Proper fix for icing-up condensate pipe

Ectophile

I have a condensing gas boiler.  Unfortunately, the routing of the condensate pipe isn't ideal.  It pops out through the outside wall of the house at first floor level, then runs all the way across the back of the house, before dropping down to the drain.  I have wrapped it in lagging, but with such a long run, that doesn't really solve the problem.

Whenever the temperature drops below freezing, an icicle forms at the end of the pipe.  It gradually grows until it fills the width of the pipe, then the water in the pipe starts freezing.  I have been tipping hot water over the end of the pipe several times a day, but this evening, the boiler started making ominous gurgling noises.  So it was clear the pipe was totally blocked.

The pipe had an L-shaped end on it, to direct the condensate into the drain.  The drainpipe is in the way, preventing a nice vertical run straight into the drain.  Unfortunately, that same L-shaped bit tended to trap any ice inside the pipe even when I was tipping hot water on.

To stop the boiler failing, I have now sawn the end off the pipe, allowing the trapped ice to fall out.  I have wedged a funnel between the drainpipe, wall and condensate pipe to direct the condensate into the drain.  And at least it should be easier to defrost now.

But it's a horrid bodge, and I can't leave it like that permanently.  Can anyone think of a permanent way to solve the problem, so it's less likely to ice up, or more easy to defrost if it does?

Carrot007

(afaik) There really should not be enough condensate to cause this problem.

Are you sure water from elsewhere is not getting in the pipe.

grumbler

Carrot007 said:

(afaik) There really should not be enough condensate to cause this problem.

you are mistaken

Norman_Castle

If the bodge works for the few weeks a year we have genuinely cold weather I'd live with it. I've often wondered why there isn't an internal tap to drain into a bucket for the duration of frozen pipework.

grumbler

Ectophile said:

The pipe had an L-shaped end on it, to direct the condensate into the drain.  The drainpipe is in the way, preventing a nice vertical run straight into the drain.  Unfortunately, that same L-shaped bit tended to trap any ice inside the pipe even when I was tipping hot water on.

Can you post a picture?

EssexExile

Is there any way you can route the condensate to a drain in the house? I had the same problem because of the idiots who installed my boiler, luckily my boiler is in the garage so I re-routed the condensate to the drain in the floor.

coffeehound

In the big freeze when this was happening on a large scale (2009??) they were recommending fitting trace heating along the length of the drain pipe, controlled by a frost stat.  Seems a bit OTT but if it gives peace of mind, perhaps it would be worth it.

fenwick458

grumbler said:

Carrot007 said:

(afaik) There really should not be enough condensate to cause this problem.

you are mistaken

yes they are. normal condensate output into freezing conditions is just asking for trouble. a simple solution I had whilst I lived at my old house where the condensate was exposed to the cold, was just to pull out the joint directly below the boiler whilst it was freezing, and put a 2l bucket there. I did this in the winter of 2010, and never again until 2017 when I moved out. it's only something you'll ever have problems with in an extreme cold snap, so if it's possible to sort cheaply as did then i'd go for that first. yeah I know you can get the condensate rerouted through the house (but if that was cheap and easy they would have done it in the first place, right) or even installing condensate traps or condensate heaters, but they all seem to me like an expensive solution for something that only happens once in a blue moon

John_the_Boy

A few options:-

1. Better insulation
2. Bigger diameter pipe
3. Better incline on the pipe
4. Heated pipe element
5. Route the pipe internally if you can

grumbler

Mickey666 said:

Lagging cannot keep a pipe warm, it can only slow down the rate at which it cools.  If the temperature remains below freezing for a while then the pipe will also reach below freezing.

True, but what I see at my friend's house (my boiler isn't condensing) is that the water is discharged periodically in pretty big amounts and it's not cold. With a 32mm plastic pipe without horizontal parts there should be no problems even if it's temperature is below zero.

bris

What size is the pipe? Some idiots run 21.5mm externally and don't even lag not that that would help much.

The external pipe should be at least 32mm but in the extreme conditions we have been getting this week that may not be enough so upping it to 40mm might be needed, if it even helps at all in these conditions as it freezes soon as it hits the outside.
As for not being enough condensate to cause a problem, a boiler will produce about 2 litres an hour so it doesn't take long to fill the boiler.

I always think this looks terrible though so always try to fins an internal route, which is possible  95% of the time but some installers are lazy and take the easiest path, which is a hole in the wall and down to the ground.