Back boiler > New unvented cylinder

Drew210385

Hello,

Just after a bit of advice.

We moved into a house with a back boiler about 5 years ago, I realise they don't make them anymore but according to the engineers when we get the annual service/clean it's quite new and is pretty much the latest model before they stopped being manufactured. It works perfectly and has a fairly modern looking inoffensive fire front and surround and we have no intention of replacing it ...BUT our shower pressure is awful.

We looked into shower pumps briefly but discounted them due to the noise, and we don't want an electric shower.

We've had 4 plumbers round for advice and basically they all said the same thing which is to upgrade to a combi boiler with quotes from all of them in the region of £4.5k which we can't really afford right now and we're also only planning to be here for only another 3 or 4 years max. However one plumber said we could replace the old vented cylinder to a brand new unvented one which would solve the issue of the shower pressure and would be more like £2k which would be much more doable for us. I'd never heard of this option before but it sounds like it could be a good plan.

Has anyone done had this done before or can give any advice re pros and cons?

southcoastrgi

What's your mains pressure like ?

You really need 20 litres a min flow & 2 bar working pressure.
£2k sounds a tad expensive 

Jeepers_Creepers

It's the £4.5k for a combi that sounds expensive to me! I know it'd be a new install in a different location, but still the boiler itself is only a round £1k and the rest are pipes and fittings... Perhaps it's tricky pipe routing?

Anyhoo, Drew, 4 plumbers have recommended a combi so I presume they all carried out the basic checks on your incoming mains pressure a flow to see that it's good enough to supply a combi? As Southcoast says, even for a combi you'd ideally want 20lpm flow and 2 bar pressure at a min. A decent combi will supply heated water at around 12-15lpm, and you'd want some reserve to also supply some 'cold' at the same time to allow shower blending and not to be too affected by other taps being used at the same time (they will have some effect, but the shower thermostat will keep the actual shower temp in control).

So, if you DO have 20lpm and at least 2 bar pressure, then the unvented (pressurised) cylinder would - in your case - also be an ideal solution. (In 'your' case - ie you are happy with your back boiler, don't want to fork out too much cash, and are happy to heat a stored hot cylinder. If it wasn't for that, then a combi would/should be a good alternative. But £4.5K?!).

You will need a specialist installer for the unvented cylinder, one with the quals for this work. I don't think £2k is excessive for this - the cylinder itself must be close to £1k? - but I am not a plumber. The old hot cylinder is removed along with the large cold tank in your loft which supplies it under gravity - hence the poor flow and pressure. The new tank will be unvented - sealed - and under mains pressure - the cold mains goes in t'bottom and pushes the heated water out t'top at mains pressure - ergo cracking flow and pressure. It'll also be balanced at all outlets - your hots and colds will flow in a similar way.

Provided your mains is good enough, that's the solution I'd go for in your position. And it will be a cure.

Drew210385

Yeah the guy that quoted for the cylinder does cylinder replacements all the time - loads of photos and reviews on his FB page, he checked the mains water pressure from the outside tap - I can't remember what he said now but he said it's fine, not brilliant but not terrible either.

I was just hoping to find someone in a similar position that added an unvented cylinder to a back boiler, but I guess it's a bit niche.

Jeepers_Creepers

Nothing niche about it; the fact it's a back boiler is quite irrelevant. 

Whether it's a system (sealed) or conventional (vented) boiler (yours will likely be the latter), they do the same thing - heat hot water in a cylinder. All you'll be doing is swapping a vented cylinder for a pressurised one - ergo be running on 'mains' power instead of gravity 'head'. 

The only issue is whether your mains P and F are good enough. Your plumber reckons 'yes', and he's the experienced one. 

(There are solutions to poor mains flow too, but it's very unlikely you'll need to go there.)

Homer_home

Where do you get the idea that shower pumps are noisy , they are not 

Why not an electric shower either ?

Jeepers_Creepers

Yuck - shower pumps are just nasty :-)
Electric showers are nastier still :-)

Drew210385

Oh I always thought they were noisy, and the plumbers I've had round have confirmed they are too I believe. They would also need to be attached to the cylinder which is in a cupboard in our bedroom so not ideal at all if they are noisy. Can you provide any more information?

Jeepers_Creepers

Some shower pumps are quietish, but it all depends on where they are installed - if the cylinder is in a bedroom, then folk in that room will definitely hear them. 

I'm sure they are better these days, but my experience of them - in other people's houses (I'd never have one myself :-) ) - is of water flow trickling out as you slowly open a tap or shower followed by a 'whooooosh!'. And a thrummmm.

Where's the shower located - is this near the cylinder? Could the pumps be fitted in there instead? 

But, how much is a good booster pump - a few £undred? Then it needs fitting and an electrical supply. Oh, and a flange fitting in the top of your cylinder. I doubt you'll have change out of £500 for all this. 

It's an option, yes, but one you'd want. 

Drew210385

I think I'm going to go with the vented to unvented cylinder replacement option..

Jeepers_Creepers

It's what I would do, Drew. Every house I've been in with an unvented cylinder, the hot water flow has been impressive. 

It does ultimately rely on the mains supply, of course, but almost certainly it'll be a HUGE improvement over what you current have, and 'natural' - no pumps, moving parts or silly stuff being required. :-)