Condensate Pipe On Combi Boiler ?


The condensate pipe on my combi boiler comes out of the wall and rests in the hopper of a downpipe but with this rather cold weather that we have all been having, it has tended to freeze up quite a bit.
This got me to thinking.
The basin and bath waste pipes never seem to freeze up and these are directly into the soil pipe. I assume, rightly or wrongly that this is because (a) the ubends are inside the house and (b) because of the gasses inside the soil pipe come up into the waste pipes.
Working on theory (b), would it help if I take the condensate pipe from the hopper and feed it into the bath waste pipe using a 'T' connection and reducing plug thereby keeping the open end out of direct contact with the outside air. I have plenty of drop on the pipe to do this, or should I lag the pipe, though I don't think lagging is the answer.
Your thoughts as always would be most gratefully appreciated.
Kindest regards,
James
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the_constructor wrote:

much useful thermal energy in drain farts. Routing the condensate pipe (and trap)internally into another part of the waste system should work provided that there is no petty fogging regulation against doing it that way!! I quite agree that lagging is not the way to stop this.
Bob
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condensate pipe will flow through even ice. I have had that pipe sticking out of the wall now for more years than I can remember and never a drop. Ginge
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Ginge wrote:

Your not thinking of the emergency pressure release pipe by any chance are you?
A condensate pipe would either give a steady stream of water when the boiler is running, or "batches" of water delivered every so often if the boiler had a syphonic trap
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the_constructor wrote:

The basin pipes etc don't freeze because the water is dumped down them in batches rather than a trickle. If you were to leave a tap dripping in a basin you may find a different result.
Most condensing boilers include a concentrate trap that is also designed to empty periodically rather than in a continuous stream for the same reason. The open hopper will cool the passing water faster as well.
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John Rumm wrote:

When you say 'freeze up' do you mean it does actually block? As in, do you genuinely have a problem... if not, then if it ain't broke, don't fix it!

I agree with that... plus, if you do have a problem then the best way to resolve it would be to reroute your condensate pipe so it tees into a waste pipe *inside* the house. I suppose, arguably, if you do have 'trickling' condensate then as John suggests, this might transfer the problem to the sink(?) waste pipe instead, however due to its larger diameter it will certainly be less susceptible.
David
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Another factor is that the condensate pipe is usually 21.5mm (overflow type) pipe, but it's supposed to be 32mm minimum if routed outdoors. Do you have a run of 21.5mm plastic outdoors? Sometimes I see this, but it's been protected by 22mm pipe insulation.
Condensate from my boiler is luke warm, and that seems to prevent it from freezing. Many years ago, I installed a dehumidifier which ran permanently with a plumbed-in condensate drain pipe. For this, I ran a length of resistance wire (in PTFE insulation) along the inside of the condensate pipe and extending an inch or so from the end. I ran it from a low voltage AC supply on an outdoor frost stat. That worked fine. There are more professional equivalents of this available, but they are not at all cheap (tend to be used on things like outdoor sprinkler installation pipework).
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Andrew Gabriel
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boiler manufacturer, as the condensate pipe run kept on freezing, despite being the pumped variety. The pipe would block, the boiler flood, which would immediatly halt, but this repeated happening corroded the inside of the boiler. Went through 3 boilers in 7 tears, all under warranty, before switching to non condensing. Apparently a condensing boiler should never have been fitted in this location, a detached'ish garage, due to having have a long run of condensate drain pipe. One fix tried was heat tape on the pipe, but as he found out that was disipating 100W 24/7 and was not pleased when this was discovered.....
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We had that, fixed it with a small plastic bucket as a tundish (Farmers' shop calf-feeding bucket - they're thick plastic and pretty coldproof). If it did freeze, the bucket was several days reserve capacity.
Another fix is one of those foul drain air admittance valves, with the flappy plastic bag valves, on the outfall from the condensate drain. If you can stop air whistling up the pipe, you've solved most of the freezing problem.
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Yes. A HepVo trap near the end of the condensate pipe run that stops -0C air running up the pipe, and heavily insulate the condensate pipe and trap. Replacing a condensing boiler was far too drastic. Appears the boilers makers knowledge doesn't stretch to pragmatic installations.
Also 32mm pipe must be used where there is a possibility of freezing, or run outside.
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That's the beastie
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wrote:

If exposed to freezing air any moisture on the trap membrane could freeze and then another blockage. They are best in a position where they are unlikely to freeze and fitted vertically.
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wrote:

I think the boiler was fitted to a wall in the garage connected to the house via a short un heated corridor, fitted with worktop and storage units, with the gas and water pipes connecting via the tiled roof space. I suspect this is just a "standard plan" house originally design for non-condensing boilers.
The boiler condensate pipe left the garage and went along the outside of the unheated corridor to a foul water drain, probably a run of over 5m + numerous bends. It was apparently originally in 19mm plastic which froze the first winter in the house, flooding the boiler and corroding the internals. This freezing happened each winter only when wind was blowing in certain direction. Boiler was under British Gas maintainance who by the time they turned up the drain pipe had thawed, just drained the inside of the boiler.
In its 2nd year the boiler failed due to internal corrosion due to repeated flooding and the house builder replaced the boiler and changed overflow to 32mm pipe run. This again froze a couple of years later, this time builders didn't want to know, BG wouldn't service until freezing over flow fixed. Local plumber fitted 100W of heat tape to overflow pipes, BG again fixed the flooded boiler. Again bolier failed this time corroded ignition contacts due to previous flooding, BG wouldn't repair stating "it had been incorrectly fitted allowing it to flood" and wanted 2300 for new boiler (only 4 years old at this stage). After much fighting between BG and boiler manufacturer, boiler manufacturer supplied a non condensing version of the boiler, after having admitting fault that the boiler should never have flooded even if the drain pipe was blocked.
Non condensing boiler was fitted and my boss has had no issues for the last 5 years.
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wrote:

What usually happens is residual water at the bottom of the pipe freezes, he next batch of condensate runs over this ice and some stays. That freezes. Then there is a build up of ice in the pipe. If there is drip it will freeze up, as happens to dripping Pressure Relief Valve pipes. Then the boiler blows the expansion vessel.
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wrote:

The guy who fixed my combi had a look into installing a condensing boiler in it's place. The nearest drain was about 3.5 metres away and he reckoned that was too far for an external run with the risk of freezing up. He advised fitting another more up to date combi but as the old one is still going strong after 400 of repairs over 5 years I think we'll wait until it dies.
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