Plumbing question

My PVC plumbing under the kitchen sink decided to start leaking at one of the connections. I took it apart and reassembled a couple different times (replacing the O-ring with a new one), but still I get no joy.

I thought it was fixed the first time, ran the water and everything seemed fine. But when I started the dishwasher that same connection failed.

I figured I’d just replace the entire J section, so off I went to The Home Depot.

The worker there was very helpful. I described the problem and the setup, and he said I had connected it incorrectly. As he described it, the outlet from the garbage disposal should be positioned above the drain outlet. Water runs downhill, said he. Made sense to me. I left without purchasing anything.

When I get home, though, I look at my plumbing and realize that what he said would be impossible to accomplish with my setup. My disposal outlet is actually about an inch below where the water ultimately exits the under-sink cabinet.

To accomplish what the HD man suggested, I would have to raise the sink/disposal (not an option) or do a major overhaul of the nearby plumbing.

Thing is, we’ve been in this house >20 years and living with that setup. All of a sudden I can’t get the connection to not leak.

(although right now, it seems intact but I think it’s pretty fragile; haven’t tried running the dishwasher again).

Any thoughts?

Got a photo?

Sch 40 ABS … the stuff that glues together … that PCV slip-joint crap is just crap …

Without being able to see exactly what you’re talking about, it does seem like the disposal drain is too low. If that drain is below the exit you’ll have standing water in the disposal drain. My disposal comes in just above the J trap. As far as how to fix the problem… sounds like a job for a professional plumber.

Every time we have leaking with the twist on connectors, it’s been because they were too tight. Now I screw together the drain lines, barely hand tight, then tighten a little bit at a time until we don’t have leaks. When my husband puts them together always over tightens.

If this set up has worked for you for 20 years, I don’t think the configuration is the problem.

Sounds like I didn’t do a great job explaining the layout.

The sink drains directly downward into the disposal.
The outlet from the disposal (let’s call it outlet A) runs horizontal for an inch, then straight down vertically into the J trap.
The waste water, heading downward, does the U-Turn in the J, ascends, then turns 90 degrees and connects to a horizontal piece of pipe that exits the back of the under-sink cabinet (outlet B)

Now, outlet A is maybe 10 inches above the floor.
Outlet B is maybe 11 inches above the floor.

The Home Depot guy said that joint will never *not *leak because of this configuration (outlet B being higher than outlet A)

(and again, it hadn’t leaked for the past 20 years)

I will post a photo soon-ish.

Thanks for the replies,

Here is a link to the photo:


First of all, which joint is it leaking from?

Secondly, I’m really, really surprised that you haven’t wrecked your disposer. That configuration means the disposer is always full of water, which is just asking for trouble.

Nailed it … no truer words have ever been posted here on SDMB …

The drain pipe in the wall is too high … the garbage disposal was put in at a later time … I’d guess if you took out the disposal unit and just put the regular drain piping in; it would fit like a champ …

Not if you know how to assemble it properly. A lot of people don’t. If you use ABS and then change disposal, sink or many other changes ABS does not unglue and has to be ripped out.

Just looked at your picture. You have a problem there. You may need to lower the drain outlet. This may take a plumber.

Yup … ten or twenty dollars worth of fittings and a couple hours labor …

Compare to an unnoticed slip-joint leak after a few years … how expensive is it to replace everything including the sub-floor?

The bottom left fitting is the leaker.

FWIW, the disposal is not always full of water.

Looks that way to me, too. I don’t see how all of the water in the disposer can drain.
The outlet is too low, and the slip-joint connections may not contain all the water that must be present.

Even if I got the joints to stop leaking, I wouldn’t be able to trust them to not start leaking again.

This shouldn’t be too hard to fix properly. If you cut the back of the cabinet hole down a few inches and expose the drain pipe lower, you could cut the pipe and install a new elbow.

How important is having a garbage disposal to you? Another option is to ditch it and then your drain plumbing becomes so much easier … I, myself, wouldn’t use one even if I had it installed … I compost my food wastes, and that’s rarely very much in the first place …

Automatic dish washer is another thing I would never use … even when I had five teen-age children living at home … I’ve never found it saves much time at all … but that may be because I’m such an awesome and gifted hand washer … [smile] …


You mean a tee … there’s also a pipe going up and through the roof for venting … although I agree anyone with a little experience should be able to do this … it’s not that hard but it’s not a thing I would recommend to a complete beginner … assuming it’s ABS and not cast iron piping behind the wall …

Only until you have to replace the drain line because of a change in the kitchen. Never had to replace any sub flooring because of a drain problem. Only time I had to repair a cabinet was when someone did not know how to connect and check a drain line after 40+ years working.

Picture won’t open for me. But I suspect that the ‘O-ring’ is actually a beveled nylon bushing and that you have it in backwards.

aybe, but you need to use the slip-joints in places (like under the kitchen sink) where you might have to clean out the trap, or even add a disposal or replace the faucets over the years. You need to be able to undo connections remove the pipes on occasion. Unless you are willing to just tear it all out & replace it every time!

Well, either you’ve been lucky, just haven’t taken those kinds of jobs or no one thought to approach you with such a job …

I’ve always returned my bids with “line items” like this for kitchen/bathroom remodels … if we’re rotten to the beams, it will cost this much, if it’s just sub-floor, then this much … if it’s only the under-layment, then here … if I tear out the cabinets, fixtures and drywall and all the structural elements are fine … then I cross out all the extra line items … and then it looks like I saved the customer a little bit of money …

Because we both know stubbing beams and replacing sub-floor is a half day’s labor … compared to a full week finishing the drywall … and if you’ve priced cabinet lately, then you also know replacing all the structural elements is but a bit a fog in the eye of a hurricane … gees-my-knees Christmas …