Unlimited hot water with 4 bathrooms - is it possible?

[marshian]

Just now, Nickfromwales said:

You said when he 'has to go to ASHP', so I'm charging you with entrapment.

 

No entrapment there at all - Not Guilty is my plea

 

I don't think there will be 

 

1. A ban on sale of gas boilers

or

2. Gas will run out

 

But I do think cost benefits to convert from gas and oil to ASHP will be incentivised by methods other than a grant and price of the fuel is one

[Gus Potter]

On 29/09/2025 at 12:16, Indy said:

Patience is not my strong point

You need to work on that.

[Nickfromwales]

1 minute ago, marshian said:

 

No entrapment there at all - Not Guilty is my plea

 

I don't think there will be 

 

1. A ban on sale of gas boilers

or

2. Gas will run out

 

But I do think cost benefits to convert from gas and oil to ASHP will be incentivised by methods other than a grant and price of the fuel is one

What if the ASHP option cannot provide sufficient oomph, as per the OP's request, then do you steer back to gas regardless due to necessity?

 

Guilty as charged. Send him down.

[-rick-]

1 minute ago, Nickfromwales said:

What if the ASHP option cannot provide sufficient oomph, as per the OP's request, then do you steer back to gas regardless due to necessity?

 

There will always be a heatpump option (with other tradeoffs of course):

 

https://clade-es.com/products/commercial-heat-pumps/elm-heat-pump/

[marshian]

1 minute ago, Nickfromwales said:

What if the ASHP option cannot provide sufficient oomph, as per the OP's request, then do you steer back to gas regardless due to necessity?

 

Guilty as charged. Send him down.

 

Because at that point he will be missing (hopefully) two x 30 min shower times and rattling around in the house without the need for "unlimited" HW........

 

Plus lets not forget - not having a tank rules out any PV assist to water heating during summer months if that is later added.......

 

Combis are fine for small houses, apartments and flats - madness IMO in a house with 3 bathrooms and a requirement for multiple showers at the same time

[Gus Potter]

On 29/09/2025 at 12:16, Indy said:

Any suggestions?

400l cylinder as a family compromise (you can be the good guy), your kids will grow up and develop nasty and often lazy habits. Just stick in a normal system with a bit of extra spare HWC storage capacity. 

 

Stick a electric element in the bottom of the cylinder for boosting , not available to phone/ app control.. an old fashioned switch.. on/ off at Dads request. Take no prisoners!

[Nickfromwales]

1 minute ago, -rick- said:

 

There will always be a heatpump option (with other tradeoffs of course):

 

https://clade-es.com/products/commercial-heat-pumps/elm-heat-pump/

If you have 8' x 8' x 5' of space (plus surrounding areas clearances)......

 

/ 4 ELM DIMENSIONS // B C A Unit Elm 75/60kW LN Elm 75/60kW SN Elm 105/70kW LN Height ‘A’ (mm) 2400 Width ‘B’ (mm) 2354 Depth ‘C’ (mm) 1455 Operating Weight (kg) Shipping Weight (kg) 1850 

[Nickfromwales]

1 minute ago, Gus Potter said:

400l cylinder as a family compromise (you can be the good guy), your kids will grow up and develop nasty and often lazy habits. Just stick in a normal system with a bit of extra spare HWC storage capacity. 

 

Stick a electric element in the bottom of the cylinder for boosting , not available to phone/ app control.. an old fashioned switch.. on/ off at Dads request. Take no prisoners! 

You lied about your age...you're clearly in your late 70's lol.

[Nickfromwales]

8 minutes ago, marshian said:

Because at that point he will be missing (hopefully) two x 30 min shower times and rattling around in the house without the need for "unlimited" HW........

That's "then" and the OP wants "now" solutions?

 

8 minutes ago, marshian said:

Plus lets not forget - not having a tank rules out any PV assist to water heating during summer months if that is later added.......

Defo.

[Gus Potter]

No I'm 61 I shite you not, respect your advise and it seems I need to "get with the programme" more. Now you being from Wales, you  should be tighter than I am.. are you going soft?

[Nickfromwales]

Just now, Gus Potter said:

No I'm 61 I shite you not, respect your advise and it seems I need to "get with the programme" more. Now you being from Wales, you  should be tighter than I am.. are you going soft?

Probably....but still happy to stay up and argue the toss.

[marshian]

1 minute ago, Nickfromwales said:

That's "then" and the OP wants "now" solutions?

 

And he has a multitude of suggestions  He can pick the bones out of the thread

[-rick-]

10 minutes ago, Nickfromwales said:

If you have 8' x 8' x 5' of space (plus surrounding areas clearances)......

 

/ 4 ELM DIMENSIONS // B C A Unit Elm 75/60kW LN Elm 75/60kW SN Elm 105/70kW LN Height ‘A’ (mm) 2400 Width ‘B’ (mm) 2354 Depth ‘C’ (mm) 1455 Operating Weight (kg) Shipping Weight (kg) 1850 

 

TBC wasn't a proposed solution to this thread and you have chosen the biggest one. Just saying that heatpumps exist in pretty much whatever capacity you want. Also heatpumps like this (top venting) won't need clearance on all sides.

[Gus Potter]

On 30/09/2025 at 12:44, Indy said:

That may be but it's unlikely to change their behaviour any time soon  And to be fair, even though I threw them under the bus a bit, I'm the same and can take extended showers pretty regularly so the answer is clearly that we need a solution to meet our demand/behaviour. I realise it's not the most efficient way of doing things but happy to pay a (small) premium to make the system work for me rather than the other way around. 

Ok it seems like the OP above has a big old house and wants a bit of luxury / not too bothered about bills, probably clocked that to install efficient systems is going to be disruptive / expensive and so on. 

 

So Nick. Is there any merit in tandem but small system propane gas boilers. In the summer one of the two just ticks over to meet the hot water demand I look after an old house that has UFH and in the plant room there are tandem propane boilers that switch depending on demand.  It's out in the country so if one goes down there is a back up. 

 

@Indy does that float your boat? 

[Oz07]

Poor OP getting crucified here because he wants to stick with a gas boiler 🤣. It's like a swear word round here. Not everyone wants to write a thesis on thermodynamics just to get heat and hot water. These new boilers are all coming ready for when they mix the gas too. My prediction is majority of UK homes still using gas for heating by 2050. Tories have said they will scrap net zero legislation, not that they will get in. But the tide is turning on the eco zealotry. 

[JohnMo]

1 hour ago, Oz07 said:

Poor OP getting crucified here because he wants to stick with a gas boiler 🤣. It's like a swear word round here. Not everyone wants to write a thesis on thermodynamics just to get heat and hot water. These new boilers are all coming ready for when they mix the gas too. My prediction is majority of UK homes still using gas for heating by 2050. Tories have said they will scrap net zero legislation, not that they will get in. But the tide is turning on the eco zealotry. 

Take away any eco stuff for a moment. My story, installed gas boiler on new build. Suffered overheating in shoulder seasons and summer, realised the only cost effective way to cool was A2A or A2W via floor. Already had UFH, so A2W was the least disruptive. Saw a bargain ASHP come up on eBay and bought after a few calculations. Initially installed as ASHP to UFH and had hybrid DHW via boiler. Few iterations had a full hybrid system. After a heating season running hybrid, did the calculations, having gas was costing me more than a £100 a year compared to ASHP alone. Gas went this year. In real cost terms (now on Cosy tariff, with battery and PV) my heating/cooling and DHW will cost at least 50% less than gas heating and DHW did.

 

In summer DHW is either PV through ASHP or cheap rate. All heating is cheap rate, all cooling is PV powered.

 

That is why I said fossil fuels boilers should be banned on new builds. I should have included renewables should be mandatory also. More save people from themselves.

 

 

[John Carroll]

Surprised to hear that, here, oil fired boilers are banned from 2022 and gas fired boilers from 2025, in new builds.

[Nickfromwales]

11 hours ago, -rick- said:

 

TBC wasn't a proposed solution to this thread and you have chosen the biggest one. Just saying that heatpumps exist in pretty much whatever capacity you want. Also heatpumps like this (top venting) won't need clearance on all sides.

My point is, to get anywhere even close to the performance gas, a luxury we’ve become used to, and to have very high kw ratings on tap (without the need to wait for the energy to ramp up) then the options for heat pumps are non cost effective, impractical, and very much not on the table.

 

BTW, I didn’t pick the biggest one to be obtuse, I picked it because that’s the one that stands any chance of matching the performance of a high kw gas appliance. So basically you need a heat pump that’s exactly the size of a small garden shed!!

 

And you need maintenance / service / repair access as per MI’s.

 

Remembering that this thread is being replied to specifically to answer the OP, for which we need to get a result for that unique enquiry, hence generalising about HP’s isn’t of any real relevance here; plenty of ASHP / GSHP chat on here for every other situation.

 

How to get continuous DHW, not from a heat pump; unless you’ve a very big back garden, a spare bedroom for the UVC, and a massive budget. 

[Oz07]

2 hours ago, JohnMo said:

 

That is why I said fossil fuels boilers should be banned on new builds. I should have included renewables should be mandatory also. More save people from themselves.

 

 

But why would you have it banned because it didn't work for you when it sounds like it would suit OP perfectly?

[John Carroll]

I think @Indy has lost interest anyway.

[Indy]

I have not lost interest, but find it really hard to argue against a group for merely mentioning that I don't want to have an ASHP. 

 

I have been following all the comments in the thread and really like the suggestion of getting an oversized boiler - especially the Navien NCB700 which seems to be able to offer 22lpm for 3 simultaneous showers. This would potentially meet our demand - we're unlikely to have 3 bathrooms in use at the same time but it's very likely that 2 showers plus the kitchen tap are being simultaneously used and this fits the bill.

 

The only concern I would have here is the pressure when 2 showers are being used together, so will speak to my builder about putting in a small cylinder plus this combi boiler and see what he recommends. 

 

Our use case is more focussed on DHW rather than CH anyway. The property is a new build built to BR standards, triple glazed and UFH all around, so well insulated and  shouldn't need too much in terms of CH. 

[Mr Punter]

I think a big combi could work well.  The modulation on the Navien seems good too.  Would a cold water accumulator ease the pressure drop issues?

[John Carroll]

30 minutes ago, Indy said:

I have not lost interest, but find it really hard to argue against a group for merely mentioning that I don't want to have an ASHP. 

 

I have been following all the comments in the thread and really like the suggestion of getting an oversized boiler - especially the Navien NCB700 which seems to be able to offer 22lpm for 3 simultaneous showers. This would potentially meet our demand - we're unlikely to have 3 bathrooms in use at the same time but it's very likely that 2 showers plus the kitchen tap are being simultaneously used and this fits the bill.

 

The only concern I would have here is the pressure when 2 showers are being used together, so will speak to my builder about putting in a small cylinder plus this combi boiler and see what he recommends. 

 

Our use case is more focussed on DHW rather than CH anyway. The property is a new build built to BR standards, triple glazed and UFH all around, so well insulated and  shouldn't need too much in terms of CH. 

 

The 54kW Navien, will give a flowrate of just over 22LPM at @dT of 35C, in other words a showering temperature of 40C from a winter very cold mains  of 5C, or 42C from 7C, so will supply 2 showers at a flowrate of 11LPM, acceptable? or 7.3LPM if 3 showers in service. 

 

What is the existing make/model/output of your existing Combi?

 

[Indy]

2 minutes ago, John Carroll said:

 

The 54kW Navien, will give a flowrate of just over 22LPM at @dT of 35C, in other words a showering temperature of 40C from a winter very cold mains  of 5C, or 42C from 7C, so will supply 2 showers at a flowrate of 11LPM, acceptable? or 7.3LPM if 3 showers in service. 

 

What is the existing make/model/output of your existing Combi?

 

 

It's a complete new build - so there is nothing to replace. It's a new installation. In our current place - we have a Worcestor Bosch Greenstar 37CDi. Does a commendable job though the pressure is a bit lacking for my liking. 

[-rick-]

6 hours ago, Oz07 said:

Poor OP getting crucified here because he wants to stick with a gas boiler 🤣. 

 

I'm sorry if anything I said comes across as this. Sometimes threads on here move away from the actual question and onto the theoretical. In this case the question was a about gas boilers and the early answers were about that. Then, as is common (and generally good) on these forums, you asked how an ashp user would handle this and we diverged off into the theoretical.

 

For what it's worth I think @Indy is being completely rational to stay with gas given the current state of the heatpump market, ie, if you are not careful you can end up with an expensive and shit install. Given that the gas market is unlikely to stick around forever, I do think it wise to allow for a future change to heatpumps but in the near term, it's not wrong to stick with gas for a high demand house.

 

Staying on the original question, the one point that is worth considering is whether the question would be better phrased as 'Whats the best way to provide hot water for 4 people to have long showers without a wait for HW tank refill' rather than asking for unlimited water. The answer may be different to that question than unlimited water, at the very least it opens up more possibilities which can then be compared on a cost/ease of install/maintenance basis.

Edited October 3 by -rick-