32mm Vent.

[Simon Smith]

I have a cloakroom toilet that isn't connected to an outside vent. It's been there 100 years and I don't think it has ever been vented. The floor and wooden paneling were rotten and I ripped them out a long time ago when we bought the house, without ever using that toilet so I don't know if it creates a vacuum when flushed. I now want to replace the toilet and my question is will it need to be vented and if so is a 32mm air admittance valve sufficient for a toilet or is that size just suitable for a sink? The other toilets in the house are all vented through an external stack but this one isn't connected to the others. Thanks.

 

[Deleted member 120897]

If the others are connected to a stack, I wouldn’t have thought additional would be required.

 

[Simon Smith]

If the others are connected to a stack, I wouldn’t have thought additional would be required.

Thanks but the one in question isn't connected to the others in any way.

 

[Deleted member 120897]

Thanks but the one in question isn't connected to the others in any way.

So it’s a separate sewer system?

 

[exedon2]

So assuming it's connected into a inspection chamber and the drains are correctly vented at highest point should be fine.

 

[Simon Smith]

So it’s a separate sewer system?

 

[Simon Smith]

No, not seperate system. I guess they all meet somewhere but I'm not certain where. It's a 120 year old building with a couple of more modern extensions and the drainage system is a bit of a mystery in places.

 

[Simon Smith]

So assuming it's connected into a inspection chamber and the drains are correctly vented at highest point should be fine.

Thanks.. that toilet doesn't run into an inspection chamber. I'm o.k. with adding an indoor vent but my question is really "is the 32mm vent sufficient for a toilet or is it only used on a sink". Cheers.

 

[exedon2]

Could really do with a sketch of how you think drains run with approximate distances and direction of fall also pic of what you have inside? Do you intend having a wash hand basin in cloakroom if so how do you intend running waste?

 

[Basher]

my question is really "is the 32mm vent sufficient for a toilet or is it only used on a sink". Cheers.

Hi Simon
The reason you haven't had a quick yes/no answer is that it depends, strictly speaking, on how the flow calculations come out. There's not enough information on pipe sizes, lengths, bends and the relative heights involved, and I'm not competent to do them anyway!
But as a general rule of thumb, where a wc is part of the equation, 75mm and upwards seems to be recommended for an AAV.

There's Guidance from BPF Group https://www.bpfpipesgroup.com/media/29598/Air-admittance-valves-for-domestic-properties.pdf
that says:
Renovations and Property Alterations
AAVs can be installed on stub stacks. This presents a useful access point, but care should be taken to ensure that the AAV is accessible and that any boxing is vented.
On the ground floor, a separate group of appliances (e.g. cloakroom) may be connected to a drain using an unventilated stub stack.
An AAV is not required if the vertical drop from the centre line of the WC branch to the invert level of the drain is no more than 1.5 m and the centre line of the highest appliance is no more than 2.5 m to the level invert of the drain. However, where stub stacks discharge directly to a drain, the head of the drain should be ventilated. (Which you're saying it is)
AAVs are widely used on stub stacks to avoid any doubt about ventilation and to provide a convenient access point for maintenance.