I am looking to get my present vented hot water cylinder (installed 1984) replaced and upgraded with a S/S unvented model. This will improve DHW pressures at monobloc taps and showers plus dispense with the huge tank in the loft. Presently getting plumber quotes as I know by law you need a "ticket" to install pressurised systems. Does anyone have any tips or pitfalls for this job? 10MY (Sept 09) TD4 HSE Auto in Stornoway Grey (Now Gone)

08 FL2 TD4 SE Manual in Rimini Red (Now Gone)

Never heard of that being done before.....until last Sunday! A friend had just had his system back flushed and then said the plumber had replaced his header tank with an expansion tank making it into a sealed system. He was impressed with it and said all his rads were hotter. Didn't mention water pressure though but if it's all sealed and working under mains pressure I suppose it would be better. I think he paid just under £400 and the plumber was a friend if a friend. Didn't seem that expensive to me. Considering it myself now. Let us know how you get on. Past: FL2 TD4 HSE Auto
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Present: Audi A3 S Line.

That was work on the CH system, Steve. Changing that to unvented. Mine is still a vented system. Not sure of the benefits of changing that to sealed.
Changing to an unvented cylinder can be independent of the CH system. It effectively gives you mains pressure to both hot & cold supplies rather than relying on the loft tank to supply a head. Apparently most "new builds" are done this way now. 10MY (Sept 09) TD4 HSE Auto in Stornoway Grey (Now Gone)

08 FL2 TD4 SE Manual in Rimini Red (Now Gone)

An un-vented hot water cylinder is ok but just another thing to go wrong.
Have you considered replacing the boiler instead and doing away with the cylinder altogether? I had ours replaced a couple of years ago with a modern condensing boiler, hot water is supplied from it at mains pressure on an instantaneous basis. We now have an unending supply of hot water at a really good pressure and as a bonus our gas bills are reduced by almost 50%.
One piece of advice, if you do go for the boiler, size it on the basis of hot water output not heating output so as to ensure you have adequate hot water. Doing it the other way round enevitably means hot water supply will be disappointing.
Also pick a good make of boiler Worcester-Bosch is imo the one to go for.

if your house is fully energy efficient so as to pass a green deal assessment, then look no further than a wood pellet boiler. let the rhi tarrif pay for it and much more, I think its paying approx 12 pence per kw for 7 years.

If your house wont pass a green deal then spend no money on anything else , get insulating

Im going to insulate my house with £20 notes  At work
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Good advice, nicedayforit. However we replaced the gas boiler a few years ago when Gordon Brown paid back £400 for the trouble. At the time a combi was considered but I knew of too many people who had disappointing HW supply issues as you describe plus reliability issues too. As a consequence we kept as near as possible to the original. We have a Glow worm Flexicom Hx condensing boiler on a vented system. Impressive little boiler that has improved the heating and reduced gas consumption a tad. If the decision were to be made now I may well have gone for the Combi idea as you suggest. Thank you.

I like your wood pellet boiler suggestion, CG, but as you see above I am really looking at the DHW only as the Glow worm is still quite new. However, we do have a "proper" chimney (presently with a Jetstream gas coal effect fire fitted, but only used occasionally). I am liking the idea of using the hearth for a wood burner of sorts although SWMBO does not like the possibility of soot issues etc so that is on hold at present.

Regarding energy efficiency - our house is timber framed with brick cladding and full double glazing etc. (Walls are well insulated so gas bills are really low) I just need to improve the loft insulation once the loft water tank is decommissioned. I even have the rolls of wool up there ready to lay out! We have also had 3kWp pv panels on the roof for 2 years already on the early FIT tariff.  10MY (Sept 09) TD4 HSE Auto in Stornoway Grey (Now Gone)

08 FL2 TD4 SE Manual in Rimini Red (Now Gone)

I got £400 as well.

slap a pellet boiler in the hearth it will heat your water and look nice, get yourself in for the tarrif it really is a no brainer.

every KW of heat I use heating poultry sheds costs me 4p in fuel the tarrif pays me 8.6, the boilers produce upto 490kwh. life of tariff is 20 years commercial , only 7 in domestic.

FFRR sort of money once Ive paid the bank off

my farmhouse is on the large side , my plumber reckoned I could be earning up to £6000 in tarrif per year for seven years, boiler would cost £11000. At work
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"I can't always believe facts I read on the web" - Charles Dickens

winner by default of the tractor vs caravan race

If you go down the unvented route,make sure all the saftey comtrolls are fitted and the temperature/pressure relief vavles are routed to a safe place (it may lift at 90 c )You will have better hot water pressure,by law the guy fitting it should have his unvented card with him at all times.Not wanting to scare you but if it not fitted correctly you will end up with a bomb in the house.And yes I do have my unvented ticket.

That certainly looks good CG, for your situation where an industrial operation is adjacent to a large house. I can see it makes real sense. Definitely FFRR territory!

A quick internet search however reveals that for purely domestic situations, the industry in UK looks to be still immature, with examples of poor design, poor training and high reliance on imported products bringing about high unreliability rates and high cost service contracts.

For my modest 3-bed detached house in a small village estate, a mains gas system offers excellent reliability and (presently) relatively low running costs. Additionally, my hearth (in the lounge) has no back boiler or adjacent plumbing, necessitating major work even before the high capital expense needed to install a biomass boiler, the output of which, at (say) 20 kW would make the room uncomfortably hot. My solar pv system was a "no brainer" but looking at the RHI deal for even a solar wet panel system does not seem to be worth it to be honest.

Thanks for the input!

Archie, thank you, I was aware of the need for a professional installation. On my 2 surveys so far, the first thing shown to me was the unvented card on both occasions. And yes, the vent relief pipe routing has been the major item of discussion each time. Am learning a lot!  10MY (Sept 09) TD4 HSE Auto in Stornoway Grey (Now Gone)

08 FL2 TD4 SE Manual in Rimini Red (Now Gone)

We had our system updated this time last year. The cylinder was replaced, the two tanks in the loft removed, and pressure vessels added in the airing cupboard.

Mains hot water pressure and associated flow is amazing for showers. We replaced our two pumped showers with just mixer types.

Well worth doing...have not had any issues.

It is important that the system is installed by or checked by a competent person in accordance with building regulations due to the pressure vessels.

We had to have an upgraded mains cold feed up to the tank to ensure flow was good for the HW side. You will also need an relief pipe to run from cylinder to outside drain grille etc.

One of these http://www.telford-group.com/view/tempest-stainless/1391

Thanks for that, Richard. I have now had 3 plumbers come to survey. All confirmed they were qualified for unvented systems and I saw their cards. Our cold feed, although only 15mm, gives 4 bar pressure which they consider will be ok as the systems reduce pressure to 3 bar anyway. They all spent the most time checking the routing for the discharge pipe. 10MY (Sept 09) TD4 HSE Auto in Stornoway Grey (Now Gone)

08 FL2 TD4 SE Manual in Rimini Red (Now Gone)

Hi yes pressure will be ok through a 15mm pipe..but if you want flow then I'd recommend upgrading the feed to the cylinder to 22mm. Remember pressure is the same in a pipe how ever long it is or how wide it is...but flow is dependent on the resistance of the pipe (ie bore size)

So easy with plastic pipe to run new ones in. Unfortunately the discharge pipe has to be copper.

Point taken. I will raise it with them after I get the quotes.... 10MY (Sept 09) TD4 HSE Auto in Stornoway Grey (Now Gone)

08 FL2 TD4 SE Manual in Rimini Red (Now Gone)

Are you having your central heating switched to pressurised too? That removes another tank from the loft!