Vent pip in loft in the way

[waheed357]

Hi,

I have a, what I think is a plumbing vent pipe in the loft. Its going through a boxed in space within my ensuite behind the existing shower space. I want to open the space and extend the shower area but this pipe is in the way. It is quite big too. Is there any way I can reroute it or make it smaller so that it sits within the wall and not take as much space? Basically I want to integrate the boxed in space within the shower area but that pipe is in the way (right behind the electric shower in the photo). There is another vent (I think) on the other side of the house which doesnt go into the roof. Any help with this would be appriciated. Thanks

 

[CountryFan]

Yes it can be reduced in size to not less than 75mm for single or 2 storey properties. Or perhaps change the air admittance valve on the other one for the 110mm on existing and vice versa.

 

[waheed357]

75mm is still going to be too big. is it not just for the gases to escape and air to enter.......can it not be reduced to 40mm or 50mm? Sorry not sure what you mean by changing the AAV of other to 110mm as i think its already 110mm.

 

[waheed357]

is there a reason for it to be at least 75mm? If i reduce it, it would be just from floor boards to ceiling and then it would go back to 110mm from loft to roof. Is that something i can do at all or a no go?

 

[Madrab]

If the stack you want to move is dry and is just to vent then yes it can be moved, where to is the issue I would suggest.

Any dry section of a 110mm vented stack needs to be of sufficient size to vent the wet section of the 110mm soil pipe adequately, hence the min dimensions. You'll find it in Part H of the Building Regs.

 

[CountryFan]

Sorry not sure what you mean by changing the AAV of other to 110mm as i think its already 110mm.

Your last photo shows a white cowl, which is an air admittance valve - can this be swapped with your proposed stack?

 

[waheed357]

Your last photo shows a white cowl, which is an air admittance valve - can this be swapped with your proposed stack?

You mean change the stack with AAV to vent it through the roof? If thats what you mean, I dont think i would be able to do that. I know the regs say minimum 75mm but if only a section of the pipe is say 40mm or 50mm, would it make a huge differennce to airflow?

 

[denso13]

50mm would work but I think it is only right that we point out what the guidance says, which is minimum 75mm.

 

[Madrab]

The trouble starts when there's a lot draining at the same time, and what volumes are in play, that's where the min spec comes from to release both negative and positive pressures. The regs are usually best case and would 50mm work, probably. The regs are more for when the LABC comes along and signs things off but the size is calculated against volumes flowing in a 110mm pipe as per design standards. It also needs to be kept in mind that the vent isn't just for the stack, but also vents the drains and anything else connected to them and where you are in the main run re your neighbours etc, which is why at least one open vent like that is always best to be kept as open vent and not topped with an AAV.

What size you use is absolutely up to you and are there major, show stopping ramifications of not using 75mm, probably not but if there are issues in the future, then it may need re-visited.

 

[Koolpc]

75mm is there for a valid reason. I wouldn't go changing it.

 

[Madrab]

I guess the only trouble with it being 75mm is - there isn't any standard 75mm plastic for soil stacks, cast is the only stuff that comes in 75mm, which in essence is 3". Closest is either 68mm rainwater or 82mm soil pipe, which seems a bit stupid if the regs quote that size.

 

[CountryFan]

I guess the only trouble with it being 75mm is - there isn't any standard 75mm plastic for soil stacks, cast is the only stuff that comes in 75mm, which in essence is 3". Closest is either 68mm rainwater or 82mm soil pipe, which seems a bit stupid if the regs quote that size.

Au contraire https://www.plasticpipeshop.co.uk/75mm-2-12-Grey-PVC-Pipe-10-bar-PN10-25m-Length_p_5317.html, just ain’t cheap!

 

[Madrab]

Au contraire https://www.plasticpipeshop.co.uk/75mm-2-12-Grey-PVC-Pipe-10-bar-PN10-25m-Length_p_5317.html, just ain’t cheap!

Absolutely, and of course any size of PVC pipe can normally be had these days but that's specifically PVC pressure pipe, hence the price. That's more for commercial or industrial use and is specc'd up to 10 bar to can carry mains potable water etc. It is also chemically resistant so can be used in medical settings for pumped waste runs etc as ABS will tend to break down with some of the chemicals they use for sterilisation and cleaning, it's not really designed with soil stack work in mind. Hence the wording :-

there isn't any standard 75mm plastic for soil stacks.

 

[Hugh Jaleak]

Au contraire https://www.plasticpipeshop.co.uk/75mm-2-12-Grey-PVC-Pipe-10-bar-PN10-25m-Length_p_5317.html, just ain’t cheap!

Used a lot in the Water Industry for discharge pipework from Sewage Lift Stations, Water/Sludge movement on Treatment sites, lighter and easier to work with than steel pipework, depending on situation.

No purpose designed fittings available to my knowledge to join that to 110mm Soil/Drainage, you would probably need to look at a Fernco/Flexseal type connector to join the two types of pipework.