Loss of hot water pressure

[Corazones]

Can anyone please advise on this? I have a flat which has just been extensively modernised, since when the hot water flow at the kitchen tap has reduced to a trickle.

It is an upper floor flat and the (unpressurised) water supply consists of a cold water tank with ballcock valve, immediately above the hot water cylinder. These sit on the floor and so the head of water is not great, but before conversion the flow was acceptable.

However, now that a modern s/s sink with mixer tap has been fitted, the flow is inadequate. There is only one hole in the sink and so two separate taps are not an option. A plumber suggested that the small-bore fittings for the two flexible hoses into the bottom of the taps, combined with new isolating valves which may not be full-bore, could be responsible.

Can anyone suggest a type of mixer tap which might give a greater flow, or any other solution other than (a) fitting a new sink unit with two holes, or (b) fitting an automatic pump on the hot supply coming from the cylinder, neither of which is really practical for various reasons?

Many thanks,
Alec.

 

[Madrab]

Cold water tank moved to the attic space? Very little you can do about the pipes feeding the monobloc, the valves could be changed for full bore valves though. The plumber who fitted it should be giving you a reason why the flow has reduced. If the only thing that has changed is the tap type, i'd also check whether the mixer tap fitted is a low pressure type and not a high pressure one.

 

[Corazones]

Thanks, Rob - that's a couple of possibilities which had not occurred to me.
Alec.

 

[Corazones]

Further to the above, I have come across an "ultra low pressure mono kitchen sink mixer tap, which works on 0.2 bar". Fitting that, plus changing the isolating valves, might be the best solution, do you think?
Alternatively, the loft trapdoor isn't big enough to move the cold water tank. Would it be possible to fit a small header tank up there, without converting the original cold water tank to a sealed type? If the original ball cock had an extended feed pipe into the original tank, would the pressure not effectively increase to the higher level once the header tank switched itself in? I can't quite get my mind around that one.
Alec