weird soil (vent) pipe configuration in loft

[sugerbear]

Hopefully a quick question about the house I am in as it looks like the soil pipe vent in the loft has been, for want of a better term, bodged.

The soil pipe runs at a 45 degree to the loft space (following the roof line) which is fine,
it then goes into the loft and has a 90 degree joint which make it point down at 45 degrees,
then a right hand joint to make it run along horizontally across the roof space
it eventually gets to the another 45 degree joint that make it point up and out through a flexible hose / roof vent.

/\___/ <<< is what is looks like in my best ascii art

the issue is that whoever installed it has managed to create a trap for any moisture and turn the soil (vent) pipe into a U-Bend. It now has a lot of water within it which I dont think is how it should work.

I think I need to change the pipe work so that the pipe is always level (or has a very slight angle) so that any moisture that goes UP the pipe can work its way back DOWN the pipe and go into the waste.

Have I got that right or has it been built this way for a reason?

[TA14]

sugerbear said:

it looks like the soil pipe vent in the loft has been, for want of a better term, bodged.

I think I need to change the pipe work so that the pipe is always level (or has a very slight angle) so that any moisture that goes UP the pipe can work its way back DOWN the pipe and go into the waste.

Have I got that right or has it been built this way for a reason?

Without studying your house in detail it looks like:
yes
yes
yes and yes

Why can't it go out through the roof where the first bend is? Windows?

[sugerbear]

TA14 said:

sugerbear said:

it looks like the soil pipe vent in the loft has been, for want of a better term, bodged.

I think I need to change the pipe work so that the pipe is always level (or has a very slight angle) so that any moisture that goes UP the pipe can work its way back DOWN the pipe and go into the waste.

Have I got that right or has it been built this way for a reason?

Without studying your house in detail it looks like:
yes
yes
yes and yes

Why can't it go out through the roof where the first bend is? Windows?

Three story building (with bedroom in the loft space) and I think it's a building regulation that says the vent needs to be x distance away from an open window so it can't just vent from the nearest point because that would be directly next to a window.

[sugerbear]

I think I may have found an alternative solution of using an air admittance valve and just doing away with all of the pipe work going into the loftspace.

https://store.jdpipes.co.uk/110mm-air-admittance-v...

[blueg33]

I had a similar stupid set up that actually leaked water and caused a damp spot on the ceiling. I removed it and installed an air admittance valve.

[Triumph Man]

sugerbear said:

TA14 said:

sugerbear said:

it looks like the soil pipe vent in the loft has been, for want of a better term, bodged.

I think I need to change the pipe work so that the pipe is always level (or has a very slight angle) so that any moisture that goes UP the pipe can work its way back DOWN the pipe and go into the waste.

Have I got that right or has it been built this way for a reason?

Without studying your house in detail it looks like:
yes
yes
yes and yes

Why can't it go out through the roof where the first bend is? Windows?

Three story building (with bedroom in the loft space) and I think it's a building regulation that says the vent needs to be x distance away from an open window so it can't just vent from the nearest point because that would be directly next to a window.

Yes that's correct - if the termination of the vent pipe is within 3m horizontally of an opening window, it needs to terminate 900mm above it.

[dxg]

It might have been an attempt to create some kind of condensation trap. However, they have a outlet at the bottom of the U and either a drain or just an evaporation tray, usually.

[smokey mow]

sugerbear said:

I think I may have found an alternative solution of using an air admittance valve and just doing away with all of the pipe work going into the loftspace.

https://store.jdpipes.co.uk/110mm-air-admittance-v...

Do you have another SVP on the house with an open vent? If not you should avoid an AAV as an option as they only allow air to enter the system (admit) and not leave.