New oil boiler - condensate query

26 Nov 2007
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United Kingdom
I live in the sticks in Scotland and am at the point where the 25 year old Camray oil boiler has had 3 major rebuilds to its firebox and had better be replaced before we get any further into this winter. This a regular/non-system boiler which is hung externally on a north wall.

My problem is condensate disposal. I cannot run it into the drains as I have a septic tank. I am aware of the lime ground soakaway but am concerned about freezing in the >500mm 'horizontal' run to the soakaway.

Two options seem to exist - a lime cartridge fitted inside the boiler housing such that the disposal can then be into the main drain pipe, or the other thing I've seen mentioned is a condensate syphon, again fitted in the boiler, which does away with the trickle problem of the condensate and thereby overcomes the potential freezing hazard.

Any guidance would be appreciated.
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Look at 'Trace Heating', to prevent the pipework freezing. If the condensate drain freezes, then the boiler will shut down, I would be concerned about the possibility of terminal boiler damage if that were to happen.
The pipework outside should be 32 mm and why not put the condensate into a soak away just outside and cover it over to stop the frost I live on isle of Lewis and have no probs with it.Bob
You can run it into the septic tank. The volume will not be great enough to affect the pH of the tank.
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Many thanks for the replies guys.

Trace heating I had thought about - can that go underground?

Oilboffin from Lewis - doesn't the presence of the sea and atlantic currents protect you from the occasional -20C ?

snb - as i live alone and don't have a reasonable family input to the septic tank, I'm a bit wary of that suggestion.

Two other options I've found - one is the cartridge containing a replaceable lime block that could go into the boiler enclosure, and then I could use the normal drain. The second is something called a condensate syphon which accumulates the condensate and then releases it by syphon action and avoids the 'dribble'. Any comments?
As long as the external pipe is large enough (32mm or even 40mm)then freezing shouldn't be an issue, you can always then lag that pipe too. You can also get an inline neutraliser that works as the condensate runs through it, place anywhere on the condensate run.

Some boilers already incorporate a condensate syphon trap that releases all the condensate in one go then fills up again.
Thanks Madrab - that's enough for me to work on, together with the fact that you're likely to get the same frost levels as I.

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