Condensate pipe.Definitive answer?

Inforapennyinforapound

I have trawled the various threads on the condensate pipe and seen various answers to this:

I want to prepare for winter and my boiler has an outside condensate pipe with a reasonable drop into the waste pipe.
Last winter caused no problems however i hear that this winter could be worse.

I have a plastic pipe which is 43mm diameter but not lagged.Will lagging help and if so is there any type of special insulation i should be looking for?

I welcome any opinions/experiences.

Thank you

Canucklehead

Hi,

If your boiler discharges condensate in bursts by siphonic action,
the outside pipe is 43mm through the wall before it reduces to 22mm you should survive as you did last winter.

I assume the length of run is not excessive, as you would have had a problem last winter.

If you are concerned, insulate with external grade insulation, Armaflex is one such brand.

It is glued along it's length after fitting, so no gaps.

It is expensive, but probably cheaper than trace heating.

More (different) definitive answers will probably follow.



GSR

garethgas

That would be my difinitive answer too.
Frankly, if you survived last winter I wouldn't worry too much once you've insulated it.

Inforapennyinforapound

Canuckle,the pipe coming out of the wall is quite narrow but it immediately drops into the 43mm pipe.Its quite strange in that there is no flush fitting i.e the small pipe just sits inside the larger pipe with a gap between the two.

The run to the waste is about 12 feet.

Thanks garethgas.There were so many people saying"Do this,dont do that etc etc" |Its allayed my fears somewhat. I dont know if its 'siphonic'..its a Baxi thats all i can say.

ariba10

If the gap where the smaller pipe enters the larger pipe is big enough, I would be inclined to pour some boiling water down it daily during a cold spell.

Canucklehead

Hi,

http://www.energysavingtrust.org.uk/Publications2/Housing-professionals/Heating-systems/Domestic-heating-by-gas-boiler-systems-2008-edition

Pages 42- 46.

You have 43mm waste, so well sized I would look to stop freezing draughts where the overflow meets the 43mm.

As said, you made it through last winter.

GSR

ormus

with a decent fall in the pipe, i doubt you will have any problems this winter.
all the frozen pipes last year were caused by bad installations. there is no basic design fault with condensing combis.

ListysDad

As C'head said, insulate with either armaflex or tufflex and a minimum of 25mm wall. DO NOT squash it and glue all joints so the vapour seal is kept intact. Both are nitrile based products and do not shrink when exposed to cold temps SO LONG as it is fitted so NO air gaps exist as described. This also means making sure the gap around the top of your 40mm pipe is closed. Lastly, with pipe that size its important that you keep the end clear as often drips freeze as they hang off the end of the pipe and that then builds back up. Tapping the pipe during really cold weather helps dislodge 'em.

The advice to fit larger bore pipework for condensate pipes is wrong. The reality is that it should all be run in the std 22mm but properly insulated by a MINIMUM of 25mm wall nitrile based product such as that above. By having larger bore pipes it simply allows air currents to circulate and that speeds up the freezing of the tiny droplets coming from your boiler.

Lastly, be under no illusion, insulation is NOT designed to stop freezing; it can't. All it does is slow the process. To stop it completely needs an equivalent amount of heat as is being lost putting back and that means trace heating.

Signed Saddo Dave!

Harryo

ListysDad wrote: »

The advice to fit larger bore pipework for condensate pipes is wrong.
Signed Saddo Dave!

Very risky saying that. Both the boiler manufacturer's installation instructions and http://www.energysavingtrust.org.uk/Publications2/Housing-professionals/Heating-systems/Domestic-heating-by-gas-boiler-systems-2008-edition (plus all other authoratative guides to my knowledge) state the pipe should be enlarged under certain circumstances.

brig001

Surely the definitive answer is to run it inside. I assume this can't be done.

Canucklehead

ListysDad wrote: »

The advice to fit larger bore pipework for condensate pipes is wrong

Incorrect...see here p. 41 onward.


GSR