I have had two power showers in my home for 10 years. After recent heavy use (all the bridesmaids) they both packed in. One burnt out the printed circuit. the other just gave up the ghost. Fitted new one and replaced the circuit board in the other. Now they are both suffering from air in the pipes. When I disconnect the pipes from the showers and run the water through hot and cold pipes the problem goes the shower works for one day and then needs to be re-drained. Has anyone any idea what is causing this. I have tried fitting a tap on each of the long pipe runs to drain off the air to no value. If I fit air traps (which one should I choose) will this solve the problem and how did it suddenly appear after ten years