Flexible Ducting for a 110mm Soil Pipe

Discussion in 'Plumbers' Talk' started by KPE, Oct 3, 2017.

  1. KPE

    KPE New Member

    Hello. There is flexible (nylon?) wire could ducting in my loft that is leaking. There are several tiny splits in it. Over a period of time, this has damaged the ceiling of the bathroom below. This ducting goes from a soil pipe, up through the loft and out through the roof. The soil pipe is 110mm and the flexible ducting has been slipped over the end and ties with a zip tie. I want to replace the 3 meters of flexible ducting. But I cannot find anything this diameter. The house was built in 2000. Are pipes a different size now? So the first question is, where can I buy 3 meters of 110mm flexible ducting?
    Second question is, assuming I can find some ducting, how do I waterproof the join? A zip tie does not work. Should I cover the end of the pipe with a mastic of some sort before slipping the ducting over? (American web sites offer a product called Ductseal - a white solution that can be painted onto the pipe before adding the ducting. I have not seen anything like that on UK sites.)
    Many thanks. P1010344.JPG
  2. Isitreally

    Isitreally Well-Known Member

    Why not continue in 110mm pipe as it should have been.

    Also work out why water was able to get into the ducting to cause it to leak and repair that problem.
  3. DannyDoLittle

    DannyDoLittle Member

    IMG_3316.JPG Can't you do away with the ducting altogether and fit an AAV.. air valve that will allow air in but no bad smells out ;-)
  4. KPE

    KPE New Member

    Many thanks for your replies - they are much appreciated. I have had some time to consider what you have both written, particularly as this is an area in which I have little knowledge. So I have read up a bit on AVVs and I can see that this might be a simple and cheap solution. However, the flexible ducting goes from the 'floor' of the loft and up to an outlet in the roof. So, if I was to disconnect the ducting, I would need to somehow block off the roof outlet - or even have it removed and a new tile or two inserted. Solid piping is not really an option as two or three bends would need to be inserted. As for locating the origin of the water, this blows in through the vent in the roof. So, I really think the only simple option at the moment is to replace the flexible ducting. This I can do myself - if only I can find 3 meters of flexible 110mm ducting.
    P1010367.jpg P1010376.JPG P1010377.JPG
  5. DannyDoLittle

    DannyDoLittle Member

    Search for 110mm flexible ducting.

    There's loads to choose from.
  6. DIYDave.

    DIYDave. Well-Known Member

    You can use the common 100mm flexi ducting and join to the 110 soil pipe with a length of 100mm duct, which will fit inside the soil pipe;



    Should be a fairly snug fit but secure 100 pipe inside 110 with a smear of silicon and flexi end with either cable ties or gaffer tape

    Rain could be entering via the roof exit as you suspect or if you are extracted warm, moist air from say a bathroom, some of that steam will condense in the pipe runs, the longer the runs, the less steam will actually escape out via the roof. The worst sections for this will be the 110 soil pipe, especially vertical runs as the air inside the pipe will be very cold in a roof space in winter

    Can improve by insulated the pipes with foil wrap or other flexible insulating material

    I have 2 showers at home vented out via the loft and roof, although pipe runs are much shorter than shown. Fitted a condensation trap to the vertical soil pipe which is connected to 21mm overflow pipe. Tee'd this into the overflow pipe from cold water tank so just 1 pipe exits from roof line

  7. KPE

    KPE New Member

    Danny and Dave, thank you both for taking the time and trouble to respond. I still can't find 110mm ducting on the net - plenty of other sizes. DIYDave, your suggestion sounds good, so I will be popping in to Screwfix in Ringwood for some ducting and a length of round pipe. Thanks again, gents.
  8. Scott stevens

    Scott stevens New Member

    I know this is an old thread but just wondering how KPE got on with this? I have the exact same issue and there is no room in my lift space to fit proper pipes connecting the soil vent pipe and roof escape pipe. Would the solution recommended by DIYDave (using common flexi ducting which has a 10mm smaller diameter than the actual pipes) remain water tight over time? Ideally looking for durable ducting which will remain watertight connecting 2 110m pipes and is at least 1.5m in length. Any suggestions most welcome?
  9. rogerk101

    rogerk101 Well-Known Member

    What's wrong with the suggestion of fitting an air admittance valve? Much cheaper, much easier, and much more effective.
  10. Scott stevens

    Scott stevens New Member

    I read somewhere else that the air admittance valves should only be used if there is other soil ventilation in the house to allow the drains to fully breathe, ie it shouldn't be the main solution for soil venting. Does this not cause water to escape in the loft as well? Another reason is the need to maintain the valve. The area of the loft with the problem is in the extension and its really difficult to access and flares up my asthma badly. Keen to avoid having to go back up and check it every 6-12 months of possible.
  11. rogerk101

    rogerk101 Well-Known Member

    I consider AAVs as being fit-and-forget, i.e. I have never serviced one or even felt the need to.
    The oldest one I have was fitted 29 years ago and I still hear the very faint tell-tale rumble as it does its job. I would only feel the need to service it if I didn't hear it working.
    When working correctly they would NOT allow any moisture in your loft. Moisture would be the same as smell, which is exactly what they're designed to prevent.
    In all the situations where I have used them, they are the only vent for the soil stack, and I have never had a problem with them. In fact, thanks to having one, I was able to detect a partial blockage in my sewer line earlier than if I had an open stack because the toilet was slightly slower in emptying than normal. It was slower because the flush wasn't able to push the air forward (because of the partial blockage) and it also couldn't push the air backwards (because of the AAV). The sewer would have to have been completely blocked before I noticed it had I had an open stack, and that would have made it much harder to clear.
  12. Scott stevens

    Scott stevens New Member

    I'm really pleased to hear that about the AAVs, as it does sound like the simplest solution.
    The only thing I'd need to keep an eye on us any water entering from the roof vent. I fitted a mushroom cowl which should limit the water coming in and I can place a large container directly underneath to catch any water. I might have to empty it every year or 2 though.

    In terms of the various AVVs on sale would you recommend any one as being the best for this purpose?

    It will need to fit the wider end of a soil pipe by the looks of it which already has what looks like a ring at the top with a black seal inside. I think this is glued on or will be difficult to remove.

    Are all AVVs flexible enough to be fitted to different 110mm pipe ends?
  13. rogerk101

    rogerk101 Well-Known Member

    With a mushroom cover on top of the previous soil pipe, and the soil stack disconnected, why would you ever get any water coming in?
    I've used several different brands of AAVs over the years, and they all work well. Some are specifically indoor only, i.e. they mustn't be allowed to freeze, but others can cope with freezing.
    The ones I have used have just pushed into a regular coupling - either brown underground ones, or the black/grey/white ones. They must be mounted vertically to function correctly.

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