Upstairs toilet & soil stacks

[Bigus Dicus]

I have a similar situation to JMC - I only have a downstairs toilet and I want to add an upstairs one.

Unlike JMC, I think my pipe slope should be OK, but I don't appear to have a "soil stack" visible anywhere outside my house. My mate tells me I must instead have an "air admittance valve" hidden somewhere near my current downstairs toilet (either inside the house or outside under some wooden decking I have). I've never seen it but it definitely isn't upstairs (I have no loft).

If that is true, will there be a problem with the new upstairs toilet? Will I have to move this "air admittance valve" to be higher than the new highest toilet, i.e. the upstairs one?

Does the answer to this depend on whether I have a proper bog or a pumper?

THank You.

[The Natural Philosopher]

Yes, probably.

In essence you need to have a pressure relief system that will carry the pongs away high up SOMEWHERE in the sewer. This may or may not be shared between houses, and it may or may not be visible. In my case I have carried a long exhaust pipe down the length of the roof to exit under the eaves.

Each toilet then needs some way to ensure that as it flushes, the suction of the falling turd and water mix does not suck dry any basin traps etc. That is the purpose of the air admittance valve.

So you need an open exhaust somewhere downstream of every bog to prevent pressure build up, and an inlet somewhat upstream of it, to stop partial vacuums.

Air admittance valves do the latter, but not the former.

[Grunff]

Are you sure about this? This wasn't my understanding at all. The air admittance valve/partial vacuum thing, yes, definitely. Pressure build up? Where is the pressure building up and why? Sewers aren't airtight.

I've seen lots of systems with an air admittance valve and nothing else.

Please expand.

[BillV]

Doesn't every 3rd house or so on a sewer run have to allow air in through a stench pipe? I'm at the end of a cul-de-sac of 5 houses built in 1980. My house has a "stench" pipe through the roof which I wanted to replace with air admittance valve but was advised not to do so but it would be ok for my neighbour to this.

[The Natural Philosopher]

That becuase thay have specail vents to prevent pressure build up.

See your building regs.

Apart from that they are pressure tested to make sure they ARE airtight.

[Bigus Dicus]

Thanks, but I am still a bit confused. If I currently have just one bog, dowstairs, and no soil stack open exhaust above my roof, then presumably:

(a) I have an AAV somewhere in my downstairs bathroom that services only that bog (I am not allowed to take the floorboards up at present as the M-I-L is coming to stay)

(b) Somewhere downstream of my bog there is an open exhaust, although this may be to service multiple bogs in my and my neighbours' houses?

So if I put the new upstairs bog in, I will definitely need another (a) dedicated to the new bog, but the same (b) can service (perhaps) both the new and the old bog, as well as neighbours' bogs?

Please advise - I am VERY confused! Thanks...

[BigWallop]

Sorry I haven't been following the thread, but the jist of the problem is installing another loo in an upstairs room (?) correct. This would depend on where the new loo would be sited to correspond with the original downstairs loo and where the pipework, mainly, for the waste extraction.

Do you have an internal soil stack built in to a corner or behind the plasterwork in the original loo ? Have a look to see where the pipe from the back of the existing loo goes and from there you should be able work out where the soil pipe is in relation to the walls. Does the loo pipe go directly through the wall to the outside. Does it bend and go into a boxed in soil stack in the corner of the room ? Does it disappear through the floor ? When you flush the loo, can you hear the flowing passed in another room beside the loo ?

Once you find out where the existing soil goes you're on your way to being able to makes plans for the new loo. You don't even have to use the existing soil stack pipe if you find out where the sewerage system is in respect to you property. It might be possible, or even easier, to take a new soil pipe from the new loo directly to the sewer system near you house. The pipes are cheap to buy, it's the fitting that cost a bit more in terms of drilling and digging and things.

[Hugo Nebula]

On 13 May 2004 01:41:31 -0700, a particular chimpanzee named [e-mail] (Bigus Dicus) randomly hit the keyboard and produced:

If you only have appliances on the ground floor, and you are in a terrace or close to other houses on a sewer, then you may not have a vent at all. It is acceptable to run a WC (and other fittings) less than 1.5m above the invert into a vented sewer provided the branch is less than 6m long.

If this is the case, then, yes, you would require a new soil stack to the first floor. This could be vented with an air-admittance valve internally. Provided you keep your downstairs WC, you can add a pumped one to the first floor (subject to Peter Parry's approval).