System boiler or change to Combi - Bathroom refurb

Momanns

Hi all - In the process of getting some quotes for 2 bathroom refurbs (En suite & separate upstairs bathroom which back onto each other). 2 of the 3 quotes have recommended whilst this is being done, to change from the current setup of a system boiler (Cold tank in loft - hot tank in upstairs cupboard) to a combi boiler. I'm told that with the current setup we would need pumps for both showers and the boiler is likely pushing onto 10 years in age.

For context, it's a reasonably sized 4 bed with 2 adults & 2 kids so we don't use an awful lot of water between us. 

Its something I've thought about doing as I'm sure the combi would be more efficient/practical but I'm also concerned about being unnecessarily "upsold"!  Is it worth taking the hit for something that may save on bills and we would have to do in the future anyway?

macman

A combi will depend on adequate flow rate and gas supply (the latter may need upgrading). Have both these been checked? A combi is not suitable if both bathroom are being used simultaneously, as the combi can't supply sufficient flow.
A combi is in no way more 'efficient'. and won't save on bills: the only waste from a system boiler is heat loss from the hot tank, which is minimal and generally serves to warm the house in winter anyway.
A decent boiler. system or combi, should last ten years or more, and if it doesn't then there's no need to change it just because you are upgrading the bathrooms. It's also more expensive to go from system to combi than system to system, because of the extra plumbing and removal of the tanks.
If you are looking for power shower pressures (pumped0, you won't get them from a combi.

Momanns

Hi macman, thank you for the quick reply - Definitely looking for a decent shower and had thought the combi pressure would be better but guessing this isn't true?

Do you know if the additional pump for the shower would be all that's required to make a difference? We've been quoted £300-£400 for each pump (South East)

JohnSwift10

There are 2 of us in my house and if my wife is having a shower upstairs it takes ages to fill the basin downstairs to wash the dishes.

Eldi_Dos

Have you considered putting an electric shower in one of the bathrooms you are refurbishing incase boiler ever breaks down, certainly helped us when our boiler packed up during first lockdown.

Momanns

Hi Eldi_Dos - Haven't actually - will mention this to see what comes back from the guys doing the quotes!

Section62

Momanns said:

Hi Eldi_Dos - Haven't actually - will mention this to see what comes back from the guys doing the quotes!

If you are keeping the system boiler then it makes more sense to get an immersion heater fitted to the cylinder.  That way you have whole-house hot water in the event of boiler breakdown, and you don't have to pay the increased costs of electric showering when the heating system is running normally (just make sure the immersion heater is switched off when not needed).  Immersion heaters are typically cheaper to buy and last longer than electric showers.

fezster

There's a lot of variables to this question and simply fitting a combi is not always suitable. You need to know what your incoming mains flow rate is, for starters.

What are you looking to achieve with the showers? Do you want both to be powerful (in which case an electric will not cut it)? Do you need to use both at the same time (unlikely a combi will be able to do this unless it is a very large storage combi)?

You'd be better off speaking to someone who can give you a range of options and the pros and cons of each. If your boiler is otherwise fine, changing it is not going to save you money in any scenario. So the only reason to do so is if you require a combi to fulfil your needs.

Jeepers_Creepers

Momanns.

You have a number of options, each of which has pros and cons - it all comes down to what is essential for you, and what is desirable.

1) Keep your existing 'vented' system.

Pros: cost saving, obviously! And a system boiler is the least-stressed of boiler types, so your 10-year old jobbie should carry on for a good few years yet. With added pumps, you should have superb showers.

Cons: You'll most likely need shower pumps for your two new showers due to them being upstairs. I personally hate pumps due to their 'gushiness' and noise, tho' they can be insulated to a fair degree against this. There is also every chance that your pumps could be fitted in the loft - so totally out of the way - and placed on a thick insulating panel, and perhaps even inside bespoke insulated boxes. BUT, I doubt you'll be having showers after folk have gone to bed any more without annoying them. Any other cons? I can't think of any.

2) Fit a combi.

Pros: this will give you excellent showers, but only one at a time. (Ok, there are 'super' combis that might manage two, but I don't think I'd go there.) Space-saving - you'll free up the cupboard where the hot tank is, and lose the cold tank in the loft. Endless hot water with no limit. Full mains pressure and drinking water from all taps.

Cons: Initial cost of installation. Needs a good mains flow and pressure (I'd suggest min of 20lpm and 2.5bar). More moving parts, so more likely to go wrong over time.

3) Go 'unvented'. (Ie, a mains-pressurised hot cylinder, still heated by your system boiler.)

Pros: Can provide a superb hot water flow, often capable of supplying two showers at the same time (depending on how good the mains F&P is). You lose the cold tank in the loft. With an immersion heater fitted, you have a back-up system of hot water should the boiler go kaput.

Cons: Initial cost of installation. Extra annual servicing (needs a G3-certified cove to check it). Only as good as your mains supply (tho' there are ways of boosting this).

So if, for example, two gushing showers running at the same time is 'essential', then (3) is the obvious way to go. If freeing up cupboard space is a priority, then (2) gives you that. If lowest possible cost is important, then (1) is most likely your best bet.

Each is a compromise to some degree.

Momanns

Hi all - thank you for the responses. This is becoming more complicated than I realised! Will ask the companies I've contacted for the quotes and try and work out the best solution. Cheers!

Jeepers_Creepers

First question for the combi or unvented options is, 'what is my mains water pressure and flow rates'?