pumping hot water

[soccercoaching.advice]

The pressure of the hot water supply to all the taps in my house is very low. The cold water pressure is fine.

I'm thinking of installing a pump on the outlet of my indirect hot water cylinder.

Presumably, I need to fit a gate valve above the pump so it can be isolated. Is this correct?

Also, before I cut the 22mm outlet pipe from the cylinder, do I need to drain all the hot water off or is it sufficient to simply turn off the cold feed to the cylinder (on the basis that it's the pressure of the cold water that forces the hot water out when a tap is turned on)

Any other tips or advice on fitting the pump would be much appreciated.

Thanks.

[soccercoaching.advice]

One more thing...do I need to put a Surrey flange into the cylinder?

[robgraham]

This is an identical query to one only a few threads lower down which has very fully discussed this -

"low pressure problem - please help!"

The essence of that thread is that if the pressure is low to all taps then the problem will not be solved by a pump as either the feed to the HW tank or the main outlet is restricted - you cannot increase the pressure if the volume is not there.

Rob

[soccercoaching.advice]

What sort of problem with the feed to the hot water cylinder could there be?

A faulty gate valve restricting the flow into the cylinder?

Or could there be an internal problem with the cyclinder?

[Rob Morley]

I only skimmed that thread, but saw no evidence of this - where's the bit that says a hot water booster pump won't work?

[robgraham]

More pressure means more total volume - agreed ?

More total volume means that there has to be greater flow in the pipes to the shower / taps - OK?

It also means that there has to be more volume of water through the HW tank - still with me ?

And correspondingly that means there has to be a greater volume into the HW tank from the Cold Water tank in the attic.

Ergo if any of these isn't up the flow required, the pump is not going to do what is wanted and will draw water from the vent pipe until it is sucking air, cavitates and damages itself. A pump will ony make a difference if the volume flow is all OK and the problem is lack of head

- that is the CW tank is not high enough above the shower/taps.

Skimming the thread on "low pressure problem" would probably miss the clarity of that point.

The pump is not a panacea for low pressure - the cause of the low pressure has to be ascertained first and corrected.

I live in a single storey cottage - the head is 4 metres (0.4 bar) which probably cannot be bettered in a single story property, and I get plenty of volume at all my HW taps because I used a 28mm feed to the tank and 22mm thereafter. It is not however enough for a shower where a minimum of 1 bar is desirable so currently I have an electric one.

I've probably given enough above to assist Supercoaching to work through his problem though if he is in a hard water area that's another matter as his HW pipes could be furred. The HW tank itself is very unlikely to be the source of the problem as it is really just an extremely large diameter pipe in the route from the cold water tank !

Rob