I’ve purchased a new bathroom sink faucet on Amazon, and I’ve installed the set. But I’m puzzled by a rubber ring near the bottom of the drain body that came with the set. I couldn’t figure out what it’s made for. The second picture shows that I’ve removed it (did not install). Does anybody know what it does?
- Ring labeled "A":
Multi-function tapered rubber gasket that centers the drain assembly in the bottom sink hole, cushions the clamping action of the nut that secures the drain assembly, and seals the lower hole (most sinks have an overflow drain-hole and channel cast into the body of the sink that leads to the space between the upper main drain-hole and the lower main drain-hole, overflow liquid enters the drain assembly through small holes in the drain assembly within that space).
- Ring labeled "B":
This is a plastic (sometimes metal or fiber) friction ring; contradicting it's name, it prevents friction between the nut and the rubber gasket above so you can firmly tighten the nut without the nut grabbing and twisting/turning the rubber gasket.
Perhaps the O-ring provides a seal in some other kind of drain system in another country. I've never seen one like it on a drain tube. If the white compression nut shown has a wedge shaped compression washer under it, that's all you need and the O ring isn't part of the seal. In any event it can't do anything because your drain tube is too short! It barely makes it into the trap. Hopefully if you do have a proper compression washer under the nut, it has enough tube to do its job, otherwise you should buy an extension.