I’m looking for some advice on the positioning of a soil vent pipe (SVP). I’m converting my loft and adding a bathroom directly above the existing bathroom, so there is already an SVP in roughly the right location. I’m also adding a velux window on that elevation. As a result, the SVP ends up very close to the window.
 

From what I understand, that shouldn’t be an issue in principle, but it does mean the vent needs to be at least 900 mm above the window opening. I’ve attached a sketch showing the existing arrangement in blue and the proposed arrangement in red.
 

My concern is that this creates a fairly tall, exposed vertical section of pipe (around 2.5–3 m) near the pitched roof. I can lightly restrain it back to the chimney, but it still feels like an awkward solution.Does this approach work in practice and comply with regs, or is there a neater / more sensible way of dealing with this?

 

Any advice appreciated, thanks!

 

 

 

 

 

Edited January 23Jan 23 by amin

Cross over behind the chimney and run up the side of the dormer. 

Leave it close to the window, get signed off, then push a Durgo AAV into the top of the then shortened SVP, so it no longer vents. It just needs to be higher than the pan of the 2nd floor WC, by around 200mm

 

Do you have another SVP on the house elsewhere? 

 

The neighbouring properties with vents to atmosphere will be suffice for venting the network sewers, you’ll not have any negative effect from ‘capping’ the SVP with an air admittance valve. Make sure it’s an outdoor rated one though. 

2 hours ago, Nickfromwales said:

neighbouring properties with vents to atmosphere will be suffice for venting

Unless they have done the same.

22 minutes ago, saveasteading said:

Unless they have done the same.

I’d be happy to roll the dice, if it’s not the only 2 houses within a few hundred yards.   

Appreciate the ideas. Going behind the chimney up dormer sounds like the easiest way to comply - will there be an issue with the number of bends required by this?

 

I won't have any other soil vent pipes, the neighbours definitely do have vent pipes. The AAV is an interesting one and would certainly look a lot better. 

 

The other thing I was thinking about was moving the vent pipe internally and going straight up to the right of the first floor toilet.

If it helps, the SVP can be reduced to 3” after the last WC is picked up. It’s only carrying air at that stage so capacity is no longer a factor. 
 

You can still T in a sink / bath / shower etc to the reduced SVP, it’s just solids that aren’t ideal at the smaller diameter. 
 

You can actually have a single WC feed into 3” pipe, but nobody does it. 

9 hours ago, Nickfromwales said:

If it helps, the SVP can be reduced to 3” after the last WC is picked up. It’s only carrying air at that stage so capacity is no longer a factor. 
 

You can still T in a sink / bath / shower etc to the reduced SVP, it’s just solids that aren’t ideal at the smaller diameter. 
 

You can actually have a single WC feed into 3” pipe, but nobody does it. 

I never knew that. 

It does make sense though. A 4" SVP can adequately vent a pretty large building. 

 

I have a 2" SVP on my little place, so that I could hide it behind the cladding. It works perfectly. I can only do this because I didn't have to comply with building regs.

40 minutes ago, Crofter said:

I never knew that. 

It does make sense though. A 4" SVP can adequately vent a pretty large building. 

 

I have a 2" SVP on my little place, so that I could hide it behind the cladding. It works perfectly. I can only do this because I didn't have to comply with building regs.

Indeed. 
 

Last MBC project, where space was tight, I took the 110mm and converted it to 2x 50mm where it was guaranteed to be dry / just a vent only, and then took the 2x 50’s to the attic space and fitted 2x 50mm AAV’s up there (so they could be accessible).

 

Done this a load of times and it works a treat, including going to 4x 32mm and back to 110mm with an “elephant foot” fitting upside down in the attic / service space, so I could use a 110mm AAV. 
 

Also have used 225x25mm ducting to take a vent up within a service batten void (another MBC build) with only 35mm to plant with. 

If position of SVP near velux is an issue , is chimney also an issue?

5 hours ago, FarmerN said:

If position of SVP near velux is an issue , is chimney also an issue?

You wont have your head up the chimney smelling for #2's  It's about the stench from the stench pipe aka SVP wafting into a habitable room.