The plastic pipe under my kitchen sink is leaking. This top pipe seems to simply be resting on the bottom section. Is this how it is supposed to be? I can freely pull the pipes apart with a little bit of force... Where can I get more information on this type of joint?

enter image description here

  • One other note - in a home improvement store, the waste pipe fittings are normally grouped together, so you can go and shop for what you need without worrying about sorting though all the other types of pipe. In the US, kitchens normally use 1-1/2" waste pipe, and bathrooms will use 1-1/4", so make sure you get the right size. – JPhi1618 Oct 15 '15 at 14:09

In the UK this would be called a compression waste fitting. There is a rubber ring that goes around the pipe, and is squashed by tightening the nut, in order to achieve a watertight seal.

The pipe should go past the nut, into the fitting, until it stops. This would probably be an inch (25mm) or slightly more.

To fix the joint:

  • Unscrew the nut
  • Remove the pipe
  • Clean the pipe (it looks filthy - this will make it difficult to make it watertight)
  • Check the rubber ring is intact (if not, buy a new one from your local hardware store)
  • Lubricate the ring with detergent or soap (or something similar)
  • Put the ring over the pipe (Note: there should be a chamfer on the ring. This chamfer goes inside the fitting. This picture is the best I could find to show it)
  • Put the pipe inside the fitting (as far as it goes - hopefully the pipe is long enough)
  • Tighten the nut. "Hand-tight" is enough - i.e. don't try too hard to tighten it. if you do you can distort the rubber ring and hence lose water-tightness)

One alternative point: If the water is collecting at this joint, it is not necessarily this joint which is leaking. I once took a joint apart and put it back together three times, trying to make it watertight, before I realised that the joint above was the one leaking, and the water was just collecting at the lower joint.

However, given that you say the pipe comes out of this joint easily, it probably is this joint which is leaking.

  • 1
    Sometimes the rubber ring is made of a silicone or some other compressible substance, rather than actual rubber. – Wayfaring Stranger Oct 22 '15 at 17:20
  • I finally got around to fixing this. The rubber ring is called a reducing washer. – Vivek Maharajh Dec 11 '15 at 16:51
  • Appears "compression waste fittings" are more common in the UK (and possibly some colonies) while slip joints (a different fitting) are more common in the US, FWIW. – rogerdpack Feb 1 '16 at 11:09
  • @rogerdpack - Are they different fittings? From Tester101's answer and a quick google of my own, they appear the same to me. – AndyT Feb 1 '16 at 11:33

That's known as a slip joint. If you remove the slip nut, you should find a beveled washer on the pipe.

To put the joint together, you'll slide the slip nut onto the upper pipe, followed by the beveled washer (bevel side down). Then you'll slip the upper pipe inside the lower pipe, and use the nut to tighten the joint.

Looks like it's a waste tee similar to this.

waste tee

The trap should be attached to the bottom of this piece, probably using another slip joint.

When tightening this type of joint, you want to be careful not to overtightened. Hand tight is usually all it takes. It should be just tight enough, so that the pipes don't easily come apart.


The fitting in the photo is called a "T"fitting. It looks to be a 1 1/2 inch diameter pipe (as opposed to a 1 1/4 inch). It is made from PVC (polyvinyl chloride). It also is used for a double sink when two drains are needed. Hence the "t" shape. If not connected correctly they will become loosened. The top section should penetrate the lower for at least 1-2 inches. Also, check the washer is not split. Unscrew the nut and lift it up. Under it is a plastic washer, make sure it is not broke. Push the top or lift the lower sections and re fasten the nut hand tight. Run the water and check for leaks.

  • 2
    It's likely part of a p-trap, but the actual connection, itself, it not a p-trap. – DA01 Oct 15 '15 at 5:22

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