Surely the cheapest hot water system there is!


Hot water from the outset was an absolute necessity because I’m not good at cold showers.  And seeing I hadn’t worked out all the options, I certainly didn’t have a long-term plan.  So I wanted the cheapest, fastest solution which I wouldn’t have any hesitation in just throwing away or recycling after a month or two.

So here’s my R130 hot water system!  Can that be beaten price-wise?  It’s 100 metres of the cheapest 16mm irrigation pipe, coiled flat on the ground in a circle as tightly as I could.  It has a diameter of 1.8 metres but could be a little less.

Hot water coil
The hot water coil. It was neater before a storm and strong winds, so the hothouse cover is probably a necessity. 
It needs to be tidied up again so that all the piping is fully exposed to the sun.

As it is now, it produces about 16 litres of water at over 70°C+ every 20 minutes on a sunny day, far more than one needs for a shower where the maximum usable temperature is below 49°C.  So with cold water mixed, I’ve yet to run out of warm water.  I think it works incredibly well.

I’m still want to obtain or make a very-well insulated storage tank — overseas, these tanks only lose 1 – 2°C every 24 hours in Scandinavian winter conditions.  If I can store 80°C water and it only loses 1°C a day, a big tank will stay above that shower-happy 49°C for 31 days… theoretically.  And surely there will be at least one sunny day in that time.

With the storage tank, that simple 100m of coiled pipe can produce around 330 litres of hot water a day.  At no cost!  And 330 litres = 55 showers, and more when you add cold water.

My temporary hot water system isn’t finished yet.  When the south easter blows, it doesn’t heat up nearly as much and the temperature at the tap must be around 49°C — because a shower needs no cold water.

So I am going to build a stone berm around it, to protect it from the wind, to create a heat trap.

And I am looking for a sheet of clear or translucent plastic to cover the coil, to create a hot house.  Two old plastic shower doors will probably do the trick, supported at the centre of the coil — to keep it just above the piping — by a brick or block of wood.  There will be a wooden frame around the coil to support the plastic at the edges.  Or maybe the clever people at Duraplastic have a solution?

There is the chance that with the hot house and heat trap, the water could become too hot for the pipes.  I haven’t had any pipes popping yet but the jump in heat will be significant.  I will need a small pump that transfers hot water from the coil to the tank whenever the temperature of the coil’s water reaches a certain level or is higher than that of the tank’s water by a certain amount.

Any tips if you want to make one yourself?  Coiling the pipe was a nightmare because it kinks so easily.  I tried coiling it when it was cold and after it had got warm in the sun, and it kinked just as badly.  The trick is to fill it with water first and the water pressure stops it from kinking. (The idea came from the bending spring electricians use to bend conduits.)

If I had to do it over, I would heat the central start of the coil with a blowtorch to get an even tighter first two coils.  That will set rigidly and make what follows much easier.

Another tip is where you buy the irrigation pipe.  Builders Warehouse only sold 20m sections while agricultural and irrigation supply companies sell 100m sections.  Joining sections just increases the chances of the connections popping when it gets very hot.

The coil doesn’t have to be on a sheet of galvanised iron.  I just had a lot of galvanised sheets lying around.  It’s there because one doesn’t want weeds or grass growing between the pipes.  So that is something you need to address.

Come back to see a pic of the final system with berm and plastic — I’ll add it as soon as it has been done.  I’d love any suggestions or comments.

So why are you paying Eskom for your hot water?

 


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