Change loft tank for unvented cylinder

goodwithsaving

I have just moved into a property which has a 4 year old boiler (brand is 'Ideal') which operates on a gravity fed tank system. I am not used to these as I have always had new combi boilers installed in the past, however this time around I am completely broke and so cannot do this yet. I really don't like the tank approach - I never know when I require hot water, nor how much, and for 1 person it seems quite inefficient. 

There is no shower and water in this part of the country is expensive. Bathing every day would also flare my eczema.
To resolve the poor water pressure and enable me to install a suitable shower, my plumber has suggested an unvented hot water cylinder. This is going to cost a minimum of £1000 to do (rough estimate at this stage) and means I need to delay other works I wished to do to the property.

Does anybody else have experience of removing the loft cold water tank and replacing it with an unvented cylinder, and if so did it make a big difference? Would it be worth me putting up with no shower and saving longer to replace with a combi?

Thank you

Bendy_House

Hi GWS.

The flow from a combi or an unvented cylinder will only be as good as your incoming cold mains supply, so I presume your plumber has tested this - flow and pressure?

Assuming it's fine, then - yes - an unvented cylinder will/should give you a cracking shower, as will a combi whenever you get around to fitting one - it seems to be your preferred choice?

I'd be surprised if he could install an un vented cylinder for just £1k, tho' - I'd have thought more than that, but hey, if it's a quote it's a quote.

Do bear in mind that all the fitting of an unvented cylinder will do is to boost your H&C supply to give you better showers and stuff; you'll still have to heat - and keep hot - a full tank if you are going to want hot water on demand (as you would with a combi).

It would, however, also be silly to throw out a 4-year old boiler just to replace it with a combi (total cost of this would likely be £2k+, and you'd be losing a perfectly good boiler as well). Very wasteful.

So, what I would do is fit a 'booster' shower which looks a bit like an electric shower - that size of unit on the wall - but it has a small pump built in to it. I've only fitted and used these once - many moons ago - but was very impressed by how cheap, simple and effective it was - tons better than an 'instant' electric shower.

That should tie you over until the boiler starts to give trouble or you reckon it's time to go 'combi'.

For the most minimum of water usage, an 'instant' electric shower is an option, but they are generally pretty awful things to use, especially in winter.

Section62

goodwithsaving said:

There is no shower and water in this part of the country is expensive. Bathing every day would also flare my eczema.
To resolve the poor water pressure and enable me to install a suitable shower, my plumber has suggested an unvented hot water cylinder.

Is the water pressure that bad that a decent mixer shower wouldn't work?  Bear in mind more powerful showers use more water and energy and are more expensive to run.

If you need more pressure without spending a lot of money, the most obvious option would be to have a shower and a pump to raise the pressure and flow to the level you prefer.

An unvented hot water cylinder will operate at only mains pressure and flow, unless that is pumped too - is your mains supply up to the job without pumping?


If you later switch to a combi a standard mixer shower will still work, only the pump becomes redundant (if you have them installed as separate items)

Switching to an unvented cylinder seems like a lot of work and expense if you are intent on changing to a combi as soon as you can afford it (and/or have to replace the existing boiler).


Really it is a case of working out what you want, finding out whether your mains supply is adequate, then looking at which short-term option results in the least waste of money on plumbing fittings that will/may become redundant when the boiler is changed.

goodwithsaving

Thank you both. 
I feel a bit cautious about spending on a big tank when I want a combi eventually too. The mains pressure is fine, but the shower really is that bad (it only has a tap connected one / tap water pressure in the bathroom isn't good.
I know it is wasteful to remove a relatively new boiler, but at the same time it is wasteful heating a tank of water that doesn't get used (it is just me). 
You've both given me food for thought.....!

nofoollikeold

1. Modern hot water cylinders are very well insulated, and lose heat very slowly.  You can always add additional insulation.
2. If not already done, get a programmer fitted which controls the water separately.  Set it to come on for only an hour or two each day.
3. Don't forget that when the water in the cylinder reaches the temperature set on the cylinder's thermostat, the boiler is turned off so no further heat is supplied until the temperature drops several degrees.
4. I agree with Section 62 that fitting a shower pump would be an excellent short term solution.

Section62

goodwithsaving said:

I feel a bit cautious about spending on a big tank when I want a combi eventually too. The mains pressure is fine, but the shower really is that bad (it only has a tap connected one / tap water pressure in the bathroom isn't good.

If the bathroom tap pressure is really that bad then a decent plumber would be talking to you about finding out what is wrong and fixing that, rather than immediately going for an unvented option.

Unless you have very little headroom in the loft there should be enough head to get a decent flow rate from the bathroom taps if you have 22mm pipe.  The right mixer shower should then give you at least an economical shower, if not a power shower.  With the option of adding a pump to get about the best showering experience it is possible to get.

goodwithsaving said:

I know it is wasteful to remove a relatively new boiler, but at the same time it is wasteful heating a tank of water that doesn't get used (it is just me). 

If there's a decent level of insulation on the how water cylinder then the heat isn't entirely wasted. It can take days for a full hot water cylinder to go cold - and as Bendy pointed out, an unvented cylinder still needs heating the same as a gravity fed one.

In terms of economics, the 'saving' from a combi boiler might not be what you think it is.  Each time you need water the boiler has to heat the equivalent volume of water you are running off to get hot water out of the tap - so you are wasting gas and water each time you use a tap, unless you are using hot water so frequently the pipes never go cold.  When you take hot water from a cylinder, the hot water drawn off is replaced by cold, which sits at the bottom of the cylinder waiting to be reheated when the boiler eventually runs.  Add together the cost of the water and gas you use each time you use a combi boiler, then compare that to the cost of heat-loss from the cylinder.  Heat which, in the Winter, will be contributing to warming the house up.

Also on the economics, you need to save a lot of energy to repay the capital cost (several £k) of a replacement boiler.  If you need a replacement boiler then that capital cost has to be incurred anyway.  If you think that a replacement boiler will save you money, then that capital cost is avoidable.

Environmentally, the energy embodied in your existing boiler and plumbing system will be largely wasted if you decide to scrap it only part-way through its potential life.  You need to save a lot of energy in your water heating needs just to offset that wasted by throwing away a perfectly good boiler.

The balance of which is worse (economically/environmentally) isn't as obvious as it might first appear.


Then there is also the issue that the Government intends to wean us off gas boilers.  You might be able to buy a new combi as a replacement boiler, but there is no guarantee you'll be able to buy an affordable replacement for that one when the time comes.  Most options for our future hot water needs will involve storage of some form... anyone who already has a storage system now needs to think really carefully before switching to a gas-fueled 'instant' alternative, because that isn't where the future lies.

Bendy_House

goodwithsaving said:

Thank you both. 
I feel a bit cautious about spending on a big tank when I want a combi eventually too. The mains pressure is fine, but the shower really is that bad (it only has a tap connected one / tap water pressure in the bathroom isn't good.
I know it is wasteful to remove a relatively new boiler, but at the same time it is wasteful heating a tank of water that doesn't get used (it is just me). 
You've both given me food for thought.....!

Your aim is to ultimately go 'combi'. That's because it heats only the water you actually use, which should lower the water usage, and the gas bill too.

The cost of a combi is currently unjustifiable, since your existing boiler is young, working fine, and does the job of heating a tank. So, it wouldn't make financial sense to swap the boiler.

That leaves a few options in order to get a decent shower - which is seemingly your washing method of choice?

1) Swap the vented for an unvented. That will give you (since you've confirmed the mains pressure is fine) a very decent shower, so is one solution. Neg1 - it'll cost £1k+ in order to get a good shower, and you'll still have a stored water system which you ultimately don't want. Neg2 - your existing shower is taken off the taps, so that would still be a bit rubbish (hard to control, non-thermostatic, connectors blow off the taps!, etc). You could fit a proper thermostatic shower on the wall above the tap, but this will cost you, ooh, £500? So, it'll work, but cost ~£1500.

2) Replace with a combi. Seemingly the best solution for you. Neg - it'll cost ~£2-2.5k

3) Keep the existing vented cylinder since it works, and then improve the shower method 1. This will likely involve installing a home-counties flange in the tank, and a shower pump. Neg - this will cost ~£450+. Neg2 - it will likely blow your shower tap connector off, so you may need to update this part.

4) Keep the existing vented cylinder since it works, and then improve the shower method 2. Mount a pumped shower on the wall above your bath, such as an Aqualisa Aquastream Thermostatic. Neg - this will cost £500+. 

5) Fit an electric shower. Neg - this will give the most pitiful shower of them all, but it does work. It'll cost - ooh - from £200 upwards to have one fitted. Neg2 - you'll still be heating the cylinder of hot water for the rest of your house, so insulate that tank as best as you can.

Since your intention is to seemingly try and keep going, using as little water and energy as possible until you finally swap to a combi, then the leccy shower (5) might well be the best option. This means you'll be keeping the existing vented cylinder for all other hot water uses - kitchen tap, etc. - so it'll still need topping up with heat. You can add more insulation to this to help keep the hot water in.

Grenage

Why wouldn't you just connect a shower pump to the hot and cold tanks?

It seems a bit mad to scrap a boiler that works; the payback would take a very long time.

Section62

Bendy_House said:

Since your intention is to seemingly try and keep going, using as little water and energy as possible until you finally swap to a combi, then the leccy shower (5) might well be the best option. This means you'll be keeping the existing vented cylinder for all other hot water uses - kitchen tap, etc. - so it'll still need topping up with heat. You can add more insulation to this to help keep the hot water in.

I'd like to better understand the logic of this.  How does using peak/single rate electric to heat water via an electric shower whilst keeping a tankfull of gas-heated toasty-hot water standing by - but unused - work out to use less energy overall?  And the difference in water consumption is?

grumbler

Section62 said:

goodwithsaving said:

I feel a bit cautious about spending on a big tank when I want a combi eventually too. The mains pressure is fine, but the shower really is that bad (it only has a tap connected one / tap water pressure in the bathroom isn't good.

Unless you have very little headroom in the loft there should be enough head to get a decent flow rate from the bathroom taps if you have 22mm pipe.  The right mixer shower should then give you at least an economical shower, if not a power shower.

Why are electric showers so common then in houses with gravity systems?

And did anybody suggested an electric shower to the OP? IMO, it's a good option, especially if the water is expensive.

Bendy_House

Absolutely, Gren. But shower pumps like these are noisy, thrummy, gushy and generally a bit sh***y

Imo.

And they'll fire up whenever you run any tap. Urgh, nasty hateful things...

But, yes, an obvious temporary solution.

Oh, and they'll also blow GWS's shower attachment off his bath taps...