Hi, my parents had a new hot water cylinder fitted a couple of years ago, they had a large cylinder before it was replaced for a smaller one as suggested by a plumber. This I presume is just the hot water supply as the house is heated with storage heaters. Since this was fitted the pressure in the hot taps is pathetic just a slow trickle. The bathroom and kitchen taps that are mixers is where the problem is, the downstairs WC is fine which has a seperate tap for hot and cold. They have since had the plumber back about a year ago who thought it could be an airlock but could not find anything(I think he was a friend of a friend). Please help as they have now been putting up with it for 2 years but are both too stubborn to sort it out. Is it a diy job or more one for the pro's.
The "head" is the vertical distance between the top of the water level in the CW storage tank in the roofspace and the highest part of the tap. For a bathroom if that is iro 2m then you will get about 0.2 - 0.25 bar pressure which should be adequate for most taps even the modern ceramic disc type although it's probably right on the limit.
Are any of the valves that should be open, in fact, shut? Specifically I'm thinking of the gate valve that should be fitted in the pipe which feeds cold water from the CW storage tank in the roof to the bottom of the HW storage cylinder.
The fact that they've put up with it for a further year after "the plumber thought it might have been an airlock" says that the answer to your question: "Is it a diy job or more one for the pro's" is the latter.
Given the time this has been going on this has got to be a better solution than requesting "site unseen" advice here frankly. Not being obstructive - just seems sesnsible.