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Thread: What is your loft water tank lagged in?

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    HEXUS.timelord. Zak33's Avatar
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    What is your loft water tank lagged in?

    Because for some reason mine is lagged in bubble wrap. Loose, not tied... just a bit wound round.

    It's not even special bubble wrap.....it's not even that rubbish foil covered wrap that's nto real foil and wears of....

    it's just bubble wrap.

    /more expense.....

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    The late but legendary peterb - Onward and Upward peterb's Avatar
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    Re: What is your loft water tank lagged in?

    Very little. Its a large volume of water, and even if it did freeze on the surface, its unlikely to split a cold water tank. General theory is that if you remove some insulation from underneath the tank, there will be enough heat leakage through the ceiling to stop it freezing unless you are away for an extended period in winter and leave the heating turned off, in which case turn off the water and drain the tank. (which I would do anyway, regardless of how well the tank is insulated - insulation isn't perfect and doesn't introduce heat.

    The supply and feed pipes are another matter though - they do need lagging as they contain a small volume of water and are susceptible to freezing in prolonged cold weather when conditions in the loft might drop below freezing.

    My tank has some fibre insulation held on with black plastic and a lid. It is also next to the heating header tank, which is also lightly lagged, but will also introduce a bit of heat into the loft space.

    Of course, the further north you go (generally) the colder it gets in winter so you may need to adjust things accordingly. In that case you might put insulation in between the roof rafters to reduce heat loss through the roof itself which will keep the attic a bit warmer. You might then consider heating tape round pipework.

    Or you could have a small low wattage tubular (100 watts) heater linked to a frost stat set to (say) 3 degrees under the water tank to provide a bit of heat if temperatures do fall that low. (In the 'old days' you might have used a 100 watt filament lamp to do the same thing, but they are hard to find now.

    (And bubble wrap is a good insulator - it is just small bubbles of air, and air is a poor conductor of heat. Sae principle as conventional insulation and warm clothing - trap the air in place. So its probably good enough. Gardeners use it to wrap tender plants in winter)
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    root Member DanceswithUnix's Avatar
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    Re: What is your loft water tank lagged in?

    Quote Originally Posted by peterb View Post
    General theory is that if you remove some insulation from underneath the tank, there will be enough heat leakage through the ceiling to stop it freezing unless you are away for an extended period in winter and leave the heating turned off,
    We have no loft insulation just under the tank. The thermostat is digital, so if the heating is turned off at the thermostat (so boiler enabled on the timer but no demand from the thermostat so it stays off) a safety system kicks in if the temperature drops too low, something like 3 or 5 degrees, setting a safe low non freezing temperature that the house shouldn't ever drop below.

    Actual water tank has some sort of old lagging which appears from the bits that have split open to be something like loft insulation in a bag, and strips/bags of that are duct taped to the side of the tank. There is no lid, just a few thin planks of wood across the top to keep the insulation bags from falling in. Bubble wrap sounds like a nice improvement

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    HEXUS.timelord. Zak33's Avatar
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    Re: What is your loft water tank lagged in?

    tanks should have NO insulation under the tank DancewithUnix. As Peterb says, the heat from the house below it is what stops it freezing.

    As for a large voume of water not freezing... twice in my life loft tanks have frozen on the surface from lack of insulation (not enough to split) so I like to keep it lagged and not with bubblewrap so the toilets still flush etc

    But I don't see bubble wrap as a good insulator as polythene itself is a bad insulator. It conducts heat rapidly. The air pockets are good, I agree, but the reason lofts are not insulated with bubble wrap, and are instead insulated with lagging/fibre is because its better than polythene.

    I wll be looking to roll lagging over the whole tank and leave the area under it clear.

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    Re: What is your loft water tank lagged in?

    The toilets shouldn’t be flushing from the cold water tank, all that should be supplying is the hot water tank. Polythene is a reasonable insulator, it’s just thin in bubble wrap, but several layers of bubble wrap will be effective, if a bit bulky.

    Water is densest at 4 degrees C so as water cools it sinks to the bottom of the tank and forms a wa4mer later there - which is why ponds etc don’t freeze completely unless it is very cold. So freezing will always start on the surface, but it is relatively rare for a plastic cold water tank to freeze as the plastic has enough give in it.

    It isn’t something I worry about in my house, and my tank is on a plinth above the insulation in my attic. (I’ll have a look to see if there is insulation under the plinth when I get home)
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    Re: What is your loft water tank lagged in?

    Quote Originally Posted by Zak33 View Post
    tanks should have NO insulation under the tank DancewithUnix. As Peterb says, the heat from the house below it is what stops it freezing.
    Erm yeah, that's what I have, or rather haven't

    It wasn't like that when I moved it, the loft was quite well insulated including under the tank, just not the tank itself. Far from ideal!

    Quote Originally Posted by peterb View Post
    The toilets shouldn’t be flushing from the cold water tank, all that should be supplying is the hot water tank.
    Eh? All non potable water should be going from the tank, so I expect the kitchen sink to supply drinking water from the mains but the shower, bath, toilets and upstairs sinks to come from the tank. That gives a nice steady water pressure regardless of what the mains pressure is up to.

    Unless you have a fancy grey water system, in which case you flush today with what you bathed in yesterday, but I don't know anyone who actually has that.

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    Re: What is your loft water tank lagged in?

    Quote Originally Posted by peterb View Post
    The toilets shouldn’t be flushing from the cold water tank, all that should be supplying is the hot water tank.
    all toilets in a house with a cold tank should have at LEAST one toilet that flushes from the tank, because if there is a mains water issue/ cut off, the hygiene of the house is maintained, with one useable toilet.
    Ditto bath cold taps should also run from the tank so that hot water from the hot tank can be balanced with cold from the main tank for family hygiene.

    The issue of tank/mains then gets tricky on bathroom sink taps.

    I'd rather have fresh mains to the sink taps so I can drink that water at night. Mty old house I had repiped to do that in the two upstairs sinks.
    But my new house, all 3 bathroom sink taps run from the tank, making it in theory undrinkable.

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    Re: What is your loft water tank lagged in?

    I can sort of see the logic with toilets, but baths/showers only if they have mixer taps to avoid high pressure mains preventing hot water flow. Not sure why you think it is more hygienic for bath taps to be fed from the cold water tank rather from mains water.

    Certainly every house I have lived in has had cold water taps (and toilet cisterns) fed from the cold water inlet. And that theory fails in houses with combi-boilers where there is no main cold (or hot) water tank.
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    Re: What is your loft water tank lagged in?

    Quote Originally Posted by Zak33 View Post
    What is your loft water tank lagged in?
    Cobwebs...

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    Re: What is your loft water tank lagged in?

    Just checked my tank. Its insulated top and sides with about 30mm of some material encased in black polythene. The tank stands on an 18mm plywood plinth mounted about 30 inches above the ceiling rafters. the area under the plinth is insulated. It is quite a big tank, and sits next to the smaller heating header tank which is similarly insulated. And all taps and toilet cisterns are fed from the mains supply, only the shower has a feed from the cold water tank (at a point lower than the feed to the hot water tank so if the tank empties, hot water is lost first.)

    I'm quite happy with that!

    With regard to direct or indirect systems, this clarifies the pros and cons.

    https://victoriaplum.com/blog/posts/...-water-systems
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    Re: What is your loft water tank lagged in?

    Quote Originally Posted by peterb View Post
    Not sure why you think it is more hygienic for bath taps to be fed from the cold water tank rather from mains water.
    Only in the rare event that you lose your water supply for a day or two, then keeping the ability to bathe is nice

    But otherwise, unless you keep dead pigeons in your water tank it should be moot as to whether it comes from the tank or the mains. But generally I think it is about keeping a steady head of pressure, mains pressure can vary quite a lot during the day whereas the height of your house tends to be fairly constant.

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    Re: What is your loft water tank lagged in?

    ref bath tap from loft tank, what DanceswithUnix says is right.

    Quote Originally Posted by peterb View Post
    Not sure why you think it is more hygienic for bath taps to be fed from the cold water tank rather from mains water.
    .
    I meant for bathing / showering

    A) If you lose water for even 12 hours, having a bath with both hot AND cold is a good thing. If you can only get hot water from the hot tank you're snookered until it cools
    B) Many showers run from the bath taps. Having equal pressure from both makes it work best. Mains water pressure is often way higher and then getting a good safe temp is hard. Plus if someone uses a mains tap somewhere in the house, the water pressure drops and the person gets burned in the shower.

    I'd love to have mains water to my two upstairs sink taps. I will sort it when budget for replumbing is viable. But I don't think I'd want mains water to the bath or to the toilets.


    As an aside... I've lived in my house for less than 2 weeks and I have a letter today saying the water will be off for between 4 and 8 hours next Monday.

    Utterly coincidental but it does show it happens.

    I'm going to lag my tank like PeterB's now....lots over it and round it

    Quote Originally Posted by Advice Trinity by Knoxville
    "The second you aren't paying attention to the tool you're using, it will take your fingers from you. It does not know sympathy." |
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