Posted by: @spanners

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My question is that after the heat pump has been installed, will my domestic hot and cold water still be at 7.5 Bar and if so, what would be the best way the reduce the pressure (and maybe equalise the pressures between the hot and cold water if needed) and also where would be the best place be to install any water pressure reducing or equalising valves that are needed?

The new installation will come with a pressure limiter which will limit the water pressure on all hot outlets and any cold outlets which were previously 'indirect' (ie fed from a tank in the loft) to 3 bar.  This works just great for a shower.

Alternatively it is possible to install a pressure limiter on the incoming mains.  

Hope that helps.

Posted by: @spanners

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When I had my heat pump survey the guy said that my water mains pressure was 7.5 Bar which I thought was pretty high, when looking at the specs for the mixer shower I am intending to install, it states that the water pressure to the shower is recommend to be between 2.5 and 3.4 Bar.

7.5 bar… Bloody hell. That’s not mains pressure, that’s a fire hose 😂

You could probably jet-wash your driveway with that. 

@Mars I know, unless the surveyor guy was mistaken?  I might just double check it with a gauge to be sure.

Posted by: @spanners

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@Mars I know, unless the surveyor guy was mistaken?  I might just double check it with a gauge to be sure.

He may well be right.  I have 9 bar which, on one occasion, burst open a steel radiator (with a bit of help from my stupidity).

Mixer showers need virtually identical hot and cold pressures (or at least our new one did) or you need a high flow to mix properly. Our mains varies from 1.5bar (very poor, they suffer at the top of the hill) to 4 normally. Our retrospectively fitted pressure reducing valve is on the output of the water softener, usually set about 2 bar.

Posted by: @judith

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Mixer showers need virtually identical hot and cold pressures (or at least our new one did) or you need a high flow to mix properly. Our mains varies from 1.5bar (very poor, they suffer at the top of the hill) to 4 normally. Our retrospectively fitted pressure reducing valve is on the output of the water softener, usually set about 2 bar.

Agree.  Fortunately UVC installations (which almost always are included with an ASHP) include a pressure reducing/balancing valve to supply cold water to the former 'indirect' circuit (if there was one) at the same pressure as the hot water from the tank thus sorting this out, assuming your plumber knows what he is doing!  Both hot and cold for the mixing shower need to be supplied from this valve.  Many times your plumbing will be such that this is automatically the case, but this isn't guaranteed unless checked because plumbing can be weird and wonderful if 'added to' at various times.  This sort of thing is part of a competent ASHP install.

Posted by: @spanners

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My Daikin hot water tank will be on the ground floor and my mixer shower will be on the first floor.

Just note that this will yield a reduction in pressure of about one-third Bar between the DHW tank and the shower.

1 Bar is about 10 metres head of water.

Each floor in a house is approximately 2.6m, including the joists.

And the measurement is to the shower-head, which is about 2m above FFL (Finished Floor Level).

The HP installer will almost certainly fit a pressure-reducing valve on the cold incomer to the property.
Otherwise he has greater risk that the high water pressure will cause leaks in the new pipework he fits for domestic H & C feeds.

It won't affect the circulating water that goes through the heat-pump and radiators because that's a closed system.
It's pressurised to about 1½ Bar through the filling-loop when it's installed.