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So we're remodeling our kitchen and my wife insisted we get a new farmhouse sink. We had a contractor install the new sink and after getting it put in he mentioned that the disposal line is about the same height as the drain line in the wall. Maybe the disposal line is higher than the wall line, but if it is its like millimeters higher.

He connected it up using some of those flexible tubes and said we should be good. I was a little worried about this set up, so I tested it by pouring about 3 gallons of water from a bucket (we don't have a faucet yet) down the drain and then unscrewed the black tube line from the disposal. Water was sitting in the p-trap all the way up to the top of the this black tube, but was not in the disposer itself. I'm afraid that will be a problem once the disposer starts getting used again.

I was googling around and most suggestions are to either 1. Get a shallower sink (won't happen, wife won't allow it). 2. Remove the disposal (I use it every so often so I'd prefer not to do this if I can avoid it). 3. Move the drain line in the wall down (requires plumber because I ain't doing that haha). 4. IF THIS IS EVEN EXISTS, find a disposer with a shorter neck/flange. My current disposer is a Waste Master SS2600. Its probably 19-20 years old and original to the house, but still works fine.

Or is it actually ok the way it is set up like the contractor said? I've never actually explored a p-trap before, but I know they're supposed to hold some water. Is it ok if they're completely full up to the top of the black tube from the disposer?

If its not ok, it seems my only option is #3 or #4. Based on experience what would be the average cost of moving a drain pipe down like 2-3 inches? Like no more than $500, surely?

I've attached some screenshots of the setup.

Water up to top of black pipe

DrainPic1

DisposerPic1

Update:

We'll the new disposal isn't much higher. MAYBE half an inch. Also the ptrap is now too close to the wall so I have to have it come off the side and have an extra elbow in there.

height of wall pipe

height of disposer pipe

new elbow pipe

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    I don't know about the height issue. But you do NOT want that accordion pipe. Replace it with appropriately sized regular pipe. Sep 8, 2022 at 14:28
  • See also diy.stackexchange.com/questions/81969/…
    – P2000
    Sep 8, 2022 at 14:31
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    A small, shallow sink bowl just for the disposer is pretty common, as an accessory to, not a replacement for, the main sink. Presumably you're a non-composting household and on sewer, not septic (if you are on septic, removing the disposal is highly advised...) Accordion pipe is an evil kludge that should be a code violation, but apparently isn't. It will clog, or break, or both. Particularly with the material a disposer will send through it.
    – Ecnerwal
    Sep 8, 2022 at 14:44

2 Answers 2

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Normally, there wouldn't be water all the way up to the 90° going into the disposal, however, that isn't inherently an issue. (You're not removing that pipe in daily operation, right?) So long as you don't have water standing in the disposal, you should be fine.

I'd agree with the comments that the much bigger issue is the accordion pipe. They're just not recommended.

When replacing that accordion pipe, simply raise the whole trap up 1/4-1/2" so that there is some slope from the top of the trap to the stub-out on the wall to ensure you've got good drainage.

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  • Thanks, I've got a plumber coming in 11 days to take a look at it. I just don't trust myself with this stuff. I'll ask if he can replace the accordion pipe. If it ends up not being too costly I may just have him lower the drain pipe in the wall as well. If worse comes to worse I guess I'll just ditch the disposal, use regular pipe to the wall, and throw scraps in the trash from now on. Sep 8, 2022 at 16:39
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    I actually found a compact disposer whose drain pipe sits a whole inch higher than the one I currently have. I'm going to replace the old disposer with this new one (the old is close to twenty years old anyway). I believe if I then trim the new disposer drain pipe by an inch or so I can align the trap to the wall in almost the same position it was before the new sink was installed. Sep 9, 2022 at 15:03
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    Sounds good, @Fettster777! I'm glad you were able to find that. Having the disposal drain above the wall stub out will definitely help. I'd suggest test-fitting prior to doing any trimming - you might not need to trim.
    – FreeMan
    Sep 9, 2022 at 15:06
  • I added some new pics if you've got an opinion on them. Installed new disposal, but had to make a change with the pipes Sep 11, 2022 at 21:02
  • Based on that last pic, about all you've done is change the shape of the trap. Water will sit between the last elbow (closest to the wall) and the disposal. Again, I don't think this is an inherent problem, but the mass of food that is ground up in the disposal will tend to want to sit in the trap anyway, and then it's got to make that extra journey uphill through another elbow. This will, I believe, tend to lead to more clogging. Be sure to run a lot of water every time you use the disposal and expect to have to clean out the trap pretty regularly.
    – FreeMan
    Sep 12, 2022 at 12:24
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It should be ok as long as your trap arm has the correct slope and is within the critical trap arm length to prevent siphon.

The accordion style p-traps as others have noted aren't recommended and would likely fail code.

Having the water that high does make servicing harder but it is difficult to lower the roughed in stub for the trap arm without removing cabinets and cutting drywall.

https://www.jlconline.com/how-to/plumbing/maximum-length-for-fixture-drains_o

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  • I think siphoning is indeed the big question here due to slope and accordion, not puddling, since we can't see in the wall. OP could perform repeated tests, draining a full basin several times and confirming that every time there is water in the P trap.
    – P2000
    Sep 8, 2022 at 16:39

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