Richard Savage wrote:
SNIP


Does anything else empty into this drain?

Reason I ask is that the U bend in the gulley that serves our kitchen
sink collect a fatty deposit at the top of the outlet side of the U
bend exactly as shown in your txt drawing.

Now, my office has had some very serious drain lining activity taking
place for the last few months and, being nosey, I have been chatting
to the blokes doing the work. I mentioned the U bend problem and
asked what I should use to clear it - mentioning that I used Caustic
Soda solution with apparent success.

Apart from agreeing that Caustic Soda is a good, if not better, than
any of the clever products they asked if either a washing machine or
dishwasher used the same gulley. The reason being that the soap from
these machines can build up in a fat-like deposit - remember that
saponified fat is soap - which isn't carried away in the rinse water
away because of the low wash temperatures. Our dishwasher shares the
same gulley. QED.

The point being that it might not be cooking fat that is blocking the
U bend. And it will have to be done regularly - or you can increase
your wash temperature

That is an excellent point. Same situation we have. Hmmmm.



--
Dave - The Medway Handyman
www.medwayhandyman.co.uk