I have a shower pump that was stopping and starting constantly and i mean when the shower is off. So i assumed faulty flow switch and replaced the pump, few days later the new pump started doing the same. Both hot and cold from the pump have an air vent fitted and when i vent the air it stops the pump coming on intermittently. I have to unscrew the top of the air vent to release the air would fitting an automatic air vent solve my problem and where could the air be coming from. Also if i shake the pipework around the pump it starts for a second then stops. This one's a tester as i have exactly the same setup next to it powering a 2nd shower and that works fine. HELP!!!! EDIT : Just worked out that it has AAV's already fitted and its the screwtop type. Now the screws are closed down not allowing the air to escape and the pipework is obviously dragging air from somewhere (no leaks been through with fine tooth comb) am i ok to open the screws and just leave them open as i think the impellers movement in the water is causing the formation of air in the system. And why is called an automatic air vent if the air cant escape when you close the bleed screws down lol. They are honeywell AAV's and they recommend to shut the bleed screws after initial bleeding of the sytem. But really am i ok just to leave them open surely they wont leak unless debris gets trapped under the air break!!!