Freezing condensate drain

[Chris J Dixon]

I posted this a few weeks ago, but didn't get much inspiration, so here it is again.

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, to get the best result for least work and expense?

Chris

[Bob Minchin]

As you have found, insulation will not stop things freezing - it will just take longer or if there is other heat input such as more hot condensate or heating tape it might just help. Given that we only get really cold winters from time to time, why not just use the bucket method? This could still in theory freeze up if the drip rate is too low but at least you would see the formation of the icicle. Sensible precautions and observation during cold weather sould be all you need. When you replace the boiler next, get a condensate drain properly routed though the house into the foul drain and don't accept anything less than a proper job.

Bob

[Chris J Dixon]

That just isn't feasible, I can't see that there is a route available.

The soil stack is internal, in the external corner of the kitchen, which has a solid floor, was recently refitted, and I hope will see me out.

Any route from boiler to soil pipe would also cross the back door.

If I were to consider for a moment pumping upwards, the bathroom is above the kitchen, another expensive job I hope never to have to disturb. Joists run across the route, which is covered by the rather large bath, as does the kitchen extractor duct, completely blocking the route.

Chris

[Andrew Gabriel]

Some years ago (before condensing boilers were popular), I plumbed in a dehumidifier, and also had to route the condensate pipe outside. I made up a length of insulated resistance wire, and ran it inside the condensate pipe, poking out the end. It ran from 18V AC, and was switched on by an outside froststat. Worked well for a number of years.