Water tank heaters

[Otter Spotter]

I want insulate and put heater pads on my underslung water tanks (drinking and grey) I have seen heater kits costing £240 with frost sensors, my question is can I not just have the power to the heater pads on a switch so I can manually switch on and off when I think it may get cold enough to freeze ? And if I use the foil backed insulation do I really need heater pads on the tanks ?

 

[autorouter]

And if I use the foil backed insulation do I really need heater pads on the tanks ?

Anything that does not generate its own heat will eventually get to the same temperature as its surroundings. Insulation slows down the flow of heat, but can never entirely stop it. An insulated water tank will eventually freeze if the surroundings stay below freezing point for long enough.

If the air temperature is above freezing for much of the day, but dips below freezing for a few hours overnight, then lagging/insulation might slow down the heat loss so that the tank doesn't freeze.

If the MH is in storage, and the air temperature stays continuously below freezing for more than a couple of days, then even the best insulated tank will start to freeze.

my question is can I not just have the power to the heater pads on a switch so I can manually switch on and off when I think it may get cold enough to freeze ?

The problem with a manual switch rather than a sensor/frost stat is simply that it's so easy to forget to switch the heater on, and also difficult to decide when to switch the heater off. And the consequences of getting it wrong, even if only once, can be expensive frost damage.

 

[Two on Tour]

I used these as tank heaters stuck to the bottom of both the fresh and grey water tanks.
https://www.ebay.co.uk/itm/Self-Adhesive-Thermo-Heating-Pad-12V-15W-35-40degC-S-A-Pad/121744329623?ssPageName=STRK:MEBIDX:IT&_trksid=p2057872.m2749.l2649

To stop the grey waste dump pipe freezing I used trace heating cable from the tank to the dump valve.
https://www.ebay.co.uk/itm/12V-Self-Regulating-Heat-Trace-Cable-for-Freeze-Protection-on-Cars-and-Trucks/263948589172?ssPageName=STRK:MEBIDX:IT&_trksid=p2057872.m2749.l2649

Each tank has the temperature of the heat pads controlled by a digital thermostat with the thermocouple placed on the side of each tank about 60mm from the bottom of the tank.
I have these set to come on at 3 degrees and go off at 5 degrees C.
Amazon product ASIN B008KVGWT4
I insulated the tanks with double layer bubble wrap insulation which has a foil coating both sides.
Amazon product ASIN B011PJSR22
I taped the corners and edges and stuck the top edges of the insulation to the tanks with T-Rex tape which stick like the proverbial sh*t to a blanket.


The grey waste dump pipe I insulated with Armaflex pipe lagging.
https://www.pipelagging.com/pipe-in...ulation-lagging-black-nitrile-foam-class-o-2m

 

[Nixdorfer]

Those temp controllers look handy. Prob order one later

 

[Theonlysue]

Problem might be pads at the bottom of the tank and ice forms at the top of the tank.
Also, the water can freeze in the pipes so water cant move anyway.

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[HandyAndy]

Problem might be pads at the bottom of the tank and ice forms at the top of the tank.
Also, the water can freeze in the pipes so water cant move anyway.

If you heat the bottom it will move to the top itself. Thats how science works ??

 

[Langtoftlad]

I want insulate and put heater pads on my underslung water tanks (drinking and grey) I have seen heater kits costing £240 with frost sensors, my question is can I not just have the power to the heater pads on a switch so I can manually switch on and off when I think it may get cold enough to freeze ? And if I use the foil backed insulation do I really need heater pads on the tanks ?

It's basically what Wildax do.
Lagged tanks & manual switches.
Though I've never really used the tank heaters.
I think it would have to be really really cold for a long time for a 100 litres of water to freeze.

 

[Theonlysue]

@handyindeed.
But the ice is very cold and the heat pads dont give out a lot of heat.
Been there got the t shirt ?

 

[Two on Tour]

@handyindeed.
But the ice is very cold and the heat pads dont give out a lot of heat.
Been there got the t shirt ?

The trick is not to let the ice form in the first place.
Maybe your heat pads are not up to snuff, but ours get nice and toasty.

 

[Theonlysue]

Speak to Autosleeper.
Had their winter pack on.
At Shrewsbury a couple of years ago at fun rally. Was minus degrees and I wasn't alone with frozen water Terry lol

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[Two on Tour]

Speak to Autosleeper.
Had their winter pack on.
At Shrewsbury a couple of years ago at fun rally. Was minus degrees and I wasn't alone with frozen water Terry lol

Why would I want to talk to Autosleeper ? I fitted my own gear I know it work on my van, the OP asked the question and I tried to help by answering.

 

[autorouter]

If you heat the bottom it will move to the top itself. Thats how science works ?

Water is very common and familiar to everyone, but it has one property that's almost unique. Normally when water is heated it expands, becomes less dense, and therefore tends to rise through the surrounding colder water. As everyone knows. Equally obvious, when water cools, it sinks for the same reason.

However, when water is below 4 degees C, but above zero degrees C, it contracts when heated, and expands when it cools. This is the exact opposite of expected behaviour, but this is precisely the temperature range we are interested in when protecting from frost.

So it's not totally obvious that a heater on the bottom of the tank will always heat all the water above freezing.

However you will be pleased to know that, even with all these complications, as long as the heater can keep the bottom of the tank above 4 degrees C, then there is no danger of ice forming.