Heating cable question

The most common method to avoid freezing without heating the pipe is to keep the standard 20mm pipe as short as possible and feed it into a wider pipe such as 40mm diameter. We had that problem at the last house where the boiler was in the garage and initially had a 20mm pipe run of at least 2.5m . After we replaced the run with the 40mm we never had a problem again. I noticed the maintenance team did the same for a number of flats nearby.

Another trick for handling condensate, is to have a buffer (like a large barrel) to store up the fluid, then have a pump that pumps down the barrel when the barrel is full. Passing large slugs of fluid down a drain line, makes it easier to keep ice from building up in a pipe. Small slugs of fluid, don't keep the pipe warm enough. A barrel sitting in your house, that barrel of water has a decent thermal capacity.

You also want to do your rise over run analysis, and make sure no part of the external line is "flat". As a residue in a flat pipe can freeze and build up during the winter.

I agree with the observation about drain line diameter. Drains are deceiving, and the line should be made multiple times as big as logic would dictate. I've learned about this, just from having lines plug up (rather than a freeze up) on me, that a larger line was in order.

To clear a freeze up in an outside drain line, I use a plumbers snake (the kind with the coiled steel, not the flat metal strip type), and sister a quarter inch (fairly small diameter) poly tube with it. I take electrical tape and secure the plastic tube to the snake, with one turn of electrical tape (don't build a huge blob of tape). Place one piece of tape every six inches or so (you don't want the plastic tube to snag on something during the trip). You run the snake down the hole until it hits ice. Then connect the plastic tube to the hot water tap at the sink, and send some scalding hot water down the tube, to the ice interface. As the ice melts, you'll need to give the snake a little push every couple minutes, to keep the plastic tube "near the work". It took about ten minutes, to clear my one and only ice plug that way. When you do one of these, you don't know how many feet of plugged line there is.

When you do this, the drain line fills with tap water, and the water will run out of the open end of the drain line. I place a piece of plastic guttering (I keep a few pieces for fun) near the end of the pipe, and redirect the overflow some place that is not messy.

Paul

Many boilers in the UK already have this type of arrangement. The condensate gets stored in a (small) container in boiler and when reaching a threshold level the contents of the container is automatically syphoned out in one go. The process then repeats. The condensate is dumped occasionally in a large "slug" rather than being constantly dribbled down the pipe. This assumes that the condensate trap is working as it should be cleaned out with every annual service*.

When my mother had a British Gas boiler service contract most of what should have been done on an annual basis was never performed.

I have had a heating tape for the same issue for a number of years.

It came from

Although self-regulating, it has a thermostat. I feed it through a power meter, so that I can log its performance. Most years recently it hasn't even turned on, as we have not had prolonged hard frosts.

I guess that without the thermostat, the tape may well draw much more power, pointlessly.

Worth it for the reassurance - the year I bought it I had significant freezing issues.

Chris

Ours froze in that cold winter a year or two back.

We have a service contract and the chap turned up, dried it out etc, and got it going. He recommended just improving the insulation and the way the water drained, so it couldn’t collect.

I adjusted the pipe arrangement outside and added some of that foil type ‘bubble wrap’ insulation - in comes in rolls like wide tape.

So far, so good.

Youngest also had their’s freeze. Again, their were advised to look at the pipe arrangement outside.

As I understand it, the water is warm / hot enough as it leaves the boiler not to freeze. Provided you can get it ‘clear’ before it cools and freezes, no problem. A pipe run which allows the water to collect or is ‘slow’, is asking for trouble.

Building regs say minimum 30mm ID,

The condensate store is part of the the problem, the water might be hot as it goes in but cools whilst stored until it reaches the emptying threshold. I checked the temperature of mine in the garage and at best it could be described as tepid only kept warm by the fact it was within the boiler casing. I can understand how the small quantity of condensate stored once released down a narrow pipe will spread out and as a result easily freeze. Once we went to a 40mm pipe run we never had any further problems with freezing condensate.

When we moved into the bungalow I found the condensate pipe ran under the floor emerging through a wall and went a short distance underground to a manhole. I am surprised it never froze as it was not very deep underground. The condensate pipe now runs directly into the soil stack which is in the centre of the house, it runs mainly in 40mm waste pipe with a U - trap in part of the run to block sewer odours and the pipe also connects to the PRV through a Tundish . Whoever installed our boiler originally plumbed the PRV to simply empty under the floor.

Richard

Would plastic pipe be better than copper? I imagine that condensate in a cold external copper pipe would very quickly have any heat sucked out of it.

Update. Went to check out my daughter’s condensate drain. She’s now covered it in loads of insulation so I can’t even see what size the pipe is! ;-) It does have a short horizontal section so that might be something I can address. Until it freezes again I think I’ll just leave it.

Tim

I slide the plumber snake down, until it hits the freeze, then measure the amount of snake to determine roughly the frozen spot. Because part of unclogging it, is figuring out what to do about it for next time.

Paul