Silicone on new sink strainer waste?

[Mathew Newton]

I've got a new stainless steel Franke sink and waste, which came supplied with sealing washers top and bottom. The instructions make no mention of using any silicone in addition to the washers but should I for belt and braces?

[newshound]

I'd expect Franke to have well finished parts and good quality seals and screwing bits, in which case you should not need silicone.

[Dave Liquorice]

What are the washers made of and how soft are they? If they are some form of thin (1 mm ish) soft rubber they'll do the job "dry" and without needing to be murdered up. If they are fairly regid plastic they'll probably need a sealant but I wouldn't use silicone, just plumbers mait.

I'm also loath to use a washer on the top between the waste flange and sink as the washer thickess can create a ridge that holds water/muck. Really depends how well the flange matches and sits in the sink. Without a washer I'd seal with plumbers mait.

[ss]

..... +1....before I would use silicone.

[PeterC]

ISTR some mention of Plumbers Mait prone to 'growing' things and an alternative to it - is there such a thing? Also, PM is a bit awkward as it tends to stick to the wrong item (me!) and is difficult to get off - the trick of rolling some of it works only to some extent.

[Dave Liquorice]

I'd expect decent stuff from Franke as well but a good brand name doesn't always mean good quality goods these days. B-(

[newshound]

I've also occasionally used Boss White in this sort of application, more runny than PM and easier to clean off "cleanly". But typically on cheap and nasty waste fittings.

[Mathew Newton]

I must admit everything does feel like it is good quality, and whilst I do tend to do belt and braces (read: over engineer everything) my gut feeling it it really isn't necessary on this occasion. I could always dry-fit and only deviate if the need arises.

[Mathew Newton]

The underneath one is soft rubber, and fits/moulds well with the underneath parts and is ridged to presumably seal well with the sink. The upper one is a thin foam; probably ~1mm as you say.

I've tried with and without the foam washer and I think I'm leaning towards it being better with. There's quite a recess in the sink and so it doesn't sit proud, and if anything it seems to be helping it self-centre.

As I mentioned to newshound I think I'm going to go for dry fit and only go for silicone/PM should the need arise.

[Mathew Newton]

I should've uploaded a picture really as thinking about this it has dawned on me that not all sink wastes are the same.

Here's what I've got:

With the above-sink parts consisting only of a pressed plate (i.e. there's no threaded column that protrudes through the sink hole) it's clear that the watertight seal is actually a function of the rubber washer *underneath* the sink. If I was going to be putting silicone/PM anywhere that's where I'd be needing to put it but given the ridges on the washer I don't think it'll be required.

[Mike Clarke]

I fitted something very similar to a couple of Ikea sinks 11 years ago without using any sealant and haven't had any leaks.

[Peter Burke]

Mathew Newton [e-mail] wrote in news: [e-mail]:

I would probably do the thin top washer but not the compliant bottom one, not with silicone but with one of the uber sticky sealants like Stixall, just a smear, nothing more.

I would definitely do the overflow however they are very much prone to leak and again with stixall. Best use clear or black, white can discolour.

Excess can be wiped off with a paper towel moistened with isopropyl alcohol.