Is there something (presumably some kind of acid) that I can use tos flush my hot water system to rid it of chalk which is blocking the flow?

Greybeard, November 2009

Hi
The chalk that you refer to is probably soft limescale do not add any kind of acid to your water system as it may attack soldered joints etc . heres a link that might help if you have a combl boiler
http://www.pflush.com/combi-boiler-descale.html

Graham, November 2009