HI, I have a Worcester Bosch combi boiler (Greenstar 30CDi) which seems to work very well, supplies loads of HW to the WHB and kitchen. Problem is we have a Grohtherm 2000 thermostatic shower and bath filler and the lack of pressure means its almost impossible to take a shower under it and it takes 20 minutes to run a bath. I am wondering is it simply a case of we need a pump on the shower? I understand that this is a problem with a combi? Is it likely that there's a fault with the shower valve? When the valve was flushed loads of water came out! Any help would be much appreciated.