Basin waste fitting - do I need a washer?

[bemused]

This is my first post here so excuse me if I'm in the wrong place. I'm fitting a small basin in a cloakroom and was given a slotted chrome waste to go with it. Apart from a plug, the only parts are the threaded waste pipe that sits in the basin, and a large flanged nut that secures the waste in place. There is however no large washer to go with the nut. Now I'm not sure if I need one but it doesn't quite feel right to just tighten up the nut against the ceramic without a washer of some sort, and I'm sure it won't be water-tight. So, do I need to get a washer, or do I just add a bead of sealer between the basin and the nut?
Grateful for any advice, thanks.

 

[sonray ltd]

you need a rubber seal washer between the two.
you can use a basin mate which are obtainable from b&q.

 

[bemused]

Many thanks sonray, I got one yesterday and it worked a treat!