Solving Stack Issue - Opinions Sought - Not Simple

[SirLancelot]

Hello fellow members:

Situation: This "stump" stack pipe is just outside the downstairs bathroom.

There is a sewer smell inside the house most mornings.

Suspicion: it's something to do with the stumpy stack pipe.

Actions: The vent valve on-top, was taken off. It was full of debris & therefore stuck shut.

I cleared debris and wedged open the valve with a small piece of wood.

Next few mornings, the sewer smell disappeared.

I think the smell was drawn into the house, thorough the vents (suspended floor) which have been temporarily blocked, with a rectangular piece of acrylic board (you can see in some of the pics).

I'm hoping extending the stack over the roofline (like the white stack) will permanently solve the problem.

Help: I would like the job done properly and with due consideration to regs. I am going to install the stack myself (broke), and I could use the communities help in explaining what I would need to do, what clearances I need to keep & what considerations have to be taken into account.

I am a fellow long term member and I'm asking for your input.

My thanks to any willing to contribute.

SL

 

[Exedon]

Extending stack to a similar high as your existing would certainly solve problem
But I would try changing existing air admittance valve for a new one that's intended for external use.

 

[danfre]

If you are going to extend the stack
use 2 x 45 degree bends to the right then go straight up and use 2 more bends around the soffit. The pipe should extend 900mm above the window

 

[Hugh Jaleak]

What you have on the top is an Air Admittance Valve, (AAV), which is designed to allow air into the Drainage system when required, but not allow positive pressure out. There is already another Vent stack on nearby on the property, which should be ample for suitably ventilating the drains, (providing they are all on the same run, and I'd be extremely surprised if they aren't.)

Wedging it open obviously means it acts as a vent, and allows positive pressure out, but in this instance you need to be looking as to why positive pressure is being created. Replacing the AAV with a Stack will only sure the symptoms not the problem.

It looks rather like the original Ground floor WC connection was taken across to the Cast Stack, and at some point since, this has been altered and the Stub Sack installed, connected directly into the underground run, (the reinstatement is clearly visible in the concrete.) I would be confident in saying, that is where the issue lies. The underground section may be on a backfall or have a 'belly' in the pipe where waste is collecting, causing a partial or full blockage, which leads to air struggling to be displaced when the Ground Floor WC is flushed.

I would get the drains CCTV surveyed first, and see what that shows up.