On Thu, 9 Jul 2009 07:01:12 -0700 (PDT) someone who may be
lardconcepts wrote this:-

"The entire pipe run will be sealed, so no trap needed inside."

Isn't this likely to cause siphoning?

No, the pipe will be draining into a gulley-style drain, so as there's
an air gap between the two, there's nothing to siphon.

Imagine the situation where the machine has just pumped out the last
water. There is now a pipe full of water propelled by the pump down
a "good fall".

Depending on the arrangements inside the machine one of two things
is likely to happen. If you are lucky the water will draw air into
the pipe behind it, drawing the air through the pump. This will
empty any trap in the machine.

If you are unlucky the water will not be able to draw air behind it
and will not be able to draw air along the top of the pipe (as it
would be able to do with a larger pipe). In this case your pipe will
be flattened by atmospheric pressure on the outside of the pipe.

Either find out what is inside the dishwasher, or arrange an air
admittance valve where the end of the hose and the start of the
fixed pipe starts. Do make the long run in proper pipe, suitably
supported and with easy bends if there are any (to minimise back
pressure), I would use copper pipe.

Done properly there should be no problem even with decades of use.



--
David Hansen, Edinburgh
I will *always* explain revoked encryption keys, unless RIP prevents me
http://www.opsi.gov.uk/acts/acts2000/00023--e.htm#54