Can I use a plastic loft-type cold water tank for my solar water heater?

I'm currently looking for a galvanised tank. A galvanised dustbin might be a suitable alternative, although I don't like the round shape. Such a container, new, is probably watertight, but if not, could be made so. In the interim I'm going to give it a go with a B&Q Titan overflow tank (approx 4 gallons capacity). Let's see how hot that gets!

MM

Reply to
MM
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Thanks for the advice, Bob. Gratefully received.

MM

Reply to
MM

Just as a suggestion, why not make a plywood box with some holes around the bottom. (providing you have some off-cuts) for the overflow tank to fit inside.

That way, you give the plastic tank more than abundant support even if it deforms to the state of a pond liner. The "telltale" holes would let you know if there was (not likely) a leak without showering somone with scalding water... ;¬)

You would also get the benefit of it being a 100% UV block so no tank deterioration... what else....

You could make the box even bigger (4 or 5" clearance all round?) then fill the gap with expanding foam for significant thermal insulation and yet more tank support...and... um... well, why not cut out a snug fitting "floating" lid that would.. well... float on the surface of the water hugely reducing surface heat escape yet providing a very free release of all that steam ;¬))

Most expensive addition to that lot would be a large can of expanding foam for a few £'s make sure you fill the gap in layers rather than all at once.

Just a few more ideas to throw into your experiment pot.

Cheers Pete

Reply to
Pet - www.GymRatZ.co.uk

Just as a suggestion, why not make a plywood box with some holes around the bottom. (providing you have some off-cuts) for the overflow tank to fit inside.

That way, you give the plastic tank more than abundant support even if it deforms to the state of a pond liner. The "telltale" holes would let you know if there was (not likely) a leak without showering somone with scalding water... ;¬)

You would also get the benefit of it being a 100% UV block so no tank deterioration... what else....

You could make the box even bigger (4 or 5" clearance all round?) then fill the gap with expanding foam for significant thermal insulation and yet more tank support...and... um... well, why not cut out a snug fitting "floating" lid that would.. well... float on the surface of the water hugely reducing surface heat escape yet providing a very free release of all that steam ;¬))

Most expensive addition to that lot would be a large can of expanding foam for a few £'s make sure you fill the gap in layers rather than all at once.

Just a few more ideas to throw into your experiment pot.

Cheers Pete

Reply to
Pet - www.GymRatZ.co.uk

Many thanks for the suggestions. All sound good. I bought the wood for the box today at B&Q (not too expensive for 144mm wide planks, I thought, plus exterior grade 12mm plywood). I also bought another 3m of pipe, since several have said that 3m is not enough. So tomorrow morning it's all systems go again in my garage!

MM

Reply to
MM

Since youre determined not to learn anything, lets hope something else gets you before the bugs in the water.

NT

Reply to
meow2222

and you expect people to help when you misdescribe what youre building?

Reply to
meow2222

I agree! I suspect it will spend most of its time hand hot or below, which is what the OP wanted.

Possibly true. The part of the thread I was responding to was that from the disaster freaks which implied that, as soon as the water reached boiling point, which they say it would (I disagree), the user would be maimed in an inferno of boiling water as the tank collapsed (which it wouldn't if properly supported). I made no claims as to whether it would be in the recommended operating range. As such I stand by all I said. When posters weren't saying he would be boiled to death they were saying the water wouldn't even get hot! If the OP wants to bodge up a cheap system, support it well and keep an eye on it, I don't see any reason why he shouldn't. If he starts with 3m of copper tube it may get warm enough for a wash. If it doesn't get hot enough he can add some more pipe. Were it ever to reach boiling point, or near, he would take appropriate action. It's for his use only on a seasonal basis. As I said in another post, *I* (were I to build such a thing) would probably use a galvanized tank (if I could find one) for longevity, or box in /shade the plastic tank to keep it out of the uv. This sort of project is the true nature of D-I-Y.

Reply to
Bob Mannix

I don't think that was being said. I think what was being said is that collapse is a possibility, so why not obviate the possibility from square one? And I think you're incorrect about the possibility of the tank collapsing if the water gets hot (it doesn't need to be boiling).

Reply to
Steve Firth

Mostly, these will be used and drained completely. Considering the market that it's aimed at, it may have a few days partial use and then be packed away until next year.

What you are proposing will just be continuously diluting what's inside your warm water tank.

Reply to
Dan Smithers

Hardly. You will know that I am initially using a 4 gallon plastic header tank from B&Q (until I lay my hands on a galvanised tank). 4 gallons will be all used up to wash dishes, mop the floor, get me a shave, that kind of thing. I'm not planning a Chinese laundry here!

MM

Reply to
MM

No wonder you call yourself meow!

MM

Reply to
MM

In your case I don't expect very much, which is why it is such a pleasant surprise to be proved correct.

MM

Reply to
MM

The impression I got is that you were planning some sort of continuous top-up.

the B and Q website lists Titan Wizard 25/15 Rectangular Water Tank KM15 Black as having a 68 l capacity (approx. 15 imp. gal.)

dan

Reply to
Dan Smithers

On Tue, 24 Jun 2008 10:42:19 +0100 someone who may be MM wrote this:-

I suspect that, without proper insulation, the heat losses from the tank will mean that the collector does not heat the contents of the tank very much.

It is very easy to raise the temperature of a small volume of water. That is what any solar collector does. What is more difficult is to transfer and retain that heat, so that it raises the temperature of the much larger volume of water in the store by a useful amount.

Reply to
David Hansen

My understanding, from reading up on various similar projects on the internet, is that the thermosyphon effect causes the water to self-circulate through the system, causing the water at the highest point to get hotter and hotter.

As for insulating the tank, surely it's a toss up between painting it black to attract maximum effect from the sun, or the insulation alternative? Anyway, it will be easy to add an insulation jacket around the tank as an experiment. At the moment it's all rather academic anyway, since our summer so far has been a washout. My relative in Hamburg told me yesterday they enjoyed in May-June six weeks of constant hot, fine weather.

MM

Reply to
MM

Black is also a good radiator of heat. What is the relative total surface areas of your collector and tank? The surface area of your 15 gallon tank probably is close to that of your collector, you could just shift heat from the collector to tank and loose it rather than store it...

Bright sunshine has the highest energy input but only because the incident radiation is higher. A solar thermal collector will still produce a heat output on dull overcast days.

Reply to
Dave Liquorice

On Wed, 25 Jun 2008 08:39:44 +0100 someone who may be MM wrote this:-

Indeed. However, the average temperature the water reaches depends on its volume. Put another way the smaller the volume of water the deeper the "high temperature" zone is.

The problem comes when the sun is not shining directly.

Reply to
David Hansen

It's not been that bad really - my solar heating (not DIY) has been producing 200l of 40-50 degree water for the last few weeks. You can get quite a lot of energy even through the clouds.

If you have a an insulated tank, then it will keep the heat in better when the sun goes in, or if it starts raining. Additionally, it will still be warm in the morning if there is any water left in it so the sun doesn't need to provide so much energy. The surface area of the tank is small compared to that of your pipework.

BTW Have you considered using an old radiator as a collector?

Reply to
Dan Smithers

Yes, I have seen that being used in some projects. Also the matrix from the back of an old fridge. This experiment will an on-going project and I can easily modify the system or enlarge it. If I could afford £5,000 I could get a professional system installed on the roof and piped into the house waterworks. Maybe the price will come down if the government encourages solar energy utilisation as is done in Germany. At the moment I believe companies see green energy provision as a licence to print money - for themselves.

MM

Reply to
MM

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