Bath waste seal which way up?

[Yanni]

I bought a Mcalpine bath waste and it comes with a rubber seal. One side has two very thin ridges where the other one has 4 thick ridges on it. Which way goes to the bath and which one to the waste?

It feels more natural the thick ridges on the waste face but what do you usually do?

 

[Burnerman]

The multi ribbed side to the bath.....sometimes filled with silicone if you want belt and braces!
John

 

[Madrab]

+1 , just fill the centre ridge with silicone and don't overtighten

 

[Yanni]

So am I filling the multi ridge section with silicone?

 

[Burnerman]

Thats what I do, but as Rob says, don’t overtighten......you don’t want the washer to be squeezed out of place.
John

 

[Madrab]

I only put a small bead around the centre ridge, just enough for it to spread out when it's nipped up and it doesn't side as much I find. Invariably the underside of the bath wastes (acrylic especially) aren't entirely flat and a little silicone just fills in the gaps, some manufacturers do square the base of the waste, others don't.

As John says it's a belt 'n' braces.

 

[Jackrae]

Water can also creep down the bath-waste threads so you need to form a seal between the waste flange and the bath interior surface (to prevent water getting to the threads). Even if a top-side seal is provided, a ring of silicone where the threads meet the flange might be prudent.

 

[shackec]

Just found this post. Very helpful. I have had similar problems with plastic back washers fitted to the pillar of a goose neck kitchen sink. The washers are smooth on one side and have a concentric groove on the other.I have always assumed the grooved side goes towards the side to be sealed but have never seem an instruction to this effect! Thanks