WC Soil Piping needs sorting :-(

[robinbanks]

I'm certainly not one of those.
And neither is @Hugh Jaleak or @HERTS P&D.

I totally agree (and should have been more clear*/less inflammatory, sorry)

* that it was about the protracted hemming and hawing, probably on multiple forums, with every Joe sticking their two pennorth in leading to perhaps the world's best discussed poopstack

 

[Hugh Jaleak]

I've made several contributions in this matter, we're now on at least Two Threads of multiple pages over the last 12 months and still we're going round in circles as the OP is either unwilling or incapable of taking on board what they are told. I ducked out some time back as I felt I was wasting my time contributing.

I really hope they have a second WC in the property.

 

[robinbanks]

I really hope they have a second WC in the property

This is the best laugh I've had all week!

 

[endecotp]

another AAV when you've already fitted three, and don't have any water filled traps that can have the water sucked out of them, but if you insist, why not boss a HepVO on behind the toilet ?

A Hepvo trap is not an air admittance valve, is it? Have I missed something?

 

[robinbanks]

No, it's not.. But it does. But also you don't need an AAV when your traps are waterless

 

[advisewelcome]

No, because you do a good job of the cut, remove swarf and smooth rough edges, and don't jam the waste so far into the soil that it becomes a catch point. If you look down the bore of the soil it should appear smooth all the way down

You'll note that the the boss built into your existing bend is also on the side, not the top

View attachment 395201

Yes can see how it would be same as a boss connection. I just guess any smaller pipe coming out would always have to go upwards to prevent any soil water going into it.

It would be easier to reprogram your mind to see the lack of necessity for another AAV when you've already fitted three, and don't have any water filled traps that can have the water sucked out of them, but if you insist, why not boss a HepVO on behind the toilet ?

HepVO behind the WC? - would consider it with a bit more info if solves the issues.

The toilet itself also admits air, so the situation is nowhere near as desperate as a multitude of armchair/keyboard warriors may have led you to believe. Why not try without and then fit one after if it turns out there is a problem that needs solving?

Yes, "Fix it and see" - would make sense - the problem is that it does not seem possible to fix the plumbing and then go back to retrospectively fit an AAV without having to redo and disturb things. Its feels easier to make a considered plan and then execute it with the resources (people and all materials) planned to be onsite.

Yeah that would work. Not sure I'd bury the AAV in a wall though

It would be behind a garage stud wall which would hide the current gas pipe, new shower fittings - and the AAV. It can be ventilated and seems like a good idea.


I appreciate your patient feedback. May make sense if I put this altogether into an Outline plan - would indicate the rational, tasks, dependencies, etc and explain the thinking.

 

[advisewelcome]

Outline Plan for New Shower and WC Room Installation

1. Air Admittance Valve (AAV)
○ A 50mm AAV has been indicated as sufficient for ventilation and can be installed behind the new shower stud wall.
○ The stud wall will also conceal new shower piping and the existing gas pipe.
○ The wall will be ventilated and the AAV must remain accessible for maintenance

2. Trap Options
○ AAV fitting allows flexibility to use either water-sealed or waterless traps for both sinks and shower waste.
○ The final traps choice will depend on:
§ Trap orientation and space available
§ Pipe fall and layout feasibility
§ Cleaning & servicing access
§ Which ever option can deal with heavy use

3. Waste & Soil Connections
○ Strap-on connectors can be fitted to the side of the 110mm soil pipe, allowing a 50mm stub stack to branch off at a 45° angle, with the AAV positioned at the top.
○ The WC soil pipe (110mm) may include two 45° bends, depending on angles needed to avoid lifting the existing pantry floor.
○ The WC pan connector will plug directly into this run.

4. Pipe Fall & Flow
○ As long as there is a consistent fall, exact 110mm gradient is not critical due to short run lengths
○ The sink and shower waste pipes will connect into the soil line as shown, maintaining suitable gradients.

5. Alternative 110mm Soil Option
○ The alternative layout involves connecting into the existing brown elbow with a 90° elbow fitting (with boss), running the 110mm soil pipe across the garage floor, below the pantry floor then rising up to the WC.
○ However, this option is more complex — unsure if a flush floor-level connection at the WC would be easy and it requires pantry floor digging.
○ Therefore, the one or two 45° bend option is currently considered simpler.


... assumptions and plan are sound?

 

[dilalio]

Might be easier just to move house

 

[advisewelcome]

Might be easier just to move house

Wish it was. Need a solid plan - will also inform materials needed, only have 1-2 day with resources onsite to make it happen (hence the Anal-retentive planning). I see some things need revision so will post up new plan...

 

[advisewelcome]

Added the worse case plan to run the 110mm pipe straight across...

Revised Plan for New Shower and WC Room Installation

1. Air Admittance Valve (AAV)
○ A 50mm AAV has been indicated as sufficient for ventilation and can be installed behind the new shower stud wall.
○ The stud wall will also conceal new shower hot/cold piping and the existing gas pipe.
○ The wall will be ventilated and the AAV must remain accessible for maintenance

2. Trap Options
○ AAV fitting allows flexibility to use either water-sealed or waterless traps for both sinks and shower waste.
○ The final traps choice will depend on:
§ Trap orientation and space available
§ Pipe fall and layout feasibility
§ Cleaning & servicing access
§ Which ever option can deal with heavy use

3. Waste & Soil Connections
○ Strap-on connectors can be fitted to the side of the 110mm soil pipe, allowing a 50mm stub stack to branch off at a 45° angle, with the AAV positioned at the top.
○ The WC soil pipe (110mm) may include two 45° bends, depending on angles needed to avoid lifting the existing pantry floor.
○ The WC pan connector will plug directly into this run.

4. Pipe Fall & Flow
○ As long as there is a consistent fall, exact 110mm pipe gradient is not critical due to short run lengths (but aim 1:40 and min 1:80)
○ The sink and shower waste pipes will connect into the soil line as shown, maintaining suitable gradients.

5. Alternative 90° elbow 110mm Soil Pipe Option
○ The alternative layout involves connecting into the existing brown elbow with a 90° elbow fitting (with boss), running the 110mm soil pipe across the garage floor, below the pantry floor then rising up to the WC.
○ However, this option is more complex — unsure if a flush floor-level connection at the WC would be easy and it requires pantry floor digging.
○ Therefore, the one or two 45° bend option is currently considered simpler.

6. Worse Case: Alternative Straight 110 mm Soil Pipe Option
○ As last resort, can extend the existing 110 mm soil pipe with a coupler at the current level, using a swept elbow to reach the WC.
○ Include strap-on connections for sink/shower wastes, and AAV stub stack.
○ This option involves the most digging and a new wall opening but offers a direct, simple connection if other routes are impractical.


... this OK? - think I can work out what materials needed to make it happen now?

 

[dilalio]

Fanny traps are OK until they get slimed up with exotic oils from bathing products and exfoliated skin.

Then they need either cleaning or replacing.

 

[advisewelcome]

Fanny traps are OK until they get slimed up with exotic oils from bathing products and exfoliated skin.

Then they need either cleaning or replacing.

Thanks. They didn't mention that in the promo vid.

If a 50 mm AAV is installed, it gives the option to use HepVo waterless traps or standard water traps. HepVo traps could work well on the sinks, since access is easy, but the shower drain may be more awkward to fit and harder to maintain — so I suppose it’s best to keep both options open until the build progresses.

I am not sure if the consensus is that water traps are simpler and more robust, with less maintenance required, so they’re preferred if practical?

Could an approach be to install the 110 mm soil pipe and AAV, connect up sink and shower wastes, then test for siphonage with WC flushing? I assume the sink and shower pipes are usually solvent-welded, so once fitted, they can’t easily be adjusted if changes are needed when the raised stud floor & shower tray need installing?

I guess I need a activity plan with the work put into stages that make sense, permit testing and prevent re-work?

 

[advisewelcome]

Any opinions? Going across the garage floor kinda worked out. 50mm AAV near fan hole for future access. Strap on for sink and shower waste in garage room.

Before you knock it - ensure you was there for me in my time of need

 

[robinbanks]

You'll come to appreciate the strap on..


Good stuff, bit of battening, insulation and plasterboard and it'll all be hidden anyway