On Mon, 19 Jan 2009 20:27:36 +0000, The Medway Handyman wrote:

Looked at a job for a local church on the way home. The 'committee'
were present.

A parishioner has given them a load of kitchen units only a few years
old and they want me to rip out the tatty old units in the hall & fit
the newish ones.

A plan was produced. Sink to remain where it was on the left end of the
wall, built in oven & hob on the right of it.

Obvious problem, the waste from the sink runs through the units & along
the length of the wall around 2' above the floor & enters a soil pipe -
due to various other fittings it couldn't be fitted lower down. The
oven goes right to the back of the unit.

I explained this & suggested we move the sink to the other end, next to
the soil pipe. No, they didn't want that, it would cause havoc with the
tea making.

One old boy came up with a 'solution'. Put several elbows in the waste
pipe, to take it down to floor level, under the unit, back up the other
side & reconnect to the waste - effectively forming a huge 'U' in the
waste pipe.

I tried to explain that it wouldn't work, the huge 'U' would always be
full of water & the sink wouldn't empty properly.

He was adamant that it would work. I'm start to doubt my own sanity
here.

Surely it wouldn't work?

As per all the other answers, it would work, as long as it's sealed. And
it would block easily in that situation too.

Here's somewhere else it was used, on a somewhat larger scale:

http://www.romanaqueducts.info/siphons/siphons.htm