re commissioning a shower

[Deleted User]

My shower is a 2years old and its just started to give a slow flow. Im also having to put in on heat setting2 and number 9 to get a hot water flow. I know someone else who had this shower and theres has a fast flow. Ive heard about recommissioning or restarting your shower so its like a first use. Im not sure how to do it and whether this is true. I got told it lets out the air which may be trapped in the pipes, or the pump? Can anyone shed some light on what or how to do this. Thanks