air admittance valves

west_ham_till_i_die

I have a downstairs bathroom with the toilet feeding straght into the soil pipe at ground level and the bath and sink going to a gully outside.

Now I am puting in a new bathroom above the old one i will need to put in a new stack I want to use a Waste Manifold so that i can run all pipes between the joists.

What I don't want is for the stack to enter the new bathroom.

But what about a air admittance valves do I need one if so why as I have read If it's the only vented soil pipe in the house then you can't install an air admittance valve

keystone

west_ham_till_i_die wrote: »

I have a downstairs bathroom with the toilet feeding straght into the soil pipe at ground level and the bath and sink going to a gully outside.

Now I am puting in a new bathroom above the old one i will need to put in a new stack I want to use a Waste Manifold so that i can run all pipes between the joists.

What I don't want is for the stack to enter the new bathroom.

But what about a air admittance valves do I need one if so why as I have read If it's the only vented soil pipe in the house then you can't install an air admittance valve

Quite correct. You must (Bldg Regs) have at least one open vent on your system but why would you need an AAV anyway. If your existing downstairs bathroom has a vented stack surely that goes straight up either outside or internally through where the new bathroom is to go. You connect the new bathroom to that stack You cannot remove the dry (vent) portion and fit an AAV. Or am I misunderstanding what you are saying?

Cheers

west_ham_till_i_die

There is no stack at all outside or inside the toilet connects at ground level at the moment

keystone

west_ham_till_i_die wrote: »

There is no stack at all outside or inside the toilet connects at ground level at the moment

OK so you must have another stack somewhere? How does downstairs vent at present? In any event if you're going to have a 4" soil pipe from the new bathroom going down to join the current soil outlet yes you will need an AAV in your new bathroom and I'm afraid the stack will have to protrude into the bathroom because the AAV will need to be higher than the basin trap.

Cheers

west_ham_till_i_die

Its a 1930 cottage I dont have any stacks at all there are no vents I was going to remove the old toilet and connect a new soil pipe to the new toilet upstairs as there is no vents at the present why do i need to add one

keystone

Because you are going to add between 8 and 10 feet of vertical drop from the outlet of your WC to the underground element of the drain, As you will be using a manifold all your wastes will connect there and when you flush the loo 6 litres of water plus other unmentionables will rush down that drop. This will create a partial vacuum above it. The only way that will be relieved if its a closed pipe as you are proposing will be by syphoning the water out of the bath / shower, basin and possibly WC traps thus permitting the smells from the sewer to revisit your nice new bathroom. Standard anti-syphon traps in basin etc won't help. The pressure exerted down the 4" soil pipe will be too great. So you'll need an AAV.

You don't have that drop at present so you don't have the problem.

Thats how it is but as you don't have a vent currently perhaps you should blow in the ear of your friendly local BCO and see what they say.

Cheers

beetlebum_2

Interesting post keystone. I guess this explains why my mother's bungalow doesn't have a vented stack. I did wonder why.

west_ham_till_i_die

Thanks Keystone for your help,
I am going to have to enter the new bathroom with a AAV set at the hight of the basin, as I am using a Waste Manifold could I fit a 32mm AAV to one of the 4 inlets as this would look better then having a 4" stack pipe in the bathroom

Canucklehead

Hi

Here you go ,design your own system!

If you fit an AAV make sure it terminates above the basin ie: above the flood level.


GSR.

keystone

west_ham_till_i_die wrote: »

Thanks Keystone for your help,

Pleasure.

I am going to have to enter the new bathroom with a AAV set at the hight of the basin,

No it must be above as I said in an earlier post and as CH has reaffirmed.

as I am using a Waste Manifold could I fit a 32mm AAV to one of the 4 inlets as this would look better then having a 4" stack pipe in the bathroom

Then surely you'll have the waste manifold in the bathroom?

I really think you should have a chat with the BCO like I said last night. On reflection I think you'd be far better off with a 4" core drill (and a couple of smaller sizes), make appropriate holes in the wall and create yourself an external stack with a vent above roof level. You'll have to join up with the existing foul water drainage which means digging and as it will be a new connection you'll need Bldg Regs so you'll have to talk to the BCO anyway.

Cheers