Hot water pressure problem, and replacing electric showers for mixer

[electrogear]

Hi,

We're having a few problems with low hot water pressure and shortly I'll be renovating both bathrooms and hopefully swapping the electric showers for mixer showers. Here's a breakdown of the current installation:

• 4 Bedroom House - 2 Showers, 1 Bath, 6 sinks total.
• Open Vented Hot Water/Central Heating System with 114 Litre CWS tank in loft / 131 litre cylinder in airing cupboard.
• Upstairs Hot Water Pressure: 0.2 Bar (approx 2 metres head)
• Downstairs Hot Water Pressure: 0.4 Bar (approx 4 metres head)
• Mains Cold Water Pressure 3.5 Bar.
• Barrier pipe installation (Hep2O) 10mm/15mm/22mm.
• All cold water systems currently mains fed.
• Currently only 2 adults/1child sharing but I'd like to future proof for full occupancy!

Q1 I'm guessing the best solution would be to get a 3 Bar pump for the hot water to roughly match mains cold water pressure for kitchen mixer taps etc?

Q2 When I replace the electric showers for mixer showers I'm guessing I'll need to have a second cold water feed from the CWS tank in the loft and via the 3 Bar Pump (dual type)?

Q3 Will it be feasible to still run all of the taps in the house from the cold water mains whilst running the showers on a separate feed, and how much ripping out of pipework will be involved?

Q4 Will I need to increase the CWS tank / cylinder sizes?

Q5 Decent whole house pump and thermostatic mixer shower recommendations?

Q6 Do I need to consider pressure rating of anything before installing pumps, and is there anything I've overlooked?

Q7 Rough cost for the above, doing it myself vs getting someone in?

In terms of ability, I'm an instrument/electrical tech with pipe fitting background so it is something I'm fairly confident doing, once I have done all of the research etc.

Thanks in advance, and sorry for all of the questions. Even if you can answer one or two of them it would help me get started.

 

[flameport]

1 - That is a solution but not necessarily the best one. It is not necessary to match the hot & cold pressure for a kitchen tap, kitchen mixers do not mix the water in the tap body, but have 2 separate concentric outlets. For the kitchen sink, the real issue is whether the hot water flow rate is sufficient, not that it has high pressure.

2 - Yes, anything which mixes hot and cold together must be supplied from the same source such as a twin pump. Pumped hot and mains cold will not work properly in a mixer tap or shower.

3 - Yes, provided they are separate taps and not mixers (except the kitchen one)

4 - If you intend two or more bathrooms to be used at the same time or similar times, then yes.

5 - Stuart Turner Monsoon.

6 - Any pipework and taps will be able to cope with 3.5 bar pressure. You need to consider whether you actually want all of the hot water pumped, as this will result in pump noise when any tap is turned on, including at night.

7 - Unknown and impossible to guess without a lot more details.

 

[electrogear]

1 - That is a solution but not necessarily the best one. It is not necessary to match the hot & cold pressure for a kitchen tap, kitchen mixers do not mix the water in the tap body, but have 2 separate concentric outlets. For the kitchen sink, the real issue is whether the hot water flow rate is sufficient, not that it has high pressure. The kitchen mixer I have now requires 0.5 Bar pressure minimum and it does mix the water in the tap body but it's not thermostatic. As I have 0.4 Bar, it performs very poorly. The flow to the other downstairs taps isn't actually that bad. I think another problem I have is that the 10mm pipework to some of my taps is causing poor flow. I was hoping that increasing the pressure before the point where the pipework bore is reduced it would also increase the flow.

2 - Yes, anything which mixes hot and cold together must be supplied from the same source such as a twin pump. Pumped hot and mains cold will not work properly in a mixer tap or shower. Thanks for confirming

3 - Yes, provided they are separate taps and not mixers (except the kitchen one). I do have 3 other mixer taps, so I guess I'll need to give that some thought! None of them are thermostatic..

4 - If you intend two or more bathrooms to be used at the same time or similar times, then yes. Thanks, so I guess I need to work out what maximum usage would be at any one time.

5 - Stuart Turner Monsoon. Thanks

6 - Any pipework and taps will be able to cope with 3.5 bar pressure. You need to consider whether you actually want all of the hot water pumped, as this will result in pump noise when any tap is turned on, including at night. I can live with pump noise as long as it's not going to wake anyone up. I'll have to look into dB levels from different pumps then. I think waiting several minutes for hot water from a tap is more of a problem than noise in the night, so it's a fair trade-off!

7 - Unknown and impossible to guess without a lot more details. No worries, I'll figure it out

Thanks for your detailed response. My answers in red.

 

[Madrab]

Mains hot water is the easier and most reliable system for your setup IMO, if the mains flow is up to it. How many L/Min at the mains cold closest to the stopcock?

Was going to say, it depends on the kitchen mixer type, dual or single flow, you could have either. You said it's a single flow tho (mix in the body) so needs a balanced supply. 10mm can be used but it does need better pressure

Unvented hot water or thermal store if flow is suitable would be a way to go if it's along term solution. Unvented needs a qualified engineer to install tho, thermal doesn't.

whole house pumps are fine, short and medium term but you can run into a lot of issues further down the line when they start to wear out, therefore impacting the whole house. Well serviced unvented/thermal will last for years. Unvented/thermal also means both cold cistern and cylinder are removed replaced with a new high efficiency hot water cylinder and should hook straight into the existing hot water circuit, with minimal alterations. No change to the cold circuit apart from running mains to the cylinder.

 

[electrogear]

Mains hot water is the easier and most reliable system for your setup IMO, if the mains flow is up to it. How many L/Min at the mains cold closest to the stopcock? I get 12 - 15 L/Min at the mains cold but I daresay it's higher as I'm measuring at a mixer tap that restricts the flow quite a bit. When you say mains hot water do you mean via a Combi boiler? At the moment I have a normal condensing (heat only) boiler. If that's what you mean, I thought due to the through-put combis were only any good for small properties where there's not more than one shower/tap being used at a time?

Was going to say, it depends on the kitchen mixer type, dual or single flow, you could have either. You said it's a single flow tho (mix in the body) so needs a balanced supply. 10mm can be used but it does need better pressure

Unvented hot water or thermal store if flow is suitable would be a way to go if it's along term solution. Unvented needs a qualified engineer to install tho, thermal doesn't.

whole house pumps are fine, short and medium term but you can run into a lot of issues further down the line when they start to wear out, therefore impacting the whole house. Well serviced unvented/thermal will last for years. Unvented/thermal also means both cold cistern and cylinder are removed replaced with a new high efficiency hot water cylinder and should hook straight into the existing hot water circuit, with minimal alterations. No change to the cold circuit apart from running mains to the cylinder. Does a closed/pressurised cylinder have a larger volume then to compensate for losing the CWS tank? Also how much roughly are you looking at for such a system? If it's running into the thousands, I think I'd rather buy a £300 pump and replace it every few years as required. Then again, I do like the sound of getting rid of the CWS tank, but got to be rational here...

 

[electrogear]

I have just done some research on the thermal store too. If I understand it correctly, it's basically like the system I have now, but a second coil runs through the cylinder so that mains cold water can be passed through to provide mains pressure hot water which is then mixed through a thermostatic valve, so it is kinda like having 2 heat exchangers? I like that idea, and if I can do most of the installation work myself it will save me £££. Thanks for the heads up on that. Any more advice on pros/cons would be appreciated