BISF Bathroom Refurbishment Questions

BISF Bathroom Refurbishment Questions 1

Hi all,
my next project will be refurbishing the bathroom as it is in a sad state. The previous owner of the house was in his 90s and presumably could not get into or out of the bath, so it was removed and a shower fitted instead (without making good the gap where the bath was). Water has got behind the shower tiles and damaged the plasterboard and generally the whole thing is in disrepair.
Anyway, I have a few questions. My initial plan was to do what the neighbours have done and remove the vent pipe and replace it with an air inlet valve. This has allowed them to put in a small built-in cabinet across the window wall and containing the basin and toilet which seems like a good use of the limited space. Also it means the hand basin can be moved slightly towards the end wall so it isn’t jammed up against the bath.
I was also thinking that removing the vent would ultimately make reroofing simpler and allow more space for solar panels (longer term plan).
However, speaking to someone else it seems that this breaks building regulations as you are meant to have at least one open vent in the system, and that the air inlet valve must be above the level of the basin outlet (theirs is just above floor level).
Just wondering what other people’s experience/knowledge of this is.
Also does anyone know what the vent pipe is made of? When I saw the neighbours’ removed it looked like asbestos but I didn’t look closely. They said it as cast iron, but I don’t think they removed it themselves, so maybe that as just what they were told.
My last idea, if it isn’t advisable to remove the vent pipe would be to remove the boxed-in covering and replace it with an exposed chrome plated or stainless steel one to save space and make a feature of it, coming up through a built in cabinet.


  1. Quick update on some more bathroom renovations.

    We’re having a new boiler fitted in the loft soon (hopefully!) so as part of the bathroom renovation I’ve been redoing the plumbing. I have put in a condensate pipe for the boiler in the wall between the landing and bathroom which then goes under the bath and ends in the bath waste pipe. Often these are installed outside on the front of the house for convenience, but this looks unsightly and external condensate pipes can freeze in cold weather which stops the boiler just when you need it most! So I thought I’d do this bit myself.

    I have also plumbed in a new shower on the same wall and taken the opportunity to take the hot water pipe up to the loft so that when the new boiler is installed up there this will be the main feed to the bathroom and kitchen, to reduce the pipe length so the taps don’t take so long to run hot.

    Also took the lighting cables out of their surface mounted conduit and threaded them through holes drilled in the studwork.


  2. I’ve also tried a new arrangement of the insulation to minimise cold-bridging. Before I left the original timber uprights with their special clips that attached to the steel stanchions and screwed the new studwork to those, but that meant there was only timber and not insulation covering the stanchions. This time I’ve removed all the original studwork and bolted the ceiling plate to the L-section steel above with high tensile bolts, with 50 mm blocks of wood to act as spacers and will fill that gap with insulation. This will mean that the insulation layers are staggered and the stanchions are behind the second layer of insulation.

  3. Here’s a photo of the boxed-in vent pipe in the bathroom. What my neighbours have done is to remove this but leave the soil pipe as it is boxed-in in the kitchen, and replace the vent pipe with an air inlet valve. They have a cabinet unit containing the toilet cistern, air inlet valve and handbasin that fits across the whole window wall up to the bath and I think it looks very nice.

    1. Ahhh Thanks Ed, I understand now lol. I have spoken to Paul Leer of Regent Maintenance for you. Paul has extensive knowledge of the roof area of the BISF house. He informs me that the vent pipe is in fact made from low grade asbestos. It couples with the top of the cast iron waste pipe at around original cistern height.
      The asbestos here is relatively low risk but obviously if being removed care should be taken not to damage it.
      If you need any further detail, you can speak directly to Paul. His contact details are available on his main website and he’s a great chap.

  4. Hi Marc, thanks for your posts. I wasn’t thinking of removing the soil pipe and putting it on the outside as that’s too much of a job and I’m allergic to external pipework!

    Scratching the little bit of the pipe that is exposed in the loft makes me think it is asbestos as I can’t think of any other material from that era that a pipe could be made of that can be scratched.

    1. Hi Ed, can you take a photograph of the vent pipe? I know you said it’s in a really difficult area to reach but it would be good to see.

      The stench removal and replacement only takes around a day but it’s all the other re-decorating where the boxes were and re-connecting that takes the time but it’s well worth it. To be honest though I’m struggling to picture what your neighbours have actually done. I normally associate the vent pipe with what goes up through the loft and out the roof. Did they just remove half of the stench pipe and put in a valve or something?

  5. Hello Ed, I’ve carried out a couple of stench pipe removals which does indeed involve removing the existing cast iron pipe from both the kitchen and bathroom. This frees up much needed space and is pretty easy to undertake.

    The flue is like a smaller version of the fireplace flue and again comes in two pieces if I recall correctly but may have been three. It was simply a case of removing all the boxing in from around the pipe at ground and bathroom floor levels. Then removing the pipe by either cutting or smashing. I used smashing which was easy once the first pipe breach was achieved.
    The pipe sits in a clay collar at floor level and simply lifts out. Some have some plumbers mate type sealant which helps mating the the join.

    Once the cowling and pipes had been removed and of course dismantling the associated waste pipes from sinks and toilet etc it was simply a case of buying a new plastic stench pipe and bend. The pipe was affixed to the outside wall of the house like a traditional pipe is and the bend went back into the house through a new hole before being fitted back into the collar.
    All in all it wasn’t difficult but of course different waste pipes and fittings were needed.
    I will see if I can obtain a photo of the outside of the house.

  6. OK, it seems I’ve answered one of my questions already. I got down on my stomach in the loft and scratched the vent pipe with a nail and unfortunately it is asbestos so I guess if I’m going to remove it I’ll have to try and take it out in one piece.

    My dad who is a builder (!) seems to recommend ignoring the building regulations and removing the vent and replacing it with an air inlet valve.

    1. I’m not 100% sure of what your vent pipe looks like though Ed. The roofs that I have worked on have all been replacement steel roofs that had a plastic vent pipe leading up to a vent grid on the roof itself which made it easy. If you did decide to mount the stench pipe on the outside you wouldn’t need the vent plus the cost of the pipe itself was much cheaper than expected, it was just all the grunt work that took the time and re-drilling new holes in the steel upper skin to allow the bath/ sink / toilet waste a direct exit.