Basin Waste fitting

I need to change my basin waste fitting. It has the rubber gasket so when fitting new one, do I need to put any sealant or just have the rubber gasket compressed on the basin side should be enough?

You need one of these:

https://www.toolstation.com/basin-m...MI_7Xxjd2o6AIViLPtCh32PASkEAQYASABEgLFofD_BwE

Andy

Nope, you either need to seal on the underside or use a basinmate or similar otherwise it will leak.

If you are using a sealant then you will need to fill the gap that you will see between the threaded shank of the basin waste fitting and the throat/opening of the waste hole in the basin. Not too much otherwise you can block the slots for the overflow.

So the black rubber gasket is to seal it from the basin itself, but the basin mate or use of plumbers mait is to go from underneath before the plastic nut to prevent water leaking from the overflow channel right?

Kind of ..... if you look at a slotted metal waste, the slots in the waste will allow the overflow water that will run from the slot cast into the throat of the basin waste but it will also allow the water draining normally from the basin to run down the gap between the basin and the metal walls of the waste. Therefore there needs to be a seal blocking that gap and around the threads on the metal waste, when the but nut is tightened. That can be done by either a basin mate or by the thicker (sometime concave) washer that will be supplied with the waste and using some silicone.

The internal soft (sometimes white) rubber seal that's designed to sit on the inside slopes of the basin's waste hole and the flange of the metal waste only stops the water leaching away when the basin plug is in/closed.

Use a Basin Mate, one time fit and forget solution, never yet had one leak. Old method of Plumbers Mait and washers used to be a nightmare in comparison.