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boiler condensate drain

  • 05-12-2021 11:24pm
    Registered Users Posts: 188 ✭✭ declanobrennan

    Got the new Viessmann combi boiler for a house renovation installed in the attic. The plumber has run the condensate drain pipe out through the back fascia board where it discharges the condensate into the rain water gutter and downpipe. Two questions:

    1. is this kosher? Does it meet regs?
    2. does this contaminate any rainwater going into a water butt on the down pipe - I was planning to use this for gardening!

    The Viessmann manual recommends connecting to the waste water pipe but I'm not sure if this is an option.




  • Moderators, Society & Culture Moderators Posts: 31,961 Mod ✭✭✭✭ Gumbo

    It should discharge into the foul system or a small soak pit, but this can depend on individual manufacturers.

    the tech installation book for your boiler will detail where it should go.

  • Registered Users Posts: 2,150 ✭✭✭ Yellow_Fern

    Is that a copper pipe? Could that freeze in harsh weather?

  • Registered Users Posts: 2,499 ✭✭✭ Car99

    Boiler condensate is very acidic and hence corrosive. Very low pH so I'm not sure it would be good for all types of plants/soil. I know this because my condensate pipe came dislodge where it exited the boiler housing the condensate corroded completely through the housing sheet metal in a relatively very short period of time .

  • Registered Users Posts: 188 ✭✭ declanobrennan

    thanks for this. The manual states it has to go into the waste water system or else it has to be filtered through a device ( I can't remember what the device is called). Is this the same as the soil/sewage system?

    The builder has said that because it is an old house (mid terrace in Dublin 8, 1950s build ) there is only one single discharge - effectively that waste water all goes into the same system as the rain water gutter. Does this make sense?

  • Moderators, Society & Culture Moderators Posts: 31,961 Mod ✭✭✭✭ Gumbo

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  • Registered Users Posts: 32,589 ✭✭✭✭ BorneTobyWilde

    Question, should a circulating pump run independently of an oil fired boiler. I find it strange that there can be an ocean of boiling water heated an in the system, but once the oil fire is off the radiators go cold, while if you turn on the tap there is piping hot water.

    Circulating pump stops when the oil fire stops. SO nothing is circualting

  • Moderators, Society & Culture Moderators Posts: 31,961 Mod ✭✭✭✭ Gumbo

    Not sure on an oil boiler.

    I can’t remember the last time I came across one tbh so I wouldn’t be best placed to advise.

  • Registered Users Posts: 32,589 ✭✭✭✭ BorneTobyWilde

    It's an oil cooker, stanley, but I guess that's the same.

  • Registered Users Posts: 188 ✭✭ declanobrennan

    Thanks. May I ask what makes you say this? Are you a plumber? Just wondering on what basis you think he is right?

    Seperately, is the waste water system the same as the soil pipe/sewer system? Or are they different things altogether?

    thanks for all the helpful replies on this and my other home renovation threads lads!

  • Registered Users Posts: 188 ✭✭ declanobrennan

    just found this in the manual for the boiler (Vitodens 050-w if you care to know...)

    Condensate from gas combustion equipment up to 200 kW combustion output - Up to a rated heating output of 200 kW, the condensate from a gas condensing boiler can generally be introduced into the public waste water system without prior neutralisation.

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  • Moderators, Society & Culture Moderators Posts: 31,961 Mod ✭✭✭✭ Gumbo

    Plumbers dont do drainage ;)

    Builder do.

    it’s in the Building Regulations. Technical Guidance Document Part H.

  • Registered Users Posts: 188 ✭✭ declanobrennan

    Thanks but actually there is very little in that doc about what to do with condensate (apart from it should be drained) but the document does refer to "Heating and Domestic Hot Water Systems - Achieving compliance with Part L 2008" which had lots of helpful info, in particular this line:

    Connection to external drain point

    If the condensate drain cannot be connected to an internal drain then direct connection to an external gully or rainwater hopper can be considered. A rainwater hopper must be connected to a combined system ie sewer carries both rainwater and foul water. The open end of the pipe should be terminated in the gully or rainwater hopper below the grid level but above the water level.

    Which brings me back to my original question - how do I know if the sewer system is a combined system? I guess I'll ask Irish Water.