Boiler water pipe routing and air locks

[csauk]

Hi
I'm installing the pipework for my conventional open-vented fully-pumped system. The route of the downstairs boiler flow/return pipes needs to cross some existing gas and water pipes. Does anybody know if it would cause air-lock problems if I dipped the flow and return under the existing pipes giving a drop in level of only 1 inch?
Thanks for any assistance.

 

[ChrisR]

It won't cause any trouble

 

[csauk]

Thanks Chris - That's very good news. Cheers

 

[lor]

OPEN VENT MUST RISE ALL THE WAY TO THE F & E

 

[csauk]

Hi Lor - It would rise all the way except for the 1 inch dip - Are you saying that will cause problems?