Poor flow of hot water in bath

[Cylonmaster]

The hot & cold pipes to my bath are 15mm, shouldn't they be 21mm. The hot water is feed from a hot water tank and is a dribble whilst the cold is very strong. Should I have the pipes changed to 21mm or would an electric pump on the hot water feed suffice? If fitting a pump, are they robust and how long should they last before being renewed?
As a plumber finding this in your house, what would you do?

 

[ShaunCorbs]

Is the tank feeding the hot water in the loft or ontop of the cylinder?

 

[Deleted member 120897]

Are you referring to a vented cylinder or unvented? If vented then absolutely, the pipes should be larger bore, as it’s typically low pressure. If you have an unvented hot water cylinder then 15mm should be ok as it should be equal to your incoming main or pressure reduced if quite high.

 

[Cylonmaster]

Hi, the hot water comes from the top of the hot water cylinder. The cylinder was with the house when bought 15 years ago so I expect it'll be vented. Would a pump suffice or is it a strip out and re-plumb?

 

[Cylonmaster]

Or would fitting a non vented cylinder solve the problem?

 

[Deleted member 120897]

There seems to be some guesswork here. Are you able to upload some photos of cylinder?

 

[Cylonmaster]

The pictures show the tank and the pipework to the bath. This was put in by a plumber who said it's the taps that are causing the problem. The feeder pipes rising from the floor aren't the original pipes

 

[ShaunCorbs]

Would get rid of them valves attached to the pipework that comes out the floor your flow should be a lot better with them removed

 

[Deleted member 120897]

Thanks for photos. You have a vented cylinder, above this somewhere will be a cold water storage cistern, which the higher up it is, the better the pressure and equally flow rate. Hard to tell, but there appears to be a gate valve or 2 on the hot water from the top of the cylinder, which if not fully open, will restrict the flow. I would also be inclined to replace the hot pipe for 22mm for decent flow rate, and I would also have it separated from touching the cold pipe to prevent undue warming (water regulations).

 

[Cylonmaster]

So is an electric pump not a good option on the hot water supply? Changing the pipe will probably require the bath out and flooring lifted etc.