I am ready to cut the drain pipe behind the wall with the 12" ruler laying on it (see pics) and raise the height of the vanity's sink drain, but I'm not sure the best way to do this. I want to raise the drain pipe about 6 to 7 inches. My ideas so far, but it seems like I'm missing an easier solution:

1) Cut the drain pipe above and below the vanity downspout and reconnect it 6 inches higher (so I would reuse the horizontal drain pipe and connect it to the vertical one 6 inches higher, cut a new hole in the drywall 6" higher and call it done.

2) Cut the drain pipe just before it enters the wall connect it 90 degrees up the 5 inches and 90 degrees toward the wall?

3) Cut the drain pipe and connect a 45 degree up so it connects with the wall about 5 inches higher and connect a 90 towards the wall.

I'm not sure how to connect to that pipe.. (Is it stainless galvanized steel?) Also not sure how to connect it.. I think I need a rubber collar with 2 stainless steel clamps. Advice appreciated. I normally just research these on my own, but am pressed for time to get this done. Thanks in advance.

The wall drain connection is about 4 inches too low That's a 12 inch steel ruler laying on the pipe. Where should I cut this and will a sawz-all with a metal blade cut it?

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You might have just enough height there to use an S trap and connect the downward section to the right angle piece once inverted.

  • It seems like it would drain very slowly if I do double S traps and be nearly impossible to snake... – Dan B Aug 21 '19 at 21:13
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    It would be more difficult to snake, but with these screw together fittings I find it easier to just separate them and clean them out. Shouldn't affect flow any. – Phil G Aug 21 '19 at 22:16
  • I'll give it a shot. It will be much harder if I compromise the galvanized and end up having to replace the entire backside... That is definitively not in the budget! Thanks for your post. – Dan B Aug 23 '19 at 18:35
  • I got some PVC and dry fit it and I think it should do the trick, but my pipe coming out of the wall is rusty and I can only get about 3 revolutions on my PVC fitting... Should I clean the male galvanized threads coming out of the wall and if so is there a good way to clean those threads? @Phil G – Dan B Aug 25 '19 at 3:13
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    How was the 90 degree section attached to the galvanized? There should have been an adapter from the FIP thread to the PVC compression fitting that wouldn't have needed to be disturbed, but it's not visible on the first photo. If not, then you need one, I don't think the PVC and FIP threads are the same. There are thread files you can use to clean up the FIP, – Phil G Aug 26 '19 at 13:31

Adding a 45 to offset at the galvanized nipple and extending so a trap will fit is the right thing to do. but do not raise the back side plumbing extend the tail of the sink. A straight shot down will flow better and have less bends to build up and create clogs. Even though I have all my threading gear I try to stay away from messing with old metal drains. There have been a couple of times on my own property I have started on a small job and ended up with all new lines to the septic tank. Putting in the 45 will take a little more room under the sink but it will be easier and less risk of opening a can of worms if the 40+ year old drain line crumbles. In my case it was a 1960’s home and even the cast main line was compromised. my guess that one of the prior owners had used a harsh drain cleaner regularly (this was back in late 90- early 2000 so that plumbing was only ~40 years old I haven’t seen new galvanized used since the early 70’s except in rare cases). So if you have metal it could be very fragile.

  • It's not really clear what you're suggesting, Ed. Maybe revise to be more specific where this offset would go. Are you suggesting a longer tail and work behind the wall? Does the wall penetration height change? – isherwood Aug 21 '19 at 13:58
  • Thanks @Ed. The metal on the horizontal part of the backside seems very solid.. I'm not sure bout the vertical downspout. I just had a thought - can I put the trap on the backside, which would allow me more room under the sink? Besides this being unconventional, is this against plumbing code or does it logistically not make sense? – Dan B Aug 21 '19 at 14:04
  • diy.stackexchange.com/a/81740/40151 - Seems OK esp as it is accessible from the backside to have the trap in the wall... I really like that idea.. Let me know if there has been any change in the code. Secondary question @Ed Beal, can I cut and connect PVC to that steel? if so, what's the best way to do it? – Dan B Aug 21 '19 at 14:09
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    I meant to add the 45 to the galvanized & Extend at the lower level wasting cabinet room. The home I referenced the plumbing looked great I was doing the same updating a bathroom sink, the pipe collapsed when I tried to remove the nipple, when trying to replace the 90 the next section split at that point I could see all the horizontal pieces were in really bad shape, the cast main line actually had holes in the bottom but the clay soil had sealed it so be careful I did not plan on re-plumbing that entire drain it looked good from the outside. You can put the trap on the other side of the wall. – Ed Beal Aug 21 '19 at 14:21
  • Thanks for all the imput. This was a good solution also, but I opted for the sideways S using 1 1/2" PVC which is rock solid and my wife loves both the look. I like that we can fill the cabinet and not have to worry if something bumps into it as it is so solid. I have used the crap polypropylene in the past and the quality, solidness, and ease of installation of the PVC is amazing. I used to dread a leaking sink. No more. – Dan B Aug 27 '19 at 6:16

Just incase anyone else comes up against this, I thought I would post my final solution with 1 1/2" PVC which worked like a dream and (despite my concerns) flows like a river: Half Inch PVC with sideways S.. thanks to the pros above for the assist!

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