Anyone any experience with potable water storage tanks?
I'm looking to replace the old tank in the loft with a new one and I'm thinking that it would be nice to fit one that I'd be (more) happy to drink out of - and being able to use hot water at the tap to fill the kettle with, etc.
For more details of the plumbing: A twin impellor ST pump sucks water out of the tank, then one side goes to the cold taps in the bathroom, the other side through a thermal store for hot to the bathroom and kitchen - but cold in the kitchen is mains - high pressure, low flow, hence a tank in the loft.
I've found a few places online (e.g. first google hit was
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just wondering if anyone has any experience and (probably more importantly!) can you taste the plasticy stuff they make them out of? Loft gets a shade warm in the summer and very cold in winter!
All plastic cold water storage cisterns to the relevant British Standard have been potable quality for 25 years or more. They should have insulation, a snap-tight lid, a screened air vent, screened overflow, etc. This is the byelaw 30 kit you may see mentioned.
You can't taste the plastic. The water will degrade if it geys warm or if the lid isn't refitted after maintenance. The tank will have installation instructions. It should be installed on a marine ply base.
All our water(*) goes through the storeage tanks (3 x 100 gallon) in the loft. Historical reasons, mains water didn't arrive here until about 30 years ago.
When we moved in they weren't well covered or have fly traps etc on the overflow. There was a certain amount of detritus in the bottom of them, from building debris to dead insects and mouse. Cleaned all that out, within the first year or so. Wiped the insides down with a bit of dilute bleach, fitted close fitting lids Bye Law 30 stuff etc and lagged. We have never noticed any "taint" to the water of suffered any illness.
With modern mains water supplies and covered insect proof tanks I don't think there is any problem at all with stored water. If the water was from a well or spring I'd filter and UV treat it before storeage but you'd do that even if using direct.
(*) Until recently, some DHW is now direct from the mains via the thermal store. All cold and other DHW is still via the tanks
Assuming the water is treated mains water with trace chlorine in it, being kept too warm is going to be more problem than the length of time. Insulating the tank well so it doesn't heat up in the summer is probably very important - my loft gets up to 50C in the summer. You might want to think about fitting two lagging kits, and standing the tank on a sheet of celotex/kingspan (on top of rigid base), and possibly to top vents in the loft to reduce max temperature in summer (although they may increase chance of freezing pipework in winter).
Thanks for the replies - sounds like it's a bit of a no-brainer then. My biggest issue now is finding one that will fit through the hatch as it's rather small.
I also don't think water "turnaround" time will be overly long either - we can drain the current tank if we fill a bath, so a couple of showers every day will move a lot of water through it anyway. Will go up later today and measure it to work out what size new one to get.
It's also intersting to note what they used to use here - a large (huge - I reckon it's at least a meter cubed, so 1 tonne of water!) galvanised steel tank. They just left it there when some prior owners fitted the current plastic tank... It's now full of old loft insulation and presenting me with a bit of a problem as I'd really like to remove it - one day!
You can get collapsable ones for this purpose (although I never tried using one), and of course you can use more than one and link them together.
There were several in my brothers loft (the house had at some stage been split into flats with separate tanks, and then back into one house). When he switched to a combi, part of the work specified was to remove all the tanks. First problem was that several of them still had a reasonable amount of water in them, although not connected up for 10+ years. Having got that out, the plumber cut them up with an angle grinder, and I do not know how he managed not to burn down the house - apparently sparks were flying everywhere, including out of the loft hatch and bouncing down the stairs.
There is a small river at the bottom of our graden and I have toyed with the idea of using it then getting a water meter to save a bit of money but it would require some 100m of hosepipe to get it close to the house (garden is not that big, just detatched!) Getting a submersible pump to it isn't an issue, but getting electrickery to the pump is - even assuming I could get a hose there, so preferably, I'd need a pump at the house end that could suck air through 100m of pipe before it got wet... Total lift isn't much but needs to be considered...
I have great pressure from the mains (8bar), but a piddly low flow rate. There is a blockage/kink/crush in the buried pipe coming into the house which I don't currently have the resources to look for (ie. dig down through the tarmac/concrete/rubble to find) That's the only reason I keep the big tank in the loft...
In may particular case there is a baffle horizontally about 1/3 down form top ... creates a stratified layer - so I can stop HW at top mixing too easily with warm water below (reason will be explained)
In standard DHW set up the boiler loop just circulates the content of the boiler tails and the transfer could in the tank.
pretty inefficient .. as it can heat up quickly and cause cycling of your boiler .. loop is up to temp but HW tank isn't. You the store the water at temp .. that you will use .. and because you are storing water that has circulated around your boiler ... it's non potable. You also have (usually ) CH system run off the primaries as well .. each time rads call for heat boiler fires up.
In Thermal store the whole content of store are circulated around the boiler ... so when there is demand for HW .. there is a long efficinet burn, store heats up and holds HW.
Take off is indirect ... there are2 heat exchangers in the store ..
The lower one is where the heating loop is taken off .. in my case goers to underfloor heating manifolds ... one on each floor feeding 17 independently controlled zones. This is set via thermostat about 1/3 up the tank set to 60 deg; store (feeds pump & valve for boiler, and boiler demand signal) to keep heating water at 'warm' This is a closed loop of recirculated CH water.
The upper part of tank (above baffle) runs much hotter (as stat is at
1/3 point) and there is 2nd heat exchanger there ... Although complicated by pressure reg, strainers, drains etc. .... you can think of one side of this heat exchanger being connected to main cold water, what come out the other side is DHW ... it is through a 3 way thermostatic blending valve so you have a constant DHW temp. (set to 50 deg C in may case)
This DHW is at mains pressure on 22mm pipes ... so massive flow & pressure ... this means showers that could pressure wash you if you wanted :-)
In fact I have it set by regulator to 3.5bar and 25 Litres/min DHW at this flow & pressure is really good to have.
The large Thermal store means there is never any dropping off in temp when you are running a bath or using more than one shower at a time.
I have an extra fitted ... I run 22mm pipes DHW in a series circuit around every appliance, and at the very last one, run a 15mm return pipe to the Thermal store, where it returns via a very low speed circulator (multiple time settings pump) .. which makes water circulate around loop very slowly. This provides a pumped HW loop ...... so when I turn on a HW tap ... HW is instant, no need to run it to get hot ... same as they do in Hotels & offices. As soon as you open tap it is at 3.5 bar .. not dependant on pump, pump just circulates the 3.5 bar loop. This means no wasted water. (I also have underground rain water storage of 6500L .. so my water bill is very low)
I have heated towel rails on this loop ... so towels can still dry in the summer when heating is off .... the loop is fully insulated so no real heat loss.
One advantage is that the DHW is fully potable .. as is cold ... many people won't drink from upstairs taps as cold is fed from CW tank ... which may have dead pigeons in it as far as you know.
My CW and HW are both mains supply ... no storage at all.
The whole Thermal store is pressurised .. to 1 bar, as is CH loop.
Look at a mains pressure cold water accumulator. It stores cold water mains pressures. If you have a high flow combi they work together very well. It give high pressure and high flows. Higher flows than the mains can provide. It is the shape of a cylinder with an air charged pressure ball inside. Great for poor mains water pipe flows. No pumps needed and mains pressure on all taps.
Look at an accumulator. Perfect for high static pressure and low flows. Forget tanks and pumps. They are the last resort. Proper professional would not use tanks and pumps.
Do you have boiler? Oil? Gas? Hot water storage cylinder?
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