Unvented hotwater cylinder

[Tockalex]

To address pressure issues I've been advised to install an unvented hotwater cylinder in place of my existing combined cylinder and F&E tank.

If I do can I drain and refill this myself to carry out plumbing in the future or, like annual maintenance, is it a specialist job?

Thanks

 

[Softus]

The installation and the maintenance are both specialist jobs for which the correct training is a legal requirement.

 

[Tockalex]

Thanks, I am aware of that.

What concerns me is whether changing the washer on my kitchen tap also suddenly becomes a 'specialist' job instead of basic DIY.

As well as the kitchen tap, one of the toilet needs some attention and when money permits I have plans for the bathroom and kitchen etc etc - I have previously installed a bathroom where the hotwater system was a traditional gravity system - so know I can deal with that but given that installation and maintenance is a specialist role for an unvented system does that mean I wouldn't be able to do basic plumbing without a specially trained professional.

I don't want to go ahead and install the unvented cylinder if that is the case - presumably I could install a pump on the existing system instead?

Thanks

 

[doitall]

You can turn the water off to do work, although its best to have local isolating valves.

It's unlikely you would have enough storage water for a pump with a combination cylinder.

Remember an unvented cylinder needs a good mains pressure/flow

 

[Softus]

Thanks, I am aware of that.

In that case I don't (yet) know why you gave the impression of not knowing.

What concerns me is whether changing the washer on my kitchen tap also suddenly becomes a 'specialist' job instead of basic DIY.

As per doitall's reply.

As well as the kitchen tap, one of the toilet needs some attention

Unless you feed your WC cistern with hot water, an unvented hot water storage vessel won't cause you a problem with the WC.

and when money permits I have plans for the bathroom and kitchen etc etc - I have previously installed a bathroom where the hotwater system was a traditional gravity system - so know I can deal with that but given that installation and maintenance is a specialist role for an unvented system does that mean I wouldn't be able to do basic plumbing without a specially trained professional.

Maintenance of the appliance is quite separate to turning off the mains supply that feeds the secondary side.

I don't want to go ahead and install the unvented cylinder if that is the case - presumably I could install a pump on the existing system instead?

Think about it - if you had a flood that needed the mains cold feed to be shut off, it wouldn't make sense to have to call a specialist to avoid any danger.

 

[Tockalex]

Thanks - I genuinely mean it - it wasn't sarcastic! So apologies if I gave that impression. Thanks for taking time to answer lots of extra points.

Maintenance of the appliance is quite separate to turning off the mains supply that feeds the secondary side.

But surely the specific annual maintenance on an unvented cylinder is also on the 'secondary' side - I imagined it was checking the pressure vessel and relief valves etc- am I wrong?

Think about it - if you had a flood that needed the mains cold feed to be shut off, it wouldn't make sense to have to call a specialist to avoid any danger.

Yeah ok that makes sense - but it still doesn't confirm that I can refill it without the specialist.

I want to be able to have a shower but the shower head would be above the level of the existing tank, in the future I would also like to be able to put a shower room on the floor above (loft is above that)

My original solution was to put a cold water tank in the loft and replace the hotwater cylinder with a traditional one - more pipes but more familiar to me. However, the loft hatch is very small and I think (not sure) I have a trussed roof so increasing the size of the loft hatch seemed complicated and potentially structurally dangerous.

I was recommended the unvented cylinder by a salesman who implied it could probably cook me dinner whilst singing and dancing with no drawbacks at all!! - I’m trying to find out the other side of the story to make an educated choice - now - rather than once I'm committed.

So thanks for any comments on unvented cylinders and I would be grateful for any alternative suggestions on how to get the pressure I want.

 

[doitall]

Before you decide on anything you need to check the mains pressure and flow

 

[Tockalex]

That has been checked - with a pressure metre on the kitchen tap and with 3 taps running together and is adequate.

Sounds like you think it's a good idea if the pressure and flow is available?

 

[doitall]

Never fit anything else, but I would expect 2.5 bar and 25 ltr/m minimum from the mains.

The hype about servicing is just that Hype, you have a couple of safety relief valves, which no sensible plumber will touch because they always leak afterwards, some expansion vessels are internal, and you'll know if they need attention, some have anodes which should be checked depending on the water hardness, and a filter on the combination valve, which I haven't seen a blocked one ever.

Most guys can give it the once over when you have the annual boiler service, for a few extra quid.

I should add they are not a DIY install and the need to get it right is paramount.

 

[Onetap]

The hype about servicing is just that Hype, you have a couple of safety relief valves, which no sensible plumber will touch because they always leak afterwards,

You need to open the PRVs fully during a service to ensure that they operate. They regularly get concreted shut by limescale deposits.

 

[OvertonPlumber]

to legally fit unvented you should have a Unvented hot water ticket bpec or equilvalent.
Its worth noting that if you fit unvented without a ticket your public liability automatically becomes invalid. Working on UHW systems like changing taps is easy because all you have to do is close of the full flow lever valve to the combination valve then open a tap or open a discharge valve to relief the pressure and the water will stop dead.
These comments about servicing hype. Hmm if the tp valves are properly commisioned they wont build up limescale and wont leak. I have a 10 yr old megaflo and the discharge valves work fine.
We had a case of a 3yr old new build safety valve failed and combination valve failed on ariston 450ltr clylinder with a 28mm main going to it. end result was that an overpressuration on the main caused the polypipe elbow to rupture. polypipe blamed ariston. The client tried to claim of our public liability they failed miserably as they had not had the much hyped servicing on the cylinder.

 

[Onetap]

These comments about servicing hype. Hmm if the tp valves are properly commisioned they wont build up limescale and wont leak. I have a 10 yr old megaflo and the discharge valves work fine.

As someone else has commented, if the valves open/ are opened, they will often fail to reseat because they get limescale particles under the seat.

What sometimes happens is that the expansion vessel air charge is depleted or lost. When the water expands, the presure will exceed the valve opening pressure and it will pass the excess few litres to waste. If the valve then fails to reseat, there will be a continuous leak to drain. Because the valves are hot, the water evaporates and the dissolved limescale accumulates on the discharge side of the PRV. This can build up to the point that the valve fails to open when it is needed.

Operating the PRVs at full-bore is a requirement of the service. They soemtimes start leaking after that, but then you replace them. That's just the nature of the beast. They're cheap.

 

[Tockalex]

Thanks to eveyone who responded.

I do have very hard water so I guess it could cause the odd problem but it does sound like solong as I do get someone to do the regular mainentance there is no problem doing the basic plumbing myself.

THANKS

 

[Softus]

I do have very hard water so I guess it could cause the odd problem but it does sound like solong as I do get someone to do the regular mainentance there is no problem doing the basic plumbing myself.

I find this statement ambiguous.

If by "basic plumbing" you mean that you intend to install an unvented appliance yourself, then you will be acting illegally on two counts: (1) lack of notification; (2) lack of the relevant certificate of competence.

 

[Tockalex]

You seem to be very good at interpreting things the wrong way!

I personally wouldn't call that kind of installation basic plumbing - it may well be straightforward but that is NOT the same thing! - WHY would I want to install a potential hotwater bomb into my own home? However if I did probably the only point at which any one would realise and I could be prosecuted for having done so would be when I was scalded and homeless! Since you keep going on about it why have you not mentioned that is a requirement to ensure you local council is aware of the installation and that it requires building approval as well?

Surely the very question I asked indicated I was quite cautious -

can I drain and refill the cylinder myself?

As I said in response to your first post I am aware that it is a specialist installation and thought that it would have been possible to 'interpret' I was aware of this since I stated I was aware that maintenanance was 'specialist' in my initial query. All I wanted to know was if I could drain the unvented cylinder once installed to do various plumbing works. I have never suggested I install it myself - you keep trying to but not me! - how about a short helpful response to the question asked - rather than lots of abiguous interpretation and no definite response to "can I refill it myself"!