Power shower

[wired]

Recently had a new pump but now after switching on the shower it takes 30 seconds before any water appears and then it is in one heavy downpour for a couple of minutes before becoming a fine spray, any ideas please?

[Disco Fever]

Have you opened all the valves fully or do you have an air lock somewhere....

[wired]

Thanks DF, tried those, seems odd can't fathom it out.