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Insulating cold water tank in the loft

Does what it says on the tin
MyNameIsUrl
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Insulating cold water tank in the loft

#177242

Postby MyNameIsUrl » October 30th, 2018, 8:27 pm

When tanks used to be mounted on the joists, the advice was to insulate up the sides of the tank but not underneath it.

My tank is on a platform about 3 feet above the joists – should I insulate both on the underside of the tank platform and on top of the ceiling directly below it? Or perhaps box in the sides of the platform, leave the bit of ceiling below it uninsulated, and allow a bit of heat to escape through the ceiling into an enclosed insulated box? Does the latter sound like overkill?

jackdaww
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Re: Insulating cold water tank in the loft

#177257

Postby jackdaww » October 30th, 2018, 10:12 pm

thinking i would not be able to clamber around in lofts the rest of my life, ( to replace ball valves etc ) i moved the tank down into the bedroom airing cupboard (holding the immersion heater) below.

another solution is a combi boiler - no tanks.

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Re: Insulating cold water tank in the loft

#177288

Postby AF62 » October 31st, 2018, 7:53 am

MyNameIsUrl wrote:My tank is on a platform about 3 feet above the joists – should I insulate both on the underside of the tank platform and on top of the ceiling directly below it? Or perhaps box in the sides of the platform, leave the bit of ceiling below it uninsulated, and allow a bit of heat to escape through the ceiling into an enclosed insulated box? Does the latter sound like overkill?


I would have thought it depended on a number of factors, such as location and occupation of the house.

The water in the tank is more likely to freeze if the house is somewhere where you are going to get prolonged periods of very cold weather and there is not a regular flow of water through it.

So if you live in the north of Scotland and take month long holidays in January, then taking extra steps to make sure it doesn't freeze is a good idea, but if you live in the south of England and the house is only unoccupied for a day or two in the winter, I would have thought a more simple solution is probably enough.

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Re: Insulating cold water tank in the loft

#177300

Postby bungeejumper » October 31st, 2018, 8:50 am

Moving the tank downstairs sounds like a lot of work! I'd be inclined to blow £16 on one of these:

https://www.amazon.co.uk/Dimplex-Ecot1f ... B00NT0X8K2

(Plus suitable insulation around). Might use a max of 1 kwh a day (thermostatically controlled), but it wouldn't break the bank during just the winter months.

BJ

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Re: Insulating cold water tank in the loft

#177307

Postby jackdaww » October 31st, 2018, 9:25 am

bungeejumper wrote:Moving the tank downstairs sounds like a lot of work!

BJ



==========================

yes -- i found it a lot of work!

but i was able to do it then , and couldnt now.

so theloft is empty of all gubbins and i dont need to pay anyone to get up there to replace ball valves and the like.

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Re: Insulating cold water tank in the loft

#177315

Postby MyNameIsUrl » October 31st, 2018, 10:16 am

AF62 wrote:I would have thought it depended on a number of factors, such as location and occupation of the house.

The water in the tank is more likely to freeze if the house is somewhere where you are going to get prolonged periods of very cold weather and there is not a regular flow of water through it.

So if you live in the north of Scotland and take month long holidays in January, then taking extra steps to make sure it doesn't freeze is a good idea, but if you live in the south of England and the house is only unoccupied for a day or two in the winter, I would have thought a more simple solution is probably enough.

A combination of the two, actually, but you've made me think about this a bit more, and the risk probably isn't the water tank freezing, but the pipework around it.

Without a frequent flow, the pipes could freeze in a small number of days. I maybe shouldn't insulate the pipes separately from the tank, but wrap insulation over the whole assembly to use the thermal mass of the water tank to slow down the cooling of the pipes.

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Re: Insulating cold water tank in the loft

#177575

Postby stewamax » November 1st, 2018, 11:23 am

I have done exactly as OP suggests: the cold water tanks (two, side by side, plus a third one in a distant part of the house) and the CH header tank are each on stilts. I have wrapped a cocoon of aluminium Thermowrap-type padded insulation over and around each tank right down to the floor, but left the underside open to the joists. Since the cold water tanks are immediately above the respective hot water cylinders in the rooms below, I rely on heat rising through the ceiling to keep the tanks from freezing. And since the CH header tank has an open vent (from the CH pipework) over it and directed down to catch any pump-over, this too serves as a useful freezing preventative.

Moving the water tanks down to a cupboard in a room would be a no-no as I would lose the 'head' and hot taps would trickle. (Cold taps are, of course, fed direct from the mains because the water needs to be potable).

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Re: Insulating cold water tank in the loft

#177587

Postby jackdaww » November 1st, 2018, 11:59 am

stewamax wrote:
Moving the water tanks down to a cupboard in a room would be a no-no as I would lose the 'head' and hot taps would trickle. (Cold taps are, of course, fed direct from the mains because the water needs to be potable).


===========================

yes you do lose head to the upper rooms, but its adequate in our bathroom except the shower which wasnt too good anyway so installed a triton pump - quite easy.

our cold taps do come from a tank , this allows nice even pressure at the taps.

the tank needs to be potable quality material - most are .

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Re: Insulating cold water tank in the loft

#177891

Postby jaizan » November 2nd, 2018, 8:46 pm

bungeejumper wrote:Moving the tank downstairs sounds like a lot of work! I'd be inclined to blow £16 on one of these:
https://www.amazon.co.uk/Dimplex-Ecot1f ... B00NT0X8K2
(Plus suitable insulation around). Might use a max of 1 kwh a day (thermostatically controlled), but it wouldn't break the bank during just the winter months.
BJ


Thanks !

Another option could be to put an aquarium heater in your tank and wire a thermostat in line so it only comes on when freezing.

Incidentally, if your tank is properly lagged, a large volume of water in the tank should freeze much more slowly than the small volume in the pipes going to the tank. So, of course, the pipes need the best quality insulation there is. I have the thickest pipe insulation, plus several layers of bubblewrap around the outside.

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Re: Insulating cold water tank in the loft

#177919

Postby pochisoldi » November 3rd, 2018, 8:54 am

jaizan wrote:
bungeejumper wrote:Moving the tank downstairs sounds like a lot of work! I'd be inclined to blow £16 on one of these:
https://www.amazon.co.uk/Dimplex-Ecot1f ... B00NT0X8K2
(Plus suitable insulation around). Might use a max of 1 kwh a day (thermostatically controlled), but it wouldn't break the bank during just the winter months.
BJ


Thanks !

Another option could be to put an aquarium heater in your tank and wire a thermostat in line so it only comes on when freezing.


Not a good solution.

1) Find me a water regs compliant aquarium heater (hint - B&Q have them on the same shelf as the pixie dust, tartan paint, sky hooks and rocking horse droppings)
2) If the control mechanism fails and the heater stays on, cycling on the heater's built in thermostat, you end up with a body of water getting warmed up beyond the 20deg C "too cold for legionella" zone, but not warm enough to enter the "too warm for legionella" zone. (There's a reason why my HW tank is set to 60deg C, and only gets mixed down to whatever temperature I need at the tap)

PochiSoldi

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Re: Insulating cold water tank in the loft

#177934

Postby jfgw » November 3rd, 2018, 11:16 am

Has anyone here heard of a tank freezing in an occupied property? (Or even in an unoccupied one?) If suitable aquarium-style heaters were necessary, they would be readily available. Just make sure your pipes are adequately insulated as these can freeze.

If you think that there is an unusually high risk of freezing, you could do your second suggestion and box in the sides of the platform. You could use Celotex or something similar.

pochisoldi wrote:2) If the control mechanism fails and the heater stays on, cycling on the heater's built in thermostat, you end up with a body of water getting warmed up beyond the 20deg C "too cold for legionella" zone, but not warm enough to enter the "too warm for legionella" zone. (There's a reason why my HW tank is set to 60deg C, and only gets mixed down to whatever temperature I need at the tap)


This is an important point. Note that the insulation is not just to prevent freezing in winter, it is to stop the water from getting too hot in summer. 20°C is the recommended maximum and 25°C is the limit to comply with the regs.

Julian F. G. W.

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Re: Insulating cold water tank in the loft

#178717

Postby jaizan » November 7th, 2018, 10:19 am

pochisoldi wrote:If the control mechanism fails and the heater stays on


This needs 2 failures -the thermostat on my heater needs to fail AND the in line central heating thermostat needs to fail.
Also, it needs to fail when no one is in the house, so the body of water has time to build up and maintain temperature.

The probability of all this happening is quite low, however of course people should be aware of that. Even if the odds on failure are about on par with those for winning the lottery.

It would also have been interesting to log the temperature during the summer heatwave, just to see what the temperature remained at over that period.

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Re: Insulating cold water tank in the loft

#178959

Postby stewamax » November 8th, 2018, 11:02 am

It would also have been interesting to log the temperature during the summer heatwave, just to see what the temperature remained at over that period.

Indeed. As anyone who has to do some manual work in a loft (insulation, electrics,...) knows, the worst time to pick is summer, especially if you need to wear a mask to avoid inhaling insulation fibres. And winter has the advantage that any wasps' nests there are empty ...

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Re: Insulating cold water tank in the loft

#178977

Postby pochisoldi » November 8th, 2018, 12:36 pm

jaizan wrote:
pochisoldi wrote:If the control mechanism fails and the heater stays on


This needs 2 failures -the thermostat on my heater needs to fail AND the in line central heating thermostat needs to fail.
Also, it needs to fail when no one is in the house, so the body of water has time to build up and maintain temperature.

The probability of all this happening is quite low, however of course people should be aware of that. Even if the odds on failure are about on par with those for winning the lottery.

It would also have been interesting to log the temperature during the summer heatwave, just to see what the temperature remained at over that period.


The proposed solution was a thermostat (effectively a frost stat, not a CH thermostat) feeding an aquarium heater.
The functioning of the thermostat built into the aquarium heater is not relevant here - if you try to set it to 5 deg C it probably won't work at all.
(it's unlikely that the thermostat will control down to that level), and it's most likely to be set at a level which will take you into the legionella zone if left long enough.

IMHO it's an under-engineered solution with a single point of failure as far a legionella is concerned.

PochiSoldi

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Re: Insulating cold water tank in the loft

#178994

Postby scrumpyjack » November 8th, 2018, 1:43 pm

We got rid of the loft tanks ages ago when we put in a pressurised water system. Our mains water pressure is very poor but this sorts out that problem so no shower pumps are needed and we get good pressure on all taps. The hot and cold tanks are now in a corner of our garage and never give any problems.


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