Boost Hot Water Pressure

[mardyfish]

I want to boost hot water pressure to a thermostatic bath/shower mixer tap.
Hot water supplied by a vented hot water cylinder. cold supply is mains fed.
Have been told by another plumber that the easiest way is to fit a single impeller pump, and fit it in the cold water supply pipe from the CWST. So that the water is drawn from the CWST and then pumped into the bottom of the cylinder. Has anyone tried this? will it work?

 

[ecowarm]

Both hot and cold must come from a cistern and then a twin impeller pump could be fitted, you would need somebody to look at this though

 

[ecowarm]

Welcome to the forum

 

[Best]

Think you have mistaken what the plumber meant, - or else he is not a plumber! That would be pressurising the vented cylinder!

 

[mardyfish]

O.k i take your point, so what is the easiest way to boost hot water pressure?
Can I fit surrey flange to top of the cylinder and use the take off from this to the pump and connect pump to hot feed to the taps?

 

[Dorset Plumber]

Most if not all thermostatic bath/shower mixers require balanced water pressures.
Your best bet is to contact a plumber in your area and ask him to install a twin impeller pump, run it direct to the mixer.
Stay away from the 1.5 pumps, you need a good 2.0 bar pump for high pressure.

 

[mardyfish]

Thanks for all the replies, it seems a twin impeller pump is needed. I just thought there might be an easier way than piping both hot and cold to the mixer tap, but it's not sounding like it.

 

[Alanka]

You can boost just the hot water if you want to, provided you fit the right pump in the right position.

I fitted a New Team 'Varispeed' 50 Single Pump (Vari Si) in the hot water supply pipe coming from the vented hot water cylinder in a flat, where the cold was mains. The cistern supplying the cylinder was big enough to cope with the resulting increased flow. This of course boosted all hot water outlets in the flat, not just the bath mixer -- but having balanced h and c water throughout was an advantage, not a problem, for the tenants. The shower, especially, then worked brilliantly.

This particular pump has an adjustable speed control, so I was able to balance the hot water pressure to approximately equal the cold mains -- the ideal situation. To comply with backflow regulations I fitted non-return valves to the hot and cold feeds to the bath mixer and the shower. This prevented any of the mixed waters flowing back into the mains supply, in the event of loss of mains pressure or for any other reason.