On Thursday, 25 August 2016 18:41:46 UTC+1, John Rumm wrote:
On 25/08/2016 12:21, tabbypurr wrote:

Vaillant condensate circuit information:

It is not necessary to provide air breaks or extra traps
in the discharge pipe as there is already a 75mm high
trap inside the boiler. Fitting an extra trap may cause
the boiler siphon to work incorrectly.

(b) Connecting into the internal discharge branch
(e.g. sink waste or washing machine) with an external
termination, the condensate drain pipe should have a
minimum diameter of 22mm with no length restriction
and should incorporate a trap with a 75mm (3)
seal. The connection should preferably made down
stream of the sink waste trap, if the connection is
only possible up stream, then an air break is needed
between the two traps. This is normally provided by
the sink waste.

Don't those two contradict each other?

Not quite (although it could have been worded better)! What they are
seeking to avoid is having the condensate drain connected directly to a
second trap without any air break. So into an open waste pipe before a
trap is fine, and into a waste pipe that is open at the far end but
after a trap is also ok.

(I find that a washing machine stand pipe waste is often a handy place
to take a condensate drain - but a tee on the top and a reducing bush to
take the 22mm pipe, then the side branch can be left open for the hose
from the washing machine etc)

ahh, makes sense Cheers.


NT