DIY Doctor UK DIY Forums

Hi I am just having installed a pressurized hot water cyclinder using a system boiler.My installer wants to use 15mm pipe to feed two baths after an initial run of say 1meter from the tank of 22mm .i have a feed straight from the water mains nearby that then goes into 22 mm to feed the cylinder why cant we carry that on through to the baths in 22mm .i am thinking that if both baths were filling at the same time it will be slow or at least slower than 22mm.I have seen previous posts but that was assuming using a combi boiler with a 15mm feed , i have a 22mm feed to tank .The reason i am asking is because having now fitted the bath with 15mm pipe the flow seems alot slower than with old system that was gravity fed from a tank in the loft .But i am now using monblock bath taps i dont no if that makes a difference.Also there are two bathrooms back to back in the house coming off of the same 15mm supply & if they are both filling @ the same time then the time to fill a particullar bath doubles from 6 mins to 12mins (big baths 1800x80).Before i reinstall ceiling below & tile etc i did not no if it may be pay me to fit 22mm back to tank .Will it reduce the fill times ?.The mains supply to house is about 20 years old done in 25 mm plastic .Any ideas Many thanks