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Housing - New Build: Inside or outside for a soil-pipe?

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    • CommentAuthortony
    • CommentTimeJan 14th 2012
     
    In heat loss terms alone is it best to have internal or external soil and vent pipes?
    • CommentAuthorGavin_A
    • CommentTimeJan 14th 2012
     
    I'd think it'd depend on whether it's an open vent or has a AAV fitted.
    • CommentAuthortony
    • CommentTimeJan 14th 2012
     
    Ah, so two different answers then?
    • CommentAuthorFred56
    • CommentTimeJan 14th 2012
     
    Interesting. I had not thought of that. I put them inside because they look so ugly on the outside. But, heat loss could be significant. I always insulate round them to keep the noise down but even still there must be a chimney effect of some type. Too late for this project but I was questioning anyway as the path through to the roof has penetrations that have to be sealed to preserve airtightness.

    There is a heat loss path through the wall too. I have lived in a few houses where the basin traps have frozen when it got really cold.
    • CommentAuthorMike George
    • CommentTimeJan 14th 2012 edited
     
    If its an open vent, then an outside vent is best as the heat lost is via the water only, which will be lost anyway. If its inside [and then up and out through the roof], then the air in the stack will have been heated to some degree and result in stack effect and greater losses.
  6.  
    Posted By: Fred56I always insulate round them to keep the noise down but even still there must be a chimney effect of some type


    But they can't be open to your living space surely - aren't all connections to soil pipes via P-traps? If there's a direct air path, you'll fill your house with sewer gas.

    When we opened up the walls during our renovation, I insulated around the stack as one of the pipes is also connected to a roof drain. Ice cold water coming down in winter could cause condensation so I wanted to avoid this. Over here, of course, no-one has outside pipes :)

    Paul in Montreal.
    • CommentAuthorGavin_A
    • CommentTimeJan 14th 2012
     
    Posted By: tonyAh, so two different answers then?

    I'd think if it's capped then inside would be fine, but if it's open then keep it outside otherwise you've got a 100mm diameter pipe of cold air dropping straight through the insulated envelope to undo some of the good work you'll have done insulating the rest of the house etc.
    • CommentAuthorborpin
    • CommentTimeJan 14th 2012
     
    Whether they create a heat loss or not, I would not have an external one. Ugly and the material degrades. House opposite us had theirs blown down in the recent wind.

    You may not have a choice as to whether you can have an Automatic Air Valve or need an open vent (depends if you are at then end of a long run). Always go for an AAV in the loft if you can IMHO.
    • CommentAuthorFred56
    • CommentTimeJan 14th 2012
     
    <blockquote><cite>Posted By: Paul in Montreal</cite>But they can't be open to your living space surely - aren't all connections to soil pipes via P-traps? If there's a direct air path, you'll fill your house with sewer gas.
    </blockquote>

    The SVP goes through the living and roof space sealed from the envelope and vents through a purpose made tile. The location of the vent tile is governed under building regs in terms of proximity to other opening.
  10.  
    I went through these thoughts some time ago and reached a conclusion that we're happy with.

    The soil pipes are mostly inside the house and exit into the drainage pipes below ground. This is principally to avoid the ugly mess of connecting pipes on the outside. (On one side it won't be very visible and only one bathroom is served. We've made the decision to get the soil pipes outside as quickly as possible to avoid the need for a soil pipe duct down to the ground floor.)

    However, the soil vent pipe, i.e. the one that must be at the end of the drainage run and is primarily intended to help ventilate the sewer and provide a bypass in the event of suction, is external. This is just a clean single pipe from the ground up to above the roof line. No connections to anything in the house. Air will regularly be flowing through this pipe and it was too much of a thermal compromise to keep it inside the thermal envelope.

    I swing between wanting to get the soil pipes outside quickly to save the internal space and avoid flushing noise issues and wanting to keep them inside to avoid the outside being ugly. As far as I can see it's a matter of cosmetics more than anything else. The soil vent pipe is another matter entirely and needs to be outside.

    We did consider abandoning the SVP and going with AAV on the fittings. However, there was concern that this might not work so well in a house that is close to airtight, so we abandoned the idea.
  11.  
    Posted By: MarkBennettavoid flushing noise issues


    Noise issues can largely be solved using cast iron pipe - though probably no-one does that anymore. Except where I live and all plastic plumbing is not allowed, except for buried sewer pipes (and that was only finally authorized last year). Only copper and iron is allowed, even for drains.

    Posted By: MarkBennettAir will regularly be flowing through this pipe and it was too much of a thermal compromise to keep it inside the thermal envelope.


    If it's in a rectangular chase, it's easy enough to fill will blown cellulose though (which is what I did).

    Paul in Montreal.
    • CommentAuthorborpin
    • CommentTimeJan 14th 2012
     
    In my last build I used 32mm AAVs on Tees off the main run; never noticed any noise. At the end of the run (effectively the end of my house 35M from main connection) I had a 110mm AAV. I think the amount of air that is taken in is minimal in the overall scheme of things and even though I will have a virtually air tight house next time, I will have no issues with using AAVs.
    • CommentAuthorCWatters
    • CommentTimeJan 15th 2012
     
    In England I believe you must have at least one open stack, usually the one furthest from the public sewer. I believe AAV are only allowed on stacks between the open stack and the sewer.
  14.  
    My experience is that AAVs work properly for about 5 years, after this I have found that the rubber gets progressively harder allowing more and more smells to leak past.

    A question - does tor vent pipe have to be 110mm or can a smaller dia. be used?
    • CommentAuthortony
    • CommentTimeJan 15th 2012
     
    for single spurs here 50mm which is the minimum can be used

    I have seen 75mm used on old properties at the head of a run but 100mm now on new

    never seen less than 50mm
  16.  
    Posted By: CWattersIn England I believe you must have at least one open stack, usually the one furthest from the public sewer. I believe AAV are only allowed on stacks between the open stack and the sewer.


    No, it is possible to do away with the soil vent pipe altogether if there are more than a certain number of AAV, I think it needs 2 or 3 but can't remember the details.
    • CommentAuthorpmusgrove
    • CommentTimeJan 15th 2012
     
    Sorry Mark but I don't think you are correct. Building Regs are not very specific about whether only AAVs can be used but do refer to the need to reduce positive pressure in the system which any number of AAVs will not be able to do. Custom and practice is that the stack furthest from the main sewer should ventilate to atmosphere externally. I tried recently to convince a BCO that a house on its own package plant should have the positive pressure relief at the plant end of the system. He would have none of it and insisted on an open stack. I can see his point; a build up of gas to the top of the system could have some nasty repercussions!
    • CommentAuthorqeipl
    • CommentTimeJan 15th 2012
     
    In my house both WCs drain to a soil pipe under the foundation slab.
    All waste pipes drain to bosses in soil pipe branches that terminate below the upper 100mm of EPS floor insulation.
    The soil vent pipe rises from the underground soil pipe outside the building.
    The intention was to minimise heat losses via the pipe walls so that the only significant loss is the water going down the pipes.
  19.  
    Posted By: pmusgroveSorry Mark but I don't think you are correct. Building Regs are not very specific about whether only AAVs can be used but do refer to the need to reduce positive pressure in the system which any number of AAVs will not be able to do. Custom and practice is that the stack furthest from the main sewer should ventilate to atmosphere externally. I tried recently to convince a BCO that a house on its own package plant should have the positive pressure relief at the plant end of the system. He would have none of it and insisted on an open stack. I can see his point; a build up of gas to the top of the system could have some nasty repercussions!


    For example: http://www.hunterplastics.co.uk/download/29/Design%20Criteria.pdf

    Section 3.08, paragraph 7.3:
    "(a) For up to and including four dwellings, 1, 2, or 3 storeys in height, additional drain venting is not required."

    This just happens to be the first document I found on a quick search. I've seen the same kind of statement elsewhere.
    • CommentAuthorjamesingram
    • CommentTimeJan 15th 2012 edited
     
    So , if internal with a AAv it will take heated air in when required but wont it also give a bit of heat back from say bath water etc. heating up the soil pipe as it travel through the house to the sewer.
    as to flushing noise, hay we all do it , so what if we hear the odd plopping noise , isn't the just a classic british dilema
  21.  
    I have the soil stack down the inside of the rear wall as the building is built into the hillside at the rear almost up to eaves level. Then above the toilet connection it reduces to 2 inch pipe that follows the roof slope (the room is open to the ridge) by being cut into the lower part of the PUR roof insulation (the bit between the rafters not the bit over the rafters) then it vents to a ridge tile vent.

    Retrofit/refurb 450mm solid stone wall lined with 120mm Hemcrete (just enough to cover the pipe).
    Private sewage system (septic tank).

    I hate all external pipes as I think they are ugly.
    Plus they would have been on the front of the building - even worse.
    • CommentAuthorpmusgrove
    • CommentTimeJan 16th 2012
     
    Thanks for the reference from the BBA Cert for Hunters AAV. I will use this as evidence next time I have a discussion with BCOs on this matter. However from an engineering angle (rather than a regulatory one) we still need to provide somewhere in a system for positive pressure release. AAVs will not allow this (hence the requirement to have an open stack for more than four houses). I can only think that the BBA presume that the gases for one to three houses attached to a stand alone plant will escape through air leaks in the system. Probably correct but I would rather know where the gas can escape from and allow that escacpe high up than through a blown connection or a loose fitting drain cover.
    •  
      CommentAuthorjoe90
    • CommentTimeJan 16th 2012
     
    Posted By: qeiplIn my house both WCs drain to a soil pipe under the foundation slab.
    All waste pipes drain to bosses in soil pipe branches that terminate below the upper 100mm of EPS floor insulation.
    The soil vent pipe rises from the underground soil pipe outside the building.
    The intention was to minimise heat losses via the pipe walls so that the only significant loss is the water going down the pipes.


    is this not the best way to go? no heat loss from internal vent pipes going through the roof but a vent pipe from the outside underground drains to release gas/pressure?
  24.  
    Posted By: joe90
    Posted By: qeiplIn my house both WCs drain to a soil pipe under the foundation slab.
    All waste pipes drain to bosses in soil pipe branches that terminate below the upper 100mm of EPS floor insulation.
    The soil vent pipe rises from the underground soil pipe outside the building.
    The intention was to minimise heat losses via the pipe walls so that the only significant loss is the water going down the pipes.


    is this not the best way to go? no heat loss from internal vent pipes going through the roof but a vent pipe from the outside underground drains to release gas/pressure?


    In general I think so. It's essential what we are planning with one exception.
  25.  
    Posted By: qeiplIn my house both WCs drain to a soil pipe under the foundation slab.
    All waste pipes drain to bosses in soil pipe branches that terminate below the upper 100mm of EPS floor insulation.
    The soil vent pipe rises from the underground soil pipe outside the building.
    The intention was to minimise heat losses via the pipe walls so that the only significant loss is the water going down the pipes.
    If you go down this route then do you need Air Acceptance Valves at the top of the two internal stacks? Or do you only need these if there's more than one connection to a given stack?

    David
    • CommentAuthorpmagowan
    • CommentTimeJan 19th 2012
     
    I had planed to take my soil pipes out through the EWI (retrofit), fix them to the outside, then box them in with more EWI and render over this. The only area where the heat could get lost is out the top and as some have said there is a partial solution to this.
    • CommentAuthortony
    • CommentTimeJan 19th 2012
     
    The only reason to box them in outside would be if you felt that they looked ugly, otherwise a waste of time and materials and causes future accessibility problems (another reason why I dont like them inside)
    •  
      CommentAuthorjoe90
    • CommentTimeJan 19th 2012
     
    Posted By: davidfreeborough
    Posted By: qeiplIn my house both WCs drain to a soil pipe under the foundation slab.
    All waste pipes drain to bosses in soil pipe branches that terminate below the upper 100mm of EPS floor insulation.
    The soil vent pipe rises from the underground soil pipe outside the building.
    The intention was to minimise heat losses via the pipe walls so that the only significant loss is the water going down the pipes.
    If you go down this route then do you need Air Acceptance Valves at the top of the two internal stacks? Or do you only need these if there's more than one connection to a given stack?

    David


    In this situation I would put AAV's on the two internal stacks as I would not want to risk the flushing of the toilets pulling water out of the basin etc traps, I have not had 100% success with anti vac traps which should avoid this issue.
    • CommentAuthorqeipl
    • CommentTimeJan 19th 2012
     
    Posted By: davidfreeborough
    Posted By: qeiplIn my house both WCs drain to a soil pipe under the foundation slab.
    All waste pipes drain to bosses in soil pipe branches that terminate below the upper 100mm of EPS floor insulation.
    The soil vent pipe rises from the underground soil pipe outside the building.
    The intention was to minimise heat losses via the pipe walls so that the only significant loss is the water going down the pipes.
    If you go down this route then do you need Air Acceptance Valves at the top of the two internal stacks? Or do you only need these if there's more than one connection to a given stack?

    David


    Each WC and each waste boss has its own branch (very short underground stack) to the main soil pipe. The vent is the top end of the main soil pipe.
    The BCO (who seemed to be knowledgeable about drains - we spent some time discussing them) was happy with this arrangement.

    I can imagine a stack covering two storeys with WCs on both levels would need a vent at the top of the stack.
  30.  
    Posted By: joe90In this situation I would put AAV's on the two internal stacks as I would not want to risk the flushing of the toilets pulling water out of the basin etc traps, I have not had 100% success with anti vac traps which should avoid this issue.
    Could the AAVs be fitted under one of the sinks to allow easier access? What's an anti vac trap?

    David

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