Hiya guys, Currently doing up our upstairs bathroom in a 2 story semi. We currently have a standard 110mm soil pipe boxed in in the corner of the room taking waste from toilet, sink and shower which drops down inside walls to pickup kitchen sink waste then carries off out under garden to drain. Soil pipe carries on up bathroom corner into loft and vents normally through roof tiles. Now bathroom is quite small and we'd really like to get rid of the soil pipe and the boxing in to make bathroom bit bigger and more visually appealing. Our plan was to blank off soil pipe at just above t-pipe where toilet waste joins and add-on a 82mm soil pipe that goes out through wall, goes up exterior wall and then have an external air admittance valve on top. I preferred the idea of just putting an internal aav on the soil pipe inside put apparently it would have to be 200mm above the toilet waste pipe so would still result in some boxing in, something my girlfriend isn't keen on. We have also been told that having an aav will cause methane to build up in the sewer system. We have two open drains outside that im pretty sure are joined to soil stack, also next door is higher up the hill than us and has an intact normal roof vented soil stack. I believe methane is lighter than air so would it naturally gather at the highest point in the sewer system? We live in a 30 year old private estate and I have no idea how many houses are linked to each sewer system/how many vented stacks are connected. Also been told that if we are at the end of a chain of soil pipes, ours needs to stay vented. Is this correct? Anyone able to shed any light? Should we be concerned about methane building up if we put a aav on our soilpipe? I also wanted to ask would it be possible to 'cut out' the 110mm section of soilpipe visible in bathroom and replace with a much smaller pipe, say 1.5" thick (as this could be recessed into wall and still allow us to tile flush) and connect this smaller pipe at each end to existing 110mm soilpipe ends in attic and at t-junction behind toilet?
You cant fit the AAV on the branch, it has to be higher than the higest flood level which is usually above the wash basin. Anything lower and you are risking a flooded house every time you clean your teeth. Yes your soil pipe does need to be vented which is what the AAV does it alows air in and keeps the smelly air from getting out. Use this link it may give you some better answers, particuarly about the open vents on a shared run http://www.polypipe.com/cms/toolbox/Air_Admittance_Valve_Installation.pdf
Thanks for the reply We currently have a floplast valve: http://www.floplast.co.uk/products/soil-and-waste-systems/air-admittance-valves It does say at top of page: Product is A1 approved in accordance with BS EN 12380 - it can be installed below the flood level of connected appliances. But does state in other notes that should be installed a minimum of 200mm above any connecting waste pipes to the stack. I understand that it lets fresh air into the system without letting smells escape - but that is my question. If it doesn't allow anything to escape, will this cause a buildup of methane? Many thanks
I personally can't see any problem* whatsoever in just taking that reduced-sized 82mm pipe through your ext wall and upski as you describe, and chust terminate it with a anti-pigeon grill - like any vent pipe. No AAV needed, surely? It would have to be terminated high enough, like a normal vent. 82mm is surely plenty big enough to allow air in to follow, er, 'dumps', and also to allow full open ventilation without the need for any valve? Ergo - no methane. * But that's not to say there ain't one...
A lot of AAV's, Floplast 110 is one that has the option of reducer down from 110mm down to 82mm pipe, so I don't see an issue with DA's suggestion, I use to do that way myself.
Thanks for replies guys I decided to give floplast a ring and asked them about methane buildup. They said that because I have two vented drains in garden and next door has a normal vented soil stack that there should be no problem at all with methane build up. I think now we're going to go with simple option and just have an internal aav fitted 200mm above the toilet waste pipe joint and box it in.
Just reading this and its almost the same as what we are doing in our en-suite but soil pipe is in the middle of the wall so really looking to get rid of either out through the wall or by using an AAV. Plan is to move the sink from its current position (see below) to the wall where the stack is to allow for a bigger shower tray and have a nice work surface all the way along with a new toilet with a hidden cistern. But the point of my post is to nail how high the AAV should be. Floplast say 200mm, others say above the sink overflow. If its above the sink overflow then I need to move the stake to the outside of the house, if 200mm it a much easier job of cut and fit and I will have easier access to the AAV as I intend to hide in a cupboard. EDIT: Floplast exact wording: 200mm minimum above the highest wet entry point to the soil vent pipe. When they say wet entry point to the soil vent pipe for my situation to me that means 200mm above where the toilets join the soil vent pipe, not where the overflow of the sink would be as that joins below where the toilets join.
I could be wrong but my take on it with these new type AAVs, is it could go where the red line is. Providing that is the vent pipe and not a waste pipe from upstairs.
Not if you extend it above the roof, but you could have a short one and use a AAV which would look a bit neater.
Hey phil, your setup is very similar to mine, except my soil pipe is in corner of room. We are fitting our internal aav 200mm above highest entry point on thursday, will let you guys know how we get on
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