Advice on Air Admittance Valves please

[Paul Cockhill]

Hi

I have a client who has three WC's served by one long waste pipe feeding into a soil pipe.
When the WC on the far left is flushed it causes either one or both of the other WC 's to overflow. I think it must be because an Air Admittance Valve has not been fitted?
Would you agree?
If so what AAV would you recommend and how high a stack pipe should I have
Thanks
Paul

 

[ShaunCorbs]

easy way to test remove the trap to the sink in the top pic

but tbh sounds like a blockage

 

[rpm]

Could equally be a problem within the pipe.

 

[Paul Cockhill]

easy way to test remove the trap to the sink in the top pic

but tbh sounds like a blockage

Thanks. Good idea about the trap to the sink.
The pipe has been checked by dynorod and it is clear

 

[snowhead]

No, I would disagree, It's NOT the lack of AAV or vent (although it should have one or the other.)

It's a blockage, no dispute.
Either between the right hand WC and stack, or lower down the stack or in the ground.

 

[Paul Cockhill]

No, I would disagree, It's NOT the lack of AAV or vent (although it should have one or the other.)

It's a blockage, no dispute.
Either between the right hand WC and stack, or lower down the stack or in the ground.

Thanks. It makes sense to put an AAV on it but they are insistent that the stack is clear. There are toilets in the floor above and they are clearing fine and there is an AAV fitted on that floor

 

[chris watkins]

WC's are all >80mm dia so even if you sick to part H you can have an unventilated 100mm branch up to 15Metres long with up to 8 connection as long as it is laid to a fall of between 9 - 80mm/M.
No requirement for vent or AAAV as float will never run full.

 

[ShaunCorbs]

Thanks. It makes sense to put an AAV on it but they are insistent that the stack is clear. There are toilets in the floor above and they are clearing fine and there is an AAV fitted on that floor

doesnt mean there isnt a blockage in that branch line

 

[snowhead]

The pipe has been checked by Dynorod and it is clear

Not aimed at Dyno-rod specifically, although it includes them, but I've used many different Drains contractors over the last 25 years in 100 + Commercial sites around the Country.
The operative skill level varies from average to downright amateur and ill informed.
Occasionally there's a good one.

The common (incorrect) response in recent years was, It's not a blockage, it needs an AAV.