Shower waste water level

[wozza]

Hi All,

 

When flushing my toilet the water level in the shower drops by about 5mm - it then rises back up and fluctuates up and a down a bit, there does not appear to be any water lost.

 

The end of the soil pipe is sealed. If I remove the seal and fit either a 110mm or 40mm AAV then there is no change - the water still drops about 5 mm then fluctuates up and down for a few seconds - there does not appear to be any water lost. The sink has a Mcalpine anti syphon trap, I have tried with this blanked off as well to see if it makes a difference and it doesnt.

 

I have even tried flushing the loo and pouring a bucket of water into it at the same time, but again the result was the same. 

 

If vent the soil pipe into the room then I do not get any movement in the water levels.

 

So it appears that I do have a very small amount pressure in the pipes when flushing the loo but not enough to activate the AAVs or the anti syphon trap.

 

Do I need to be worried about such a small movement of the water level? Should I vent the pipe to atmosphere or fit an AAV as a precaution (venting to ATM will be a ball ache but do able)

 

Thanks, Wozza.

 

 

 

[Oz07]

Stop worrying

[Temp]

+1

5mm of water is a pretty low pressure change ?