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Original poster

How do you manage to have a decent bath with a modern combi boiler

128 replies

theblackradiator · 26/11/2022 17:53

I have just replaced my 20 odd year old super reliable fantastic back boiler for one of these so called modern wonders (haha) combi boilers. I was advised to due to energy efficiency and running costs and I also struggled to find a gas safe engineer to service old boiler as younger guys now are not trained to service them. so I thought I'd go ahead and modernise and my god how I regret it! so much so I could cry it feels like a total downgrade compared to my old mid 90s backboiler. Running the bath takes a good 20 minutes or more longer, water no where near hot enough for a decent bath as boiler will only heat up to 65 degrees and by the time the bath is filled its going cold. we are a house that absolutely loves and needs baths to help with the aches and pains I suffer from. the central heating seems to work OK but to be honest I think old boiler kept the house consistently warmer and as for running costs I've noticed no difference at all as yet (according to my smart meter readings). no idea of the reason for my long post sorry, I just wanted to vent but if anyone does have any ideas of how to improve my bath water other than boiling the kettle! then any advice welcome. honestly feel I've just totally wasted £3000 to downgrade.

OP posts:
Lister80 · 01/01/2023 14:18

Snowflake2 · 01/01/2023 03:15

Whoever it is that has 55°C water temp, I thought it had to be 60°C min to avoid legionella?

OP it's insane that 65°C is the hottest your boiler goes. The engineer left mine in the wrong settings after servicing and it was 95°C. When the really cold spell hit recently my 60°C bath felt too cold within 15min of being in it without having added any cold water and I had to temporarily turn the boilers water temperature up a bit for a few weeks. I think the bath itself was cold and stealing the heat from the water, so you could try heating the bathroom before running the bath.

Those wanting constant hot water, there's a setting for that on my boiler, means it keeps a small amount of water hot and ready to use so no cold comes out the hot tap for handwashing etc. But means the boiler is on more than it would otherwise be so will presumably cost more.

If you want to top up the bath while you're in it it's easy, so long as you've got two feet and the right taps. Pull the plug at the same time as turning on the hot tap so the initial cold water goes straight out, putting the plug back in again when the water starts coming through hot. Use your feet to do it and you don't even have to sit up. If you're losing too much water hover the plug over the plughole to slow the flow rate. You'll need one foot on either end of the plug's chain to do that.

Not sure what combi boiler I've got but by the time I've gathered my pyjamas, chosen my clothes for tomorrow, used the toilet and found a book to read, the bath is ready. About 10min I'd guess? Then add cold water as appropriate and get in. I can also do the washing up and run a bath at the same time although the water pressure is crap when it's coming out of two taps at once. It's not a problem though, if it came out faster the bath might over run before I'd finished the washing up. I wash up under a running tap.

OP if your radiator is too cold have you turned up the thermostat on the radiator to the max? Mine goes up to 5, on 2 it won't feel particularly hot.

What boiler make, model and Kw do you have against number of radiators and hot water demand?
Thanks.

I am trying to ensure I don't fall into the pithole the OP has. I belive in buyer beware, i belive whilst a person providing a sevice has good intentions unless the customer does research and pushes on questions, answers, outcomes etc their expectations will fall short.

snowsilver · 01/01/2023 14:28

I resisted all persuasion to get a combi after my mother had a bad experience.
I got a new (oil) boiler and I still have my hot water tank with a back up immersion heater plus a back boiler to the multi fuel stove which gives tons of hot water when lit.

Snowflake2 · 01/01/2023 17:19

Lister80 · 01/01/2023 14:18

What boiler make, model and Kw do you have against number of radiators and hot water demand?
Thanks.

I am trying to ensure I don't fall into the pithole the OP has. I belive in buyer beware, i belive whilst a person providing a sevice has good intentions unless the customer does research and pushes on questions, answers, outcomes etc their expectations will fall short.

Show quote history

Sorry I don't really understand your questions (my bad). Here's a pic. 6 rads. Fitted 2018

How do you manage to have a decent bath with a modern combi boiler

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Original poster
theblackradiator · 01/01/2023 18:53

@Lister80 you must come back when you've decided and replaced your boiler and let us know how it is. I hope you have a better experience than me. I'm wondering if it would have been possible for me to keep my old hot water tank as it was also able to be heating by electric instead of gas but it's to late now I honestly never thought to ask if it could've been retained I could kick myself now for not doing some research. I just had the whole lot ripped out thinking a combi was they way to go and would be fantastic as everyone seems to have them these days. My only advice is definitely go for some kind of water storage tank if you have a bath. il probably end up spending thousands again at some point replacing mine for something with a water tank.

OP posts:
ermmm · 01/01/2023 19:02

Or boiler was set up to a higher temp so I was finding water too hot to wash with. Instead of using cold / mixer I just knocked temp down( well service guy was here he did it for us. Maybe adjust the temp on boiler to suit.

Moosey65 · 01/01/2023 19:50

Unfortunately the problem you're experiencing comes down to two issues.

The first is the output of the boiler, 24Kw is the smallest model made and will only generate about 10litres of hot water per minute when that water's temperature is raised by 35⁰C.
The second problem is that during winter the incoming cold water supply is around just 10⁰C.
This means that you only get 10 litres of hot water per minute at 45⁰C, if you want water hotter than that you will have to slow the flow rate at the taps which means you get even less water and therefore longer to fill the bath.

By comparison a 30Kw boiler gives about 25% more hot water.

Things will improve a little in the summer when the incoming cold supply is a good few degrees warmer and the boiler doesn't have to work as hard.

HackettGreen · 01/01/2023 20:51

This reply has been withdrawn

This has been withdrawn by MNHQ at the user's request.

Lister80 · 01/01/2023 23:10

Moosey65 · 01/01/2023 19:50

Unfortunately the problem you're experiencing comes down to two issues.

The first is the output of the boiler, 24Kw is the smallest model made and will only generate about 10litres of hot water per minute when that water's temperature is raised by 35⁰C.
The second problem is that during winter the incoming cold water supply is around just 10⁰C.
This means that you only get 10 litres of hot water per minute at 45⁰C, if you want water hotter than that you will have to slow the flow rate at the taps which means you get even less water and therefore longer to fill the bath.

By comparison a 30Kw boiler gives about 25% more hot water.

Things will improve a little in the summer when the incoming cold supply is a good few degrees warmer and the boiler doesn't have to work as hard.

So as well as Kw it is the flowrate.

Just looking at the Worcester Bosch Greenstar 4000 30kW
So within the title it says 30KW is this linked to the Hot Water (as it goes on to state Central heating output 24kW) ?

Hot water flow rate 35°c (litres per minute) 12.3
Hot water flow rate 40°c (litres per minute) = 10.8
Are these good flow rates (they obviously get lower the higher the temperature)?

What ball-park/average KW and flow-rate should we be looking for if we want a hot boiling bath that fills up at a decent time?

All my life I have been used to a standard sized bath been at least 70% full within 12 minutes.

Boiler model titles - are misleading "Greenstar 32CDi Compact" does that mean its 32kw as the spec does not advise of this! Then there is another model "Greenstar Style 35kW" which clearly stats the KW - very frustrating!

Moosey65 · 02/01/2023 10:18

@Lister80 It most definately is the flow rate but higher kW and higher flow rate go hand in hand. Other than boilers that hold a stored volume of hot water, the flow rate from say a 30kw boiler at any given temperature rise from almost any manufacturer will be very similar.

Manufacturers will sometimes advertise their boiler using the flow rate at a low temperature rise say 30/35⁰C which gives a higher flow rate and looks quite impressive. But as the OP has unfortunately found out is of no use when trying to run a hot bath.

Personally i never install anything less than a 30kW for this reason. For me the larger the better but you will most likely have to increase the size of the gas pipe from your meter to the boiler to 28mm.

The two examples you give both the two figures of 32 & 35 will be the output to the hot water. For most boilers the kW available to the heating side will be less than that available to the hot water but still suitable for most houses.

The best technical information on any given boiler is to be found in the installation manual around pages 3/4. This will give you a better guide to flow rates. Most installation manuals for any given boiler can be downloaded online.

loislovesstewie · 02/01/2023 12:33

I genuinely think that if your combi is not heating the water or getting your house warm then you must have a boiler that is too small to carry out the task. I have a new Ideal Logic , 3 storey house, 2 bathrooms, and we are warm enough and have water that is hot enough and flows quickly. The water is set to 60 and is definitely 60. And are you using the pre-heat function ?

Original poster
theblackradiator · 02/01/2023 19:11

@loislovesstewie mines an ideal logic boiler too the logic max c24 do you find it to be noisy at all?

OP posts:
Original poster
theblackradiator · 02/01/2023 19:13

@loislovesstewie and No I've not used the preheat function yet I'm worried about the cost of doing so.

OP posts:
knittingaddict · 02/01/2023 19:23

We've had a combi boiler in this house for 15 years. The water doesn't get cold. It does take a while to run as you can't put it at a full flow, but it only takes about 10 minutes and is very hot. I have a very full bath too and still no issues.

sanityisamyth · 02/01/2023 19:24

The only thing I miss about my old house was the combo boiler! As much scalding hot water as I wanted instantly!

Lister80 · 02/01/2023 21:31

Moosey65 · 02/01/2023 10:18

@Lister80 It most definately is the flow rate but higher kW and higher flow rate go hand in hand. Other than boilers that hold a stored volume of hot water, the flow rate from say a 30kw boiler at any given temperature rise from almost any manufacturer will be very similar.

Manufacturers will sometimes advertise their boiler using the flow rate at a low temperature rise say 30/35⁰C which gives a higher flow rate and looks quite impressive. But as the OP has unfortunately found out is of no use when trying to run a hot bath.

Personally i never install anything less than a 30kW for this reason. For me the larger the better but you will most likely have to increase the size of the gas pipe from your meter to the boiler to 28mm.

The two examples you give both the two figures of 32 & 35 will be the output to the hot water. For most boilers the kW available to the heating side will be less than that available to the hot water but still suitable for most houses.

The best technical information on any given boiler is to be found in the installation manual around pages 3/4. This will give you a better guide to flow rates. Most installation manuals for any given boiler can be downloaded online.

thank you, very helpful response.

Looking at the Worcester Bosch range, this one should meet my needs...
Greenstar CDi Compact 36kw 40 degrees 12.9l/min. I wonder what 50 degrees is!

If poor I could opt for this one...... Greenstar 8000 Style Combi 40kw, 40 degrees 14.3l/min

I have been looking at Baxi and they quote 35 degrees flow rate, very misleading!!

What other manufacturers are worth looking at?

thanks.

biscoffonasunday · 03/01/2023 09:59

We have a Vaillant combi boiler, and find it very good.

loislovesstewie · 03/01/2023 10:44

I don't find it noisy, I do use the preheat function as it means that I get the hot water that is in the mini tank before the boiler starts to heat the water coming through. I haven't found it to be more expensive, I think it's probably a swings and roundabouts choice, it takes longer to heat the water without preheat although it will fire up regularly. I did check meter readings with and without the preheat and really there was little difference.

MadamLeota · 03/01/2023 10:58

I’ve lived in three houses. The first had an ancient back boiler, the second had a more modern system boiler and this one a combi. It was replaced about two years ago for an ultra modern Worcester Greenstar.
it’s the best system I’ve known. Water is instantly hot throughout the house, baths are steaming hot and it’s incredibly energy efficient.

i don’t understand those of you saying plumbers are advising you to look after ancient boilers because they are so inefficient they will be costing a fortune in comparison to their modern counterparts.

Elphame · 03/01/2023 11:39

I don’t understand those of you saying plumbers are advising you to look after ancient boilers because they are so inefficient they will be costing a fortune in comparison to their modern counterparts.

Mine was a reluctant replace due to certain parts starting to fail which could no longer be replaced. It was originally installed in the 1970s and lasted nearly 50 years. The one consolation I thought would be that our bills would drop significantly. They didn't. We saved around £10 a month on a monthly ddm of £214 and this was prior to the price increases. We will never claw back the £5K it cost to replace and upgrade the system (it had to be moved as the original location for some reason or other didn't meet current standards)

We have a combi in the annex - it's a decent make but is forever going wrong and already we can't get some key parts for it. It won't last 10 years.

EilonwyWithRedGoldHair · 03/01/2023 15:23

rwalker · 27/11/2022 20:34

Absolutely nothing to do with water pressure
Or radiators
in very simple terms
combi boilers heat the instant hot water by passing it over the flame the slower the water passes over the flame the hotter the water don’t turn your tap full on
also this time of year the cold water coming into the house will be colder so boiler will have to work harder to heat it

we have the same boiler just run the tap slower

as someone pointed out boiler cost about £1000 to convert from cylinder system to combi is a lot of work u have not been ripped off at £3000

Ours was about that much, we had to have hot and cold water tanks removed, new flue put in etc. some pipe work changed, some radiators replaced etc. Two people over about 4 days in the end. Had two quotes in the same region.

It wasn't like our previous house where we had a combi replaced with a new combi and a small radiator removed, that was done in a day by one person, much less upheaval, much, much cheaper.

On the plus side, we are now using considerably less electricity as we now run the shower off the combi instead of an electric shower, it's a massive reduction on last December's electric usage, and while gas usage has, obviously, risen it's more than offset by the reduction in electric. Compared to Dec 2021, and using todays prices, we used £40 less energy and had the heating on more (smart thermostat set to 17.5 day, 12 overnight vs a timer for two hours a day).

EilonwyWithRedGoldHair · 03/01/2023 15:25

Oh and in the summer, at the prices then, I worked out the old boiler was costing £10 a month just on the pilot light.

sevenbyseven · 03/01/2023 15:30

We used to have a back boiler with a hot water tank, now we have a combi boiler. I love it. I'd never go back to one with a tank.

sunshineandsuddenshowers · 03/01/2023 15:40

I love our combi (the new one, anyway). We have a 4 bed 4 storey house, and it's absolutely fine. We are a bath household (all 5 of us bath every day, tho we do share some water!) We can't really run two baths at once (water temp is fine, but flow is annoyingly slow) but that's fine, someone waits no more than 5 mins. Endless hot water, as much as needed. Fine to wash up and bathe at the same time. I did try turning the hot water temp down earlier this winter tho, and have put it back up again - I like a proper hot bath (ie I tend to add hot once I've got in) and with a lower temp I could never get it hot enough. PILs have an old system which heats the water to an insane temp - we have to have half a bath of cold in to make it safe, and I always burn my hand checking the first night - seems so wasteful.

DiaryofWimpyMumm · 03/01/2023 16:23

I have the same problem with mine it's a safety feature to avoid scalding and there's something under the bath to stop the heating of water going above a certain temperature. It sucks I agree

Original poster
theblackradiator · 09/01/2023 18:34

@Lister80 have you made a decision on which boiler to go for? I hate my new one more each day I've got my water temperature set to the maximum setting on the boiler 65 degrees and I can hold my hands under it when it's running at full temperature. it's absolutely rubbish no chance of mopping floors etc with steaming hot water. I'm considering seeing if I can have another hot water cylinder installed when I can afford it as this is pathetic for hot water. I don't think there is any fault with it as it seems to be operating fine just not good enough for me. @DiaryofWimpyMumm yes mines absolutely rubbish which boiler do you have? I don't appear to have anything under my bath though to limit temperature.

OP posts: