Converting gravity fed to unvented hot cylinder - cost?

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Hi,

Has anyone any idea of how much I should pay someone to convert my gravity fed hot cylinder to an unvented pressurised system?

The cold water tank is just above the cylinder inside the loft.

Is their any disadvantage to converting to unvented?
ie. possible weak pipe jpints leaking under high pressure water?
 
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You need to check your cold mains pressure and flow rate before considering this.

Ideally you will need in excess of 3Bar and 20 l/m flow.

You will also need 22mm cold mains to supply the unvented cylinder an any cold supplies to showers etc re-connected to the balanced side of the cold supply to the cylinder.

Can't really give an accurate idea of cost as there are so many variables, but a very rough guess could be £1500 -£2000 + VAT.
 
Thanks gas4you.

The mains pressure is pretty high, but how do I measure it?

... their is a 22mm cold supply already to the existing tank.
 
Thanks gas4you.

The mains pressure is pretty high, but how do I measure it?

... their is a 22mm cold supply already to the existing tank.

You need to buy a weir gauge to measure the flow rate and a wet pressure test gauge( monument or rothenburger) the gauge needs to be put as close to the mains incoming supply as possible, and you need to take about 5 different readings over the day. These have to be both standing and operating pressures. First thing in the morning and early evning are a definte must. more demand at this time.

And by your comment of 22mm already at the cylinder, i think your missing the point. your incoming main at your stop tap needs to be 22mm and go directly to your cylinder and no where else. all your cold water is balanced at the cylinder. It's not just a case of fit and away you go. iit's major plumbing over hall. Not to mention, informing the water board and buliding control of intention to fit.. Best bet, get a reliable and trustworthy plumber round for inspection.. Go on local water company or CIPHE website and find a registered approved plumber.. Good luck
 
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if you can stretch finances a bit more fit a solar cylinder (twin coil) about £450 more but you can add a panel at a later stage.
 
if you can stretch finances a bit more fit a solar cylinder (twin coil) about £450 more but you can add a panel at a later stage.

Thats exactly wot im doin at the mo, well i say the mo it's been like it 18 months :LOL:

Snaked the pipe work into both coils so am pre heating the cylinder through the solar coil so boiler aint on as long..
 
And by your comment of 22mm already at the cylinder, i think your missing the point. your incoming main at your stop tap needs to be 22mm and go directly to your cylinder and no where else. all your cold water is balanced at the cylinder. It's not just a case of fit and away you go. iit's major plumbing over hall. Not to mention, informing the water board and buliding control of intention to fit.. Best bet, get a reliable and trustworthy plumber round for inspection.. Go on local water company or CIPHE website and find a registered approved plumber.. Good luck

Thanks ... why must it be 22mm all the way from the mains?

My niave limited knowledge of pressure/volume ... if you use say 15mm pipe dopesnt the pressure increase? Boyles (or is it Charles?) law? PressurexVolume=constant

I used to have a combi system running off 15mm pipe that gave mains pressure throughout the house ... uhhmmm ...

Yeah .. I have considered solar ... hard heard good things, in summer never having to heat the water from any other source ..
 
Solar in a average 3 bed property will only save you between £80-£120 a year, not really worth it IMO, financially.

It's the main reason I came out of it.
 
I've no doubt there will be some reaction to the suggestion of an unvented thermal store - for some reason there seems to be a fairly strong prejudice against them on this forum. However, I fitted one at the end of last year and we are finding it absolutely brilliant.

We are a family of 4 and more often than not have 4 showers in the morning. Since fitted - about 5 months now - we have not run out of hot water. The boiler was updated to a condensing Worcester Bosch in December and it has made no difference to the performance. We have just installed a second shower to a loft conversion and both showers run at high pressure at the same time. The hot water supply is piping hot and has to be blended down at the tank for safety. I really am struggling to think of any drawback whatsoever.

The only thing I can think of is that we used to notice an initial temperature drop at the shower - in the first 15-20 seconds or so. This was because the shower was then a manual valve which needed to be adjusted to compensate. The shower has since been upgraded to a thermostatic and now the temp drop is not noticeable at all.

Only other thing I would say is that we have been extensively knocking the house around for a major loft conversion and rear extension. This gave me the opportunity to instal new 22mm pipe to the tank for both cold and hot water and I also took 22mm pipe right up to both showers. We also have excellent water pressure and flow - 5bar at the main. The tank is reduced down to 3bar so is running at max.

It sounds like you have good supply and pressure though so I would have thought you would get a similar result to me.
 
...My niave limited knowledge of pressure/volume ... if you use say 15mm pipe dopesnt the pressure increase? Boyles (or is it Charles?) law? PressurexVolume=constant..

That may be true for a compressible gas under static conditions, but water doesnt compress. In a dynamic flow situation you trade off pressure for flow rate (Bernoulli's principle) so the pressure decreases as the flow increases. That's what makes a Giffard injector work.

I used to have a combi system running off 15mm pipe that gave mains pressure throughout the house ... uhhmmm ...
A combi works with a 15mm supply because the limitation of the flow rate is the rate at which the boiler can heat water, which is usually well within the capacity of 15mm pipework, as many can only heat enough water to supply one tap at a time.

For stored hot water the limit on the delivery rate is the flow rate and dynamic pressure available from the mains water supply, so a larger size is selected to optimise that.
Using 15mm pipework would restrict the performance of the system to something like the performance you would get from a combi boiler.
 
You need to check your cold mains pressure and flow rate before considering this.

Ideally you will need in excess of 3Bar and 20 l/m flow.

You will also need 22mm cold mains to supply the unvented cylinder an any cold supplies to showers etc re-connected to the balanced side of the cold supply to the cylinder.

Can't really give an accurate idea of cost as there are so many variables, but a very rough guess could be £1500 -£2000 + VAT.

Hi,

Current Situation - I have a cold water storage tank in the loft i.e. gravity fed system. I also have a solar water tank in the storage room near kitchen which stores hot water in the tank through solar energy.

Issue - pressure in the showers is very low.
I also wanted to remove the cold water storage tank as it occupies a lot of space and I plan to extend it into a bedroom in future.

Hence plumber recommends me to go for megaflow unvented cylinder installation that will serve dual purpose of excellent hot water pressure and removal of cold storage tank.

Questions

1) Will megaflow cylinder nullify the water heating through solar / boiler? that is i asume megaflow to only act as storage and pressure generator.
2) How much would it roughly cost for labour + materials to install the megaflow? builder says £2000
 
Anything is possible if properly specified.

Dont expect any old plumber to know much about that.

If Dan above is near you then why not pay him to specify exactly what you need?

Getting advise from a basic plumber and free comments over the internet is certainly not the best way forward for you. Potentially you could spend a lot of money and end up with something of little use.

Tony
 

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