Need to fix Soil Stack Venting through attic

fran426ft

TLDR: look at panorama photo....bad I know right:o. How best to fix it?

So following sonny liston's recent thread on extractor fan venting through his attic I thought I better ask for advice on my soil stack venting (I'll worry about extractor venting which is equally bad later:(). I knew it was a sh1te job the way it is but mostly ignored it since we move into the house 3 years ago as it's easy to ignore things in the attic. The house is around 14 years old.

I've attached some photos to show the state of it. The panorama image gives the best idea of what I'm dealing with.

There are two soil stacks in the house one at the front (left of the panorama) and one at the back (right in the image). Both vent into the attic where the pipe is connected to white flexible ducting. These ducts then take a long path towards one end of the attic and up to some roof vents near the apex at the back of the house. There they are just jammed into the vents and held poorly with some duct tape. The ducting is held in place in a few places with cable ties and sags in multiple spots due to the long lengths.

When I had a look at it today the duct that goes to the bathrooms we use most had several litres of condensation trapped in one of the sags and the duct had pulled away from the roof vent so it was just venting into the attic.

So based on this can anyone offer suggestions about how best to correct it? Should I just hard pipes it ensuring no low spots and either adapt to the existing roof vents or have a roofer replace them with ones I can connect to. Would it be acceptable to tee the two lines together to a single roof vent? Is it even acceptable to have the runs so long or should I be looking into getting new vent tile installed closer to the top of each stack. I’d prefer not to have to put one at the front of the house just for aesthetics but these current path across the attic is ridiculous.

The back of the roof vents have a strange profile on them. Rectangular about 6” wide x 3.5” high with chamfered corners. I expect it would need a special adapter but I can’t find anything like it online. Also one of these two roof vents is partly blocked by a truss so not full accessible to connect to with the correct adapter anyway. There are two other roof vents in the attic at the opposite side of the house which would result in a similar scenario, again one half blocked.

sonny liston

I was reading today about Air Admittance Valves, or Durco valves.
Allow air in, but not nasty fumes out. In theory you could replace those flexible hoses in the attic with AAV valves.
Maybe someone with more expertise could comment.....

loyatemu

why are they going into the attic at all if they're on the front and back of the house? They should carry on directly up past the eaves and vent into the open air.

fran426ft

loyatemu wrote: »

why are they going into the attic at all if they're on the front and back of the house? They should carry on directly up past the eaves and vent into the open air.

Sorry I may not have made it clear. The stacks are internal to the house, not external on the walls. If they were external yes it would make sense to bring it past the eaves and vent externally.

From what I'm reading I should probably be looking at air admittance valves as sonny mentioned.

fran426ft

Reading Building Regulations Part H it says:

1.2.3.8 Ventilated discharge stacks may be terminated inside a building when fitted with air admittance valves complying with I.S. EN 12380 Air admittance valves for drainage systems - Requirements, test methods and evaluation of conformity. Where these valves are used they should not adversely affect the amount of ventilation necessary for the below ground system which is normally provided by open stacks of the drainage pipework. Air admittance valves should be located in areas which have adequate ventilation, should be accessible for maintenance and should be removable to give access for clearance of blockages. Air admittance valves should not be used outside buildings or in dust laden atmospheres.

The part I'm not clear on is can I just cap off the two soil stacks with an air admittance valves or must there be some other point of ventilation in the stack if I do that? Any diagrams I've seen with AAV's just seem to have them popped on top so they would suggest that's acceptable but how do I ensure that does "not adversely affect the amount of ventilation necessary for the below ground system"

Also would a loft be considered a dust laden environment with particles from the insulation? I assume not.

dathi

https://www.designingbuildings.co.uk/wiki/File:Soilventpipe.jpg

do you have a pipe like this running on outside of house

fran426ft

dathi wrote: »

https://www.designingbuildings.co.uk/wiki/File:Soilventpipe.jpg

do you have a pipe like this running on outside of house

No the soil stacks are internal, boxed in and run up into the attic. Similar to what's shown in the second paragraph of this link http://www.draindomain.com/soil%20vent%20pipe.html
It shows an air admittance valve on top which is what I think I'm going to fit on the two soil stacks.

antoinolachtnai

There are two problems here. 1. Venting the drainage system generally including the underground sewer. Sewer systems must be vented or Bad Things could happen. 2. Avoiding vacuums which impede water flow.

Solving number 2 using an AAV doesn’t mean you can forget about 1! If your neighbour is well vented and there isn’t some sort of trap between you you will be fine, but you can’t rely on that. Maybe it would be ok to put an air admittance valve on one stack and a vent on the other, it depends on how the overall system is put together. Also, it might be better to find a place to put the AAV inside the building envelope to avoid any risk of freezing (I.e., put it on the soil pipe or s as connected pipe near a toilet or sink)

An idea might be to run the vent in a smaller pipe. It doesn’t have to be 4-inch.

fran426ft

antoinolachtnai wrote: »

There are two problems here. 1. Venting the drainage system generally including the underground sewer. Sewer systems must be vented or Bad Things could happen. 2. Avoiding vacuums which impede water flow.

Solving number 2 doesn’t mean you can forget about 1! If your neighbour is well vented and there isn’t some sort of trap between you you will be fine, but you can’t rely on that. Maybe it would be ok to put an air admittance valve on one stack and a vent on the other, it depends on how the overall system is put together.

An idea might be to run the vent in a smaller pipe. It doesn’t have to be 4-inch.

The house is detached with waste line separate from neighbors. The two soil stacks only connect via the underground waste pipe, one connecting at the front of the house and the other at the back. The underground waste pipe goes right around the house, except one side. The gutter downpipe drains also connect to the same underground waste pipe I believe. I may be wrong, but I don't think the gutter drains have traps on them. If that's the case they would certainly vent the underground waste pipes. I'll need to check if there are traps on them but that may solve the venting concern.

EDIT: I'm probably wrong on the lack of a trap on the down pipe drains as building regs say they must be there for combined waste systems.

antoinolachtnai

fran426ft wrote: »

The house is detached with waste line separate from neighbors. The two soil stacks only connect via the underground waste pipe, one connecting at the front of the house and the other at the back. The underground waste pipe goes right around the house, except one side. The gutter downpipe drains also connect to the same underground waste pipe I believe. I may be wrong, but I don't think the gutter drains have traps on them. If that's the case they would certainly vent the underground waste pipes. I'll need to check if there are traps on them but that may solve the venting concern.

The gutters should feed into a trap and should ideally link into the storm water system not the sewage system. You can’t, or at least shouldn’t, rely on the gutters as vents. It might just work, but it would be very poor practice.

If the two stacks are linked underground that might mean that just one vent would be ok.

fran426ft

These are the two pipes coming into the attic. I will probably need to remove the 135deg bends, and use some elbows and straights to bring the pipe away from the roof so I can get it up above the insulation and standing vertically so the AAV will work if I fit it. Hopefully the existing bends are just push on fittings instead of solvent welded so they just pop off.

dathi

yes an air admittance valve should work but if it was my home i would be installing a new tile/slate vent close to the stack and connecting to it with wavin

sonny liston

dathi wrote: »

yes an air admittance valve should work but if it was my home i would be installing a new tile/slate vent close to the stack and connecting to it with wavin

I'm curious why you would prefer the extra cost & labour of adding a new tile vent, and breaking the roof seal increasing the risks of future leaks, over an AAV?


Cheers.

The Continental Op

Sorry OP can you clear this up for me? Are those really soil stacks and not attached to extractor fans?

fran426ft

The Continental Op wrote: »

Sorry OP can you clear this up for me? Are those really soil stacks and not attached to extractor fans?

Yes they are soil stacks.

The extractor fans are connected to similar ducting (uninsulated) which are just run over to the eaves. Except one duct from our spare bedroom ensuite which I found just lying next to the extractor fan under the insulation because the extractor fans was installed where there is a truss. They even notched the truss to make it fit. As I said in the OP extractors are as bad a mess.

loyatemu

sonny liston wrote: »

I'm curious why you would prefer the extra cost & labour of adding a new tile vent, and breaking the roof seal increasing the risks of future leaks, over an AAV?


Cheers.

isn't the main purpose of the soil vent to allow gases out of the sewer. I'd rather not have those going into my attic.

fran426ft

loyatemu wrote: »

isn't the main purpose of the soil vent to allow gases out of the sewer. I'd rather not have those going into my attic.

Not necessarily, if fitted with a air admittance valve it is only to let air into the system to prevent a vacuum from occurring and sucking traps dry from sinks toilets etc. The air admittance valve is a one way valve so should prevent gas entering the attic.
That said from read the building regs the system should be vented somewhere. What had me confused is nothing else online mentioning this when they show AAV's being used.
The building regs state:

1.2.3.8 Ventilated discharge stacks may be terminated inside a building when fitted with air admittance valves complying with I.S. EN 12380 Air admittance valves for drainage systems - Requirements, test methods and
evaluation of conformity

However they then go on to state:

Where these valves are used they should not adversely affect the amount of ventilation necessary for the below ground system which is normally provided by open stacks of the drainage pipework.

further on for the under ground system it states:

1.3.2.2 The system should be ventilated by a flow of air. A ventilating pipe (without an air admittance valve) should be provided, at or near the head of each main drain, to any branch longer than 6 m and on a drain fitted with an intercepting trap (particularly on a sealed system). Ventilated discharge stacks may be used (see paragraphs 1.2.3.4 and 1.2.3.5).

So my reading is air admittance valve can be used, but if they are, an alternative method of venting the underground system should be present. Based on this what I'm likely to do is fit an AAV on the soil stack towards the front of the house and try to sort proper venting for the one towards the back of the house. The one at the back of the house would then allow for the venting of the underground system as it's at the head of the system anyway. I don't fancy fitting a vent in my back garden and it's more awkward to properly terminate the stack at the front of the house to an open vent so I feel this is a reasonable compromise that should still meet the recommendations of the building regs.

(side note: the building reg technical guideline document uses "should" when referring to venting of underground systems. From my experience reviewing standard within different regulated industries this would be interpreted as a best practice/recommendation and not a mandatory requirement.)

dathi

fran426ft wrote: »

(side note: the building reg technical guideline document uses "should" when referring to venting of underground systems. From my experience reviewing standard within different regulated industries this would be interpreted as a best practice/recommendation and not a mandatory requirement.)

the building regulation is the mandatory requirement (the bit in blue box) the TGDs show you the prima facia way of complying with the regulation how ever if you deviate from the TGDs it is up to you /engineer to prove compliance

fran426ft

True and Part H actually has very little in it in terms of mandatory requirements for a drainage systems:

(1) A building shall be provided with such a drainage system as may be necessary for the hygienic and adequate disposal of foul wastewater from the building.
(2) A building shall be provided with such a drainage system as may be necessary for the adequate disposal of surface water from the building.
(3) No part of a drainage system conveying foul wastewater shall be connected to a sewer reserved for surface water and no part of a drainage system conveying surface water shall be connected to a sewer reserved for foul wastewater

To be clear I don't plan on deviating from the TGD. My proposal still meets the recommendations of the TGD which allows an AAV. I will also vent at the second stack to comply with the venting recommendation.