freezing forecast.

[critcher]

what about this then, my condensate outlet pipe runs down outside wall from upstairs room, in freezing conditions these pipes are prone to freezing and blocking. What is the possibility of fitting a valve in the plastic pipework inside the house to divert the condensate to an internal tank when conditions outside are enough to freeze the pipe. The tank would have to be emptied manually, but is it feasable, and if so are there any regulations stopping me from doing it myself. If not possible, what is the best way to insulate these pipes?

[Bob Minchin]

Insulation will always be defeated by cold weather as the volume of water and hence energy content is very small. Re-route the pipework into a drain run inside the house. use 22mm overflow solvent weld pipe. you can get a variety of adaptors to whatever size drain pipe you have to hand.

[Dave Liquorice]

Donno but there is a (small) risk that flue gases could escape into the room. There should be a water trap in the boiler or an automatic syphon that stops gases escaping down the condensate drain.

The condensate drain shouldn't freeze. Find the installation instructions for your boiler (online?) and see what they say about the drain when outside. The pipe size normally steps up when going outside. It's very common for this not to happen though (installers have to carry two sizes of pipe, adapters etc) and frozen condensate drains is the result.

The automatic syphon feature is good as it dumps a relatively large volume of warm water in one go, rather than a continious cool dribble.

[critcher]

I was hoping to be able to direct the condensate flow inside in bad weather and outside during summer. My boiler is not in a very good position to do as you say, but thanks for the info. How much condensate is generated in these boilers? ie. 1 pint per day, per week?

[Nightjar]

On a friend's boiler, I simply used preformed insulation for 22mm copper pipe, covered with aluminium tape. It has prevented the condensate pipe from freezing for many years now.

[GB]

Just re-route the condensate pipe to an internal drain. Google condensate pumps, if this involves making the water go uphill. The pumps have a thin, flexible plastic hose that is very easy to run.

[Mark Carver]

Presumably the condensate pipe is (usually) a vertical drop from the moment it emerges outside, so where is the build of of water going to occur to create a frozen blockage ? Surely the moment the water falls over the 90 deg bend, it just drops at 9.81 m/s/s out and away, no time to freeze ?

This is what I imagine the arrangement is (randomly googled picture):-

[GB]

You should really explain this to icicles, which, if your theory is correct, really have no right to form. :)

[charles]

my what can happen, and I know of two instances is that insects can build a nest in the pipe, the first drop of water stalls and freezes and the next drop, etc.

[Mr Pounder]

I used the same insulation and just secured it with plastic tie wires. No problems.

[Mark Carver]

Ha, I ask because 24 hours from now, I'm going to be the proud owner of a condensing boiler, with external condensate pipe !

How about something like this ?:-

[critcher]

that diagram is fairly accurate except that the fall on mine is about 4 metres and at the bottom is a soakaway as there wasn't a drain available. The condensate pipe terminates in a larger plastic pipe about 35mm dia for about 30 inches, this then leads to the soakaway.

[critcher]

that doesn,t happen Phil, there is a auto syphon which activates at a predetermined level inside the condensate tank in the boiler and dumps a "slug of water" down the pipe

[Andrew Gabriel]

Mine generates a constant trickle when the burner is firing, but I run it at 45C/38C flow/return, which is about as efficient as it is it possible to be, so it generates maximum condensate. Unless you have large radiators for low temperature use, this is unlikely to pass enough heat into the house from the radiators, but it's worth trying if you haven't done so because if it works for you, it will save you gas.

One possibility is that yours is ejecting most of the condensate as fog from the flue terminal, which is also fine.

If yours is running at over 55C return, you will get little if any condensate as it's not running in condensing mode. In this case, it will be ejecting steam from the flue which condenses into fog when it mixes with the cold air outside. The difference here is that the fog appears an inch or so after the end of the flue terminal where it mixes with the cold air, as opposed to the case above where the fog can be seen coming out of the flue terminal because the condensing already happened in the boiler.

[Nightjar]

Not in this case. It is at an angle of about 45 degrees, to run into an existing drain gulley.

[Andrew Gabriel]

Here's one you can buy specially for that purpose:

[Andrew Gabriel]

I don't believe most condensing boilers do this, although a few do. The other thing that will trigger this behaviour is the use of a condensate pump.

Most have a syphon to prevent flue gasses passing into the condensate pipework, but that syphon has to remain full for safety.

[critcher]

Thanks for all the replies, I quite like the idea of the electric heater cable and have ordered a set.

[Andrew Gabriel]

I recall a posting, perhaps 15 years ago, from someone who had a condensing boiler fitted when they first became available in domestic power outputs. Plumber left the condensate pipe dripping onto the conservatory roof, which was fine until the first winter when an icicle several feet long came crashing through the conservatory roof.

I made my own for a dehumidifier drain pipe many years ago. I found the commercial products much more expensive than I thought they should be (although that one above is probably one of the cheapest I've seen). I made up a length of insulated resistance wire inside the pipe, with a small loop poking out the end before it returned back up the pipe. It ran off 18V AC, using a froststat positioned outside. IIRC, I ran it at 6W/m (and it was a 3m pipe).

My boiler generates a continuous stream of luke-warm condensate when the burner is firing, and it's never frozen in the 1m of 32mm plastic waste pipe it runs along outside. (Most boiler installation instructions require

32mm or larger diameter condensate pipework outside.)

[newshound]

Same sort of idea, but DIY and cheaper:

Assuming your pipe from the boiler to the external drain is vertical, you could just put a Tee above the bottom elbow and take that to your container. If the external drain freezes the water will back up and escape via the Tee. Probably worth making the initial run slope backwards towards the vertical pipe for a bit.