DIYbanter - View Single Post

In article om,
writes:

Thanks. Why would I need a trap teeing into the 110mm grey stack pipe
when I don't need one teeing into any other drain pipe?

All connections to a soil stack need a trap.
However, there's very likely to be one in the boiler anyway,
as it's also required to stop the flue gasses leaving the
boiler via the condensate pipe. You might want to include
an air admitance valve in the pipework though, so that no
pressure changes in the drain can suck the boiler's trap dry.

Also would suggest not routing the 22mm pipework outdoors.
My boiler requires any outdoor condensate pipework to be at
least 32mm, to reduce chance it will block with ice in cold
temperatures.

--
Andrew Gabriel