Pete you say what your shower pump is but not your shower. Common mistakes with pumps is to place them high in the system because its convenient , but they fill with air. They should preferably be at the lowest point typically the same level as your cylinder. (Air will always rise ). The other common mistake is to take the hot supply from the expansion pipe on top of the cylinder. This can often draw air in from the open vent which you can demonstrate by turning your shower to cold which will flow properly then if you turn it to hot it will bubbly and stutter. If you washing machine is of the old type and draws water from your cylinder this will assist the flow of hot water and your shower may seem to operate okay. Further indication of the hot supply sucking in air. Your shower equipment if using a pump should all be fed from storage tanks and should never be fed from the mains. If your pump is fed via the mains , it will never work properly. Plus I think its a breach of water regs ...... Good Luck
Alan, December 2008
