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I'm a newcomer to household plumbing and particularly have problems with the correct names for fittings etc.

We have a leaky cloakroom handbasin. Directly on the basin outflow the ceramic is connected to the U-bend piece with a tatty rubber ring and whatever bit of pipe partly sealed with something like gritty cement of some kind. This has cracked and begun to leak a lot. Fairly sure the plumber didn't want to spring for the correct parts.

I'm thinking there should be a proper fitting to connect the basin to the U-bend, even if the basin turns out to be a non-standard size (it's very small). Perhaps something funnel shaped? I don't know.

What I need to know, before I can order anything, is what this fitting would be called and how would I go about measuring the basin and U-bend fittings for the correct sizes.

By the way, I'm in the UK and the house was built c. WWII.

enter image description here

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    There's a good comprehensive answer from FreeMan below. In addition: At least in the US the vertical plastic pipe coming out of the bottom of the sink is called a tailpiece and the U shaped assembly is called a P trap. Also, make sure that the tailpiece and the P trap are vertically aligned. In the photo it appears that the alignment may be slightly askew. This can cause leakage from the basin.
    – HoneyDo
    Feb 13, 2023 at 16:45
  • I would argue, @HoneyDo, that the "tailpiece" is the threaded part of the strainer installed in the drain and that the first white section is a "tailpiece extension", but that's just picking minor nits and I'd agree in principle on both terminology and making sure the pipes line up.
    – FreeMan
    Feb 13, 2023 at 17:35
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    @FreeMan - You could argue that, but it isn't necessarily factual. The part you refer to as the "tailpiece" is often called the drain fitting and the tailpiece attaches to it. I've seen it both ways. But potatoes, potahtoes - right? I gave you a +1 for a good answer.
    – HoneyDo
    Feb 14, 2023 at 5:01
  • Tomato, Tomahtoe to you, then @HoneyDo. #NotAPlumber. ;)
    – FreeMan
    Feb 14, 2023 at 12:43

1 Answer 1

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The only unusual thing I see on the bottom of your sink is how the drain itself seems to be cast into the bottom of the basin. The bottom of the basin is commonly reasonably flat so that the sink strainer will screw up nice and tight to it.

The "leaking cement" appears to be some sort of sealant someone else applied in an effort to seal up the leak that you are now trying to fix properly. It shouldn't have been there in the first place and it's very unlikely that it's "leaking" from anywhere.

It's hard to be certain without a picture of the inside of the sink, but most likely I think you need to:

  • Unscrew the trap. This would be the three big, knurled knobs on the "u-bend" under the sink identified by the red arrows
    • Screw together traps are very common and are actually preferable to glue-together ones because you can easily take them apart for maintenance
    • Leave the fitting attached at the wall.
    • Clean out the gloop (if any) in the trap by pushing/scraping/washing it out. (Use a different sink if you choose to wash it up!)
  • Unscrew the sink strainer from the sink itself.
    • You'll need a large wrench of some sort to grab the flats on the black plastic nut that holds it against the bottom of the sink. (The green arrow)
    • It would be preferable that the wrench not have any grippy teeth on the jaws, as they're likely to just chew up the plastic. Smooth, flat jaws are better here. If all you have is something with teeth, use care to not chew up the nut too much.
    • I believe your tatty rubber washer is between the sink and the nut you'll need to remove. (The blue arrow).

enter image description here

  • Take the strainer to your local home improvement store and/or plumber's supply store to look for an equivalent.
    • It might be unusually shaped because of the shape of the basin.
    • In the US, the output side would most likely be 1-1/4" pipe (~31mm in UK), but I don't know your standard pipe sizes. It's likely that this is a standard pipe size. Having the old part in hand will allow you to compare, to be sure.
  • Install the new strainer according to the manufacturer's instructions.
    • Usually, you'll need plumber's putty on the inside of the sink between the basin itself and the bottom of the new strainer.
    • You'll put the washer(s) of the new strainer on in the proper order (some come with a rubber & cardboard washer, use both if provided).
    • Tighten the new nut (comes with the strainer) according to instructions. Usually hand tight plus 1/4 to 1/2 turn with a wrench.
    • As before, if you use a wrench, you'll want to use smooth jawed ones or great care to not chew up the nut with a toothed-jaw wrench.
    • Clean out the squeezed out plumber's putty up top using your finger to get the excess removed.
  • Reinstall the existing plastic trap parts.
    • Use NO plumber's putty or thread tape! These are designed to seal properly with the internal plastic or rubber gaskets.
    • If the gaskets look pretty grotty, too, you can pick up a set of new ones for only a few £$€. Make sure you reinstall the new ones with the same orientation as the old ones - they usually have a flat side & an angled side and won't work if installed backwards.
    • These usually only require hand tightening to be leakproof. If absolutely necessary, use a wrench to tighten an extra 1/4 turn or so, but generally not more than a 1/2 turn. Too tight and you'll deform the thin plastic and cause more leaks than you'll solve.
    • If you want to spruce up the appearance a bit, you could replace the entire trap with a chromed plastic or even brass/copper trap. These will also screw together. They provide no benefit over the white plastic one you have other than a nicer appearance.
    • From here, there doesn't appear to me to be anything wrong with the trap assembly itself other than that it's a bit dirty on the outside. If it truly offends you, you could replace it with another white plastic one, but again, that's a purely cosmetic choice - I just don't see justification unless it's obviously damaged when you take it apart.
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    Thanks for the thorough answer. I'll dismantle everything tomorrow, scrub them up and see if I can find a replacement. Hopefully I won't hit any snags. I may be back. Feb 13, 2023 at 18:15
  • You're most welcome. If you run into another issue, it would probably be best to ask a whole new question unless you're just seeking some clarity on this answer.
    – FreeMan
    Feb 13, 2023 at 18:19

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