WC Soil Piping needs sorting :-(

[advisewelcome]

Does anyone know what kind of 110mm connections from the WC can make this piping arrangement (where I can put put a AAV behind a WC stud wall)?...

 

[JohnD]

Is it a concrete floor?

If you hide an AAV behind a wall, it will be a lot if effort to replace it when it jams and stinks the house out (which it will)

 

[advisewelcome]

Is it a concrete floor?

If you hide an AAV behind a wall, it will be a lot if effort to replace it when it jams and stinks the house out (which it will)

Hi, thanks for the reply.

Beneath the WC are quarry tiles, then a small 1cm layer of cement, with loose soil under that (maybe ash substrate).

The AAV could be put behind the WC and behind the white stud wall - with an access hatch for maintenance?

Not sure if I could put the AAV on an upright pipe coming of the 110mm white pipe going into the next room (or if the AAV "has" to be at the start of the water flush inlet??)

Welcome anyone's thoughts - can post up a diagram of what I am trying to do if this is not clear.

 

[JohnD]

Why do you want an AAV? Where is the nearest vent pipe? Where is the nearest external wall?

 

[advisewelcome]

Why do you want an AAV? Where is the nearest vent pipe? Where is the nearest external wall?

Hi, from the WC, which is under the stairs, to man-hole to the side of the property its 3.5m.

There will be a shower room put in the garage room, this will have sink and shower waste connections going into the soil pipe running to the manhole.

The concern has been that the flushing the WC would siphon out from the shower and sink traps and then allow odours.

Hence a AAV should be fitted near the WC to ensure that soil pipe is vented? Do you think its needed?

 

[JohnD]

And where is the nearest vent pipe?

 

[advisewelcome]

And where is the nearest vent pipe?

Hi, the soil pipe goes directly into that WC.

Part of it the soil pipe is underground and then it pops up out of the ground into the garage (where the WC used to be) and then through the wall and into the moved WC.

It has been used like this for the last 6m with no issues.

I was told that if that pipe is not vented - there is more chances of blockages occurring as well (don't know if that is true)?

Also was told that its a 3.5m short run from the WC to the man-hole and thus venting should not be needed (don't know if that is true either)?

The concern is that if new sink and shower wastes are now connected to this soil pipe they may let in odours if water is siphoned out of the traps with WC flushes - the planned shower room is next to the kitchen and if a new small hand sink is also fitted next to the moved WC - these potential odours would surround the kitchen area.

If I go ahead and fit the shower area and sinks and then realise there is a venting issue - everything would have to get ripped up again to accommodate an AAV - hence need to plan for it now, if its needed?

 

[endecotp]

I guess you can avoid siphoning the basin and shower by using a Hepvo or similar waterless trap on them.

I’m unsure whether you need an AAV anyway for the toilet, with that layout. How much drop is there on that 3.5m run?

 

[JohnD]

Where is the nearest vent pipe?

 

[advisewelcome]

I guess you can avoid siphoning the basin and shower by using a Hepvo or similar waterless trap on them.

I’m unsure whether you need an AAV anyway for the toilet, with that layout. How much drop is there on that 3.5m run?

If we said about 2 bricks down where it goes into the floor and about 4 bricks down where it empties into the drain...
130mm going down to 260mm over about 2.5m
As a percentage: 5.2% gradient.

If we said about 3 bricks down where it goes into the floor and about 4 bricks down where it empties into the drain...
195mm going down to 260mm over about 2.5m
As a percentage: 2.6%

I understand most soil pipes are supposed to be 1/40 to 1/110 so that is 0.91% to 2.5% - so we are over the max and therefore good fall?

We could put special traps on the shower and sinks wastes - but if they don't do the job, we got a problem. And it would be better if I install plumbing for a AAV when setting this up, don't have to use it if its not needed - but its there as a pre-caution. Sound reasonable?

 

[advisewelcome]

Where is the nearest vent pipe?

There is soil stack at the back of the house - far away to get to from the front garage. That pipe is plastic at the bottom half and then metal top half. The upstairs WC, sinks, bath and shower wastes connect to it and it goes up in the air and is probably vented at the top - I assume this is the vent pipe you're asking about?

 

[dilalio]

Digging up the garage floor and attaching to the clay pipe lower down is really is going to be a massive faff and I assume raises all sorts of risks if that piping (probs clay piping in old 1940's house) get damaged.

Everyone wants a simple solution, but if that won't work... Guess what!

 

[advisewelcome]

Everyone wants a simple solution, but if that won't work... Guess what!

Thanks. Your re-post is about digging the pipe - its not work-shirking its about risk reduction. We've established by looking through the manhole that the pipe is plastic and it has been dug up already to be inspected.

The question at the moment is should an AAV be fitted when working on the soil pipe height reduction, considering:

- This soil pipe is totally unvented at the moment
- There is 2.6%-5.2% gradient on the pipe over a 2.5m run of it into the manhole
- 2 sinks wastes and 1 shower waste will need to be connected onto it
- If anti-syphoning waste solutions fail - retrofitting an AAV would be hard
- The soil pipe will need some works to lower it in the garage for the shower, so AAV provision could be done at the same time

If the answer is yes, an AAV should be fitted?? - I can then post up some plans for the implementation of an AAV

 

[dilalio]

I'd put one in.
2" should be ok.
As I always say... "it's better to be looking at it than for it!"

 

[advisewelcome]

I'd put one in.
2" should be ok.
As I always say... "it's better to be looking at it than for it!"

Thanks. 50mm or 110mm AAV then.

I understand that it should be... "at least 200 mm above the highest overflow level of appliances on the soil pipe, usually at the top of the vertical stack, vertically oriented, and in an accessible, ventilated location."

Does that mean it "has" to be at the start of the water flush - behind the WC? - or can it be along the soil pipe close to the WC?

Is the key that is has to be before any strap-on waste connections to sinks or showers? - so it can let air in behind the flush and prevent a vacuum following it?