What ho one and all,

Fitting a replacement wash basin; annoyingly, it is a few mm smaller that the one I have removed so will require some silicone 'remodelling' to fill the gaps. But that is s different issue.

Am using the original pop-up waste fitting as the visible part inside the basin is in good condition.

However, the squidgy washer/sealer is not the same profile as the basin is 'slightly' different from the original.

First question; what is this (red arrow) washer / sealer / gasket/ actually called and can one usually buy a replacement?

Second question, in searching Dr Google for an answer to the above, I found one site that suggests using silicone on the green arrowed areas. None of my basins have silicone in these areas; is this something that I should do?

Thanks

The white washer can be replaced by silicone, the black washer best without anything. Tiny smear of silicone if you must

Crucially the thread needs to be sealed with silicone or PTFE and silicone

With the rust on that, I'd definitely be fitting a new one with a new rubber seal. Using old gear is a false economy IMHO.

Had to replace a shower and bath waste last week.

Silicone the rubber to the metal/plastic fitting. Used Plumbers Mate (for the first time) thin smear between the rubber and the bath/shower/sink. Worked like a charm.

I recently refitted an old Victorian(esque) wall hung sink. New waste and taps. Went for plumbers mait . Above and below the top and bottom sealing washer and around threads. Silicone is great, until it's not, or it needs to be removed. No leaks so far. Used same on a shower waste too. It probably doesn't matter that much what you end up using. Could even probably get it to seal dry, with PTFE on the threads. Definitely get a new one though, for the cost of it.

To kinda close this topic, I did buy a Thomas Dudley thing, only to find that the height of the cone is such that when pushed onto the threaded internal pipe, there is no thread protruding from the bottom to screw the locking collar.

Reduced the height of the cone with a scalpel so that it is only around 4mm high, fitted that to the inner threaded part, plus the original rubber washer, and screwed it up tightly. Not a drop of water, unlike the first basin where I replaced the plug and it took some time to get a water tight seal.

Thanks for the suggestion.