Replacing a copper drain pipe inside a wall

[LikeABigFriedEgg]

My kitchen-sink drain pipe is leaking in my 50-year-old house. The pipe drains a two-bowl sink, garbage disposal, and dishwasher. It is 1.5" nominal copper and runs for about seven feet inside a wall. It seems that it passes through 2" holes through the studs in the wall. I'm not inclined to buy copper to replace it.

Would it be normal to replace the copper with PVC? I think I probably won't be able to fit 1.5" nominal PVC through the holes in the studs. Should I replace it with 1.25" nominal Schedule 40? I'm not sure, since the inner cross-sectional area of the PVC is only about 5/6 as big as the area of the copper.

 

[Plumber69]

1.25 is undersized for kitchen

 

[Sponsor]

 

[Terry]

New kitchen installs are 2" until the vent and then 1.5" for the trap arm and trap.
There is no way I would run 1.25" for a kitchen. I would bite the bullet and buy some copper for that if you aren't increasing the hole sizing.

 

[LikeABigFriedEgg]

How could I go about enlarging the holes?

 

[Terry]

How could I go about enlarging the holes?

To enlarge the holes, you would need to have access. To make an existing hole larger, also a way of centering the bit. Sometimes that means screwing some think plywood over the holes, then making your marks with a level, making sure you have proper 1/4" per foot grade. Since you don't have the center all the way through, it's a bit tricky keeping the holes aligned while drilling. Sometimes it's easier to just go with a new location.

 

[LikeABigFriedEgg]

I don't think I can relocate the drain pipe, as the kitchen is atop a slab, and the pipe leads seven feet horizontally above the slab, to the basement (then it has an eight-foot vertical drop, then into the basement floor). Hot and cold water pipes are in the same wall, coming from the basement. I don't think there is any wiring or anything else in that part of wall.

I was thinking the holes through the studs could be reamed bigger using a reamer on a long shaft. Does anyone ever do anything like that?

 

[LikeABigFriedEgg]

The OD of 1.5" PVC is 1.9", and I think the holes are 2". Would it have been standard practice to cut the holes to match the slope of the pipe? I mean would the plumber have drilled the holes at a slant? If so, I would think there would be a good chance of ramming a new 1.5" PVC pipe through there, if I fashion something like a nose cone on the end of the new pipe. But if the holes were drilled horizontally, they would be too tight for 1.5" PVC.

 

[LikeABigFriedEgg]

Oh oh, I just noticed that the copper pipe isn't as expensive as I thought. I notice I can get a 10' length of 1.5" type L for $50, available from the local big-box store. I thought it was going to be three or four times that much. So I will just use that.

Is type L correct for this application?

 

[Cwhyu2]

Oh oh, I just noticed that the copper pipe isn't as expensive as I thought. I notice I can get a 10' length of 1.5" type L for $50, available from the local big-box store. I thought it was going to be three or four times that much. So I will just use that.

Is type L correct for this application?

They also make DWV grade copper tube which would be cheaper than L copper.DWV copper yellow markings type M copper red markings type L copper blue markings type K copper green markings.

 

[Reach4]

They also make DWV grade copper tube which would be cheaper than L copper.DWV copper yellow markings type M copper red markings type L copper blue markings type K copper green markings.

Given that his copper line got eaten thru, it could make sense to use heavier copper than the minimum.

Of course the original copper might have had to face chemicals that the new line will not have to face.

 

[Cwhyu2]

Also another thing to consider is that the DWV copper fitting may not be very forgiving when it comes time to insert the thicker wall copper tubing into the DWV fitting.

 

[LikeABigFriedEgg]

Also another thing to consider is that the DWV copper fitting may not be very forgiving when it comes time to insert the thicker wall copper tubing into the DWV fitting.

Hmmm ... I'm puzzled by this ... I thought the OD of the pipes was constant across all the types, but that the ID of the pipes was what varied. And similarly, that the ID of the female fittings was constant across types.

Edit: Maybe you're referring to the radii of the two elbows shown.

 

[LikeABigFriedEgg]

Menards' stock and pricing are a little funny. Ten feet of DWV and ten feet of L cost the same, and they don't have M or K in ten foot lengths.

 

[Dj2]

Menards' stock and pricing are a little funny. Ten feet of DWV and ten feet of L cost the same, and they don't have M or K in ten foot lengths.

Do they offer free shipping to the west coast?
I'll take a bunch of Ls.

 

[Reach4]

Do they offer free shipping to the west coast?

No. Free shipping to stores, but you are not near any of their stores.

 

[LikeABigFriedEgg]

Lucky, I guess. Lowe's and Home Depot don't seem to have it. I was looking at McM-Carr previously, the high price making me want to buy plastic. You can do okay on ebay for shippable lengths (6 feet max, I think) of copper. Not sure that a coupling would be small enough to slide through the holes in the studs though. A ten-foot off-the-shelf section happens to be very comfortable for this job.

I have several other 1.5" copper drains and vents in the house, and some of them are accessible. I had been considering cannibalizing those for this in-wall replacement and replacing them with 1.5" PVC.

 

[LikeABigFriedEgg]

Thanks Plumber69 and Terry for a quick definite answer about the drain size. Thanks everyone else for your help too. I see a plan involving a new copper pipe becoming clearer.

Reach4, I have reason to think you're right about chemicals eating the pipe. I know that the previous proprietor had a habit of using Liquid Plumber and similar. I've stopped softening my (31 grains) water in the last year or two also---would that have any effect? The drain has a history of blockage, and it has been snaked by a plumber before too---so maybe there has also been physical damage to the pipe?

Besides the leaky seven-foot section, there is under the sink an assembly having a wye and an elbow and a couple male adapters, and I'll have to inspect those parts for possible replacement.

 

[Reach4]

Reach4, I have reason to think you're right about chemicals eating the pipe. I know that the previous proprietor had a habit of using Liquid Plumber and similar. I've stopped softening my (31 grains) water in the last year or two also---would that have any effect?

Softening could make the water slightly more corrosive, but leaving it hard could contribute to deposits that might cause more cleaning efforts due to clogging. I sure would not want to give up softening. Do you have a corrosivity number for your water?

I think your copper replacement will last fine if you don't hit it with the strong drain cleaners.

To put in the new pipe, you will probably need some couplers to allow you to saw the pipe and piece it back together in the wall. If you are adverse to soldering, Proflex 3003-150 banded couplers will work at a cost premium.

 

[LikeABigFriedEgg]

To put in the new pipe, you will probably need some couplers to allow you to saw the pipe and piece it back together in the wall. If you are adverse to soldering, Proflex 3003-150 banded couplers will work at a cost premium.

Yes, I think one of the studs will be crowding the pipes, and I'll have to cut the assembly. Too bad, it could have been built so that wouldn't be necessary.

I've soldered pipes and electronics, but no pipes bigger than 3/4". But I think I'll be up to the job. I'll put a steel shield between the work and the wall, and have the garden hose and fire extinguisher ready. Thanks for the lead on the banded coupler though.

The store doesn't have 1 1/2" repair couplings. Could I take a dimpled coupling and pound the dimples out? Or what if I grind them down with a Dremel tool?

What do you think of using Oatey #95 Lead-free Tinning Flux? It says: silver solder powder is added to pre-tin the copper pipe, solder temperature range of 400 - 700 degrees F, excellent for large diameter copper.

I expect to use a propane torch and Oatey Safe Flo Silver Lead-free Plumbing Solder (melts 420 F to 460 F).

 

[Reach4]

What do you think of using Oatey #95 Lead-free Tinning Flux?

I liked it a lot. With lead-free solder it worked better than the old stuff did when using the leaded solder.