I had a similar problem years ago. 1935 house, modern kitchen sink, draining
out trough wall to 3" cast iron waste outside. Sudden change from horizontal
to vertical at a regular (not swept) bend was inclined to clog. I replaced
with a swept Tee. The "swept" route carries flow, the unused leg is closed
by a stop-end plug. All push-fit by the way. Like your option (2). Access is
easy by prising off stop-end. Never had to do it since. I think the "swept",
has probably cured problem.

--
OlavM
Overlooking the Clyde where it meets the Sea
"Chris J Dixon" wrote in message
...
My boiler is in the integral garage, and the condensate drain was
taken through the wall, vertically down for a short distance to
join with an existing 32 mm pipe, the drain from a sink. This
then runs at a shallow angle for about 3 metres, where it joins
into the rainwater downpipe, eventually discharging into a
soakaway. (I didn't fit the sink, I know it is not really
correct.)

As I had freezing problems, last year I lagged the external
pipework with 25 mm thickness Armaflex. The extreme weather last
winter still caused me some problems, at the junction with the
downpipe. Luckily, I was able to thaw it relatively easily, and
then kept the pipe clear by periodically running water from the
sink to prevent any ice accumulation.

There are no possible alternative drainage points.

Since, by its nature, the downpipe will be open to air, I don't
see much point in trying to get sheet insulation around the
junction point.

(1) I could consider routing the solvent-weld drain internally
through the garage, to reduce the exposure, but it would be a
fiddly run, and the junction point issue still arises.

(2) In addition to (1), I could, adapting a recent suggestion in
a different context, use a swept-tee in place of a 90 degree
bend, and insert a solvent weld screw-cap end in the "unused" leg
of the tee, just before it passes through the wall. When it
freezes, I could remove the cap and allow it to drain into a
bucket. This is fine so long as it doesn't have to be left
unattended.

(3) I could use trace heating, either with the installation as it
is, or having modified as (1) above. I guess this still requires
me to lag the heated area, with hand-crafted chunks of expensive
Armaflex.

Any thoughts and experiences on the best way to proceed, for
greatest cost/benefit?

Chris
--
Chris J Dixon Nottingham UK


Have dancing shoes, will ceilidh.