Persistent air issue in pipework through loft

[Sid Viscous]

Evening chaps, I'm having a bit of a mare with a pumped shower I fitted a few months back. The customer had an existing gravity shower fitted & wanted a pump fitting. I put an RP75PT in the loft on the original pipework, a Surry flange on the cylinder and AAVs on the positive side of the pump. However there's still air getting into the hot pipe. There is a manual vent on the hot where it comes up into the loft and this has to be released roughly weekly. Does anyone know if one can fit an AAV on the negative side of the pump or is this going to 'suck' in more air & make it worse? (The flange is deffo piped up correctly before you ask, I double checked!)
Thanks in advance,
Seasons greetings,
Stay safe!

 

[exedon2]

When fitted in loft salamander recommend using a stopless Essex flange and a 400mm anti gravity loop
Is there 600 mm from pump to tank base?

 

[Sid Viscous]

When fitted in loft salamander recommend using a stopless Essex flange and a 400mm anti gravity loop
Is there 600 mm from pump to tank base?

There is, yes

 

[Davey123]

When fitted in loft salamander recommend using a stopless Essex flange and a 400mm anti gravity loop
Is there 600 mm from pump to tank base?

Think I am right in advising that air vents should not be installed on shower pump pipework.