Replace metal drain pipe in house?

[MariaAZ]

What started as a simple project has turned complicated (but don't they all?)

We had a leak from behind the wall under the bathroom sink. Cutting away a bit of the wallboard, I discovered that the fitting connecting the sink drain to a T fitting on drain line had a piece rotted out, causing the leak. No problem, a quick trip to the hardware store and a new plastic piece was installed (it's the bit with the plastic screwed in). Ran water in the kitchen sink (which connects to the opposite part of the T fitting) and much to my dismay, I found another leak, this one on the pipe that connects the T fitting to the actual drain line. In the photo below, it's right at the collar of the T fitting where the drain pipe goes into.

The drain pipe itself runs about 3 feet to an elbow that goes down to the sewer line. It is one solid span until it gets to this section of wall where it ends behind the handle of the water supply line. You can't see it well, but this stretch of pipe screws into a fitting. Between this fitting and the T fitting to the drains is a short piece of pipe threaded on both sides. You can barely see where this piece screws into the fitting just to the left of the black plastic-wrapped water line going through the wall to under the kitchen sink.

Now, the question is... how to replace it? Should I remove the entire pipe to the elbow to the sewer and replace it with black plastic (which is the material of choice of the hardware store though they DO sell metal pipe as well), or should I just replace the affect part? In either case, what's the best way to get the pipe out? I have a Sawsall and air compressor if I need it, but I'd like to do as little damage as possible

[Curtis B]

Take your sawsall and cut the pipein the best place you can find. Get the black ABS pipe and the fittings neededfor the sinks, the Tee and the straight pipe. You connect the ABS to the iron pipe with a no hub fitting ( the hardware store people should know what it is).

[MariaAZ]

Thanks! I think it would be a tight fit to try cutting between the stud on the left and all the water lines. Would it be advisable to try it anyway so all fittings are in the same piece of wall, or would cutting to the left of the stud be OK?


ETA - we've been thinking about adding a dishwasher, which would actually be farther left than the stud on the left. If we cut there and replace with ABS, is there a special fitting one uses for dishwashers that we can install now?

[Curtis B]

It is kinda hard to tell you where to cut w/o being there. The thing to remember is that you will have to put the pipe back through the hole in the stud, so don't cut the pipe to long or you will never get it through there. If you will be adding the dishwasher then now is the time to plumb for it so you don't have to open the wall again.

[rancher1913]

if you can, use white pvc instead of the black abs---the abs will sometimes come apart over time and you only want to mess with it once.
add a studor vent at your sink and it will drain a lot better--sometimes called a boca vent or air admitance valve.
you might want to add a cleanout fitting so you can rodd the line in the future.

[MariaAZ]

Curtis, I was wondering if that's why that little 3-4" piece of threaded pipe is between the T fitting and the rest of the pipe... because it was the only (or best) way to get the pipe installed.

Rancher, thanks for the tip on the vents. We have had problems with the drains being sluggish, so that valve sounds like a good idea as does the cleanout. Since we are replacing the pipe anyway, I could put the cleanout on the kitchen side; it would have been nice to have in the past!

[rzrubek]

If i remember correctly the dishwasher has all its plumbing under the sink. At least the one i installed did. There is a special down pipe from one of the drains with a one inch or so nipple sticking out and that is what the dishwasher drians into. AS far as the metal drain pipes, get rid of as much of the metal pipe as possible. I had the same exact problem in a house we rented, the metal drains just rotted.

[Curtis B]

Originally Posted by MariaAZ

Curtis, I was wondering if that's why that little 3-4" piece of threaded pipe is between the T fitting and the rest of the pipe... because it was the only (or best) way to get the pipe installed.

Rancher, thanks for the tip on the vents. We have had problems with the drains being sluggish, so that valve sounds like a good idea as does the cleanout. Since we are replacing the pipe anyway, I could put the cleanout on the kitchen side; it would have been nice to have in the past!

It is possible that is why that nipple is there, or the length of pipe was just short that much. Now that I have had time to think about it rancher is right you should install the vent, espcially if you are installing a dishwasher. The best way would be to take the pipe out all the way to the 90, and replace the 90 with a part called a "sani T" , again the store should know the part. Make sure the T sweeps down and on the upper part of the T put the vent in, another name for it is an "auto vent". Most dishwashers are plumbed into a garbage disposal, since there are usually food particals in the water they pump out, so you sould try to put it as close to the vertical pipe going down to reduce the risks of a clog.

[65284]

Just don't do what I did. I replaced bad piping behind the slop sink in the utility room, was all finished, and had even replaced the tile on the wall. Then I found a puddle of water the next morning.

I had to tear the wall open again and discovered I had hit the copper supply line, running horizontally through the studs to the washer with a sheetrock nail when I patched the repair hole. I had nicked it just enough for it to seep. And I thought I hated plumbing work before I started that job.

[MariaAZ]

Originally Posted by 65284

Just don't do what I did. I replaced bad piping behind the slop sink in the utility room, was all finished, and had even replaced the tile on the wall. Then I found a puddle of water the next morning.

I had to tear the wall open again and discovered I had hit the copper supply line, running horizontally through the studs to the washer with a sheetrock nail when I patched the repair hole. I had nicked it just enough for it to seep. And I thought I hated plumbing work before I started that job.

This is exactly my fear! On the one hand, I want to save the money plus gain experience (I love doing repair-type stuff, nothing better than knowing I did it myself) but on the other hand, I don't want to pay MORE to have my mistakes corrected! I'm a bit worried about taking the elbow off the sewer line, thinking "oh my gosh, what happens if I break that pipe?" or, like you, nicking a water line. I plan to mark stud locations when it's time to close the wall (which I don't plan on doing for a bit so as to make sure there are no leaks). And after that, I'll be back asking how to remove and replace a 5 ft wide tub in a 5 ft wide bathroom

The pressure's on as this is the only bathroom in the house....