailers for sale and never letting us know they have been sold

[Gardnpondr]

I sure would like an update because I might have to do something like this with mine. I'd have to cut my shower stall all to pieces just to get it out the bathroom door UNLESS I could get at it UNDER the camper. Mine sits UNDER the shower stall.