To comply with the warrenty of a shower pump I have to replace my 25 gallon water tank in the loft with a 50 gallon. I've read lots of postings on this subject.
I've read somewhere that in a year or two new regs will require a dry loft for new builds. There is always a good reason regs are changed and therefore although I do not have a new build I do like to be compliant.
Therefore my question is what soultions are available to achieve a dry loft? I will not consider a combi bolier solution, mainly because there is no backup for hot water should it fail, and unless you have good reliable mains pressure power showers are out of the question. Ideally I'd like to store my cold water downstairs in the utility room, ofcourse this would not work with a standard tank as there would be no pressure for taps above the tank etc etc.
We have a thermal store, and we're very happy with it. It's a single cylinder, with a built in header tank. The water in the cylinder is heated directly by the boiler, and circulated through the radiators. Hot water is achieved by passing cold mains water through a heat exchanger coil housed within the cylinder (some systems use a plate exchanger, which is in some ways better).
The system is simple, and has many advantages over non-store setups. The main one is the large energy buffering capacity, which allows long, continuous boiler burns.
The overwhelming reason for regs to change is that there are vast departments of people who's job it is to create new regulations and still others who's job it is to enforce them. If they didn't keep changing the rules, they'd have nothing to do.
I'd put a tank in the roof, and achieve karmic compliance-bliss by fitting every bit of clobber going to make it comply with the water by-laws. You'll be able to delight in fitting little strainer to stop insects coming up the overflow *AND* spend time calculating the flow resistance of said strainer to make sure it doesn't impede any possible overflow.
Then you can worry about whether there's enough insulation around/over the tank (and did that lid clip on nicely?) and whether you've left a sufficient gap in the insulation underneath it - while still making sure it's properly supported.
If you're going to store cold water, which might be a good idea if your mains flow-rate is poor, then the best place to put it is where gravity can deliver it back to the rest of the house.
Really? News to me. I was talking to somebody at WRAS a couple of weeks ago on a similar subject and this didn't come up.
There is a trend anyway to fit combi boilers into some types of new build property simply to be able to de-skill the plumbing operation.
However, in a new property it is possible to easily provision an adequate mains water supply. This may not be so easy in an older property, so before rushing off to chase imaginary regulations, do check the mains water supply to make sure that it is adequate.
The only way to meet the backup requirement is through some form of storage - none of the mains fed hot water systems inherently do that.
In terms of mains fed hot water systems, apart from combi boilers you can have a pressurised hot water cylinder - stores the hot water and is heated via a coil similar to an open vented system - or a thermal store where the bulk water is heated directly or indirectly by the boiler and that is pumped through an efficient heat exchanger when required. Both of these get you over the rate of heating problem of low to mid range combi boilers in that they store the hot water or the energy to heat it.
However, they are only as good as the mains supply.
Having said that, there are on the market, pressurised water storage vessels. IIRC, these operate on a similar principle to the pressure vessels used in sealed CH systems- i.e. with a diaphragm with air or nitrogen on one side, water on the other. The application is for where the static pressure of the supply is OK but the flow rate poor, and there is a requirement for periodically large amounts of water. I believe that these can be fitted on a ground floor - I tried to find the manufacturer, but can't for the moment. ISTR them being quite expensive, however.
If they are going to enforce dry lofts they would need to first enforce our water companies to deliver water under some sort of pressure 24 hours/day. I'm okay but a friend's system drops to almost nothing at peak times so things like the shower becomes unusable.
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