Poly Solar Hot Water For $100

Owen Paynter, of Katanning in southern Western Australia, is a part-time inventor, who has developed a brilliant solar hot water booster: cheap, long-lasting poly pipe connected to a normal electric or gas hot water service. Owen had previously owned a normal roof mounted tank! solar panel system and found the cost of keeping the water hot in the colder months too high, as was the water loss in the hot months as water poured through the relief valve on very hot days. When he built another home a few years on, he went to an electric storage hot water service (HWS). Poly pipe is non-corroding and cheap, so here is how he did it.


by Owen Paynter

Katanning, WA.

Two years ago I looked at a piece of high-pressure poly pipe sitting in the shed, left over from the 200 metre roll used to connect the home to the mains water meter when I built in 1994 - five acres requires a home be situated as centrally as possible for peace and quiet and hence a longer run for power, phone and water.

I remembered how hot the water supply to the home had become before I buried the supply poly. It was lying on the ground after connection for a few weeks due to a wait for the energy to dig the trench - yes, by hand, I may brag. I was fitter in those days: building five acres into a residence, and planting hundreds of trees and establishing gardens, kids' play area etc.

I thought of how great it would be if I could connect poly up to the HWS and save on power by using the sun's free heat.

 How Owen did it

On my Rheem 50 litre electric storage HWS, I removed the cold water inlet and the pressure relief valve from the heater and then I fitted brass 'T' fittings to allow the water to circulate from the cold lower part of the storage tank into the poly pipe and then back into the tank up higher. The pressure relief was re-fitted into the top 'T' fitting.

I laid the poly on the north-facing lawn area at the rear of the home, because this is where the HWS is (close to the kitchen sink and bathroom). The lower cold connection

has an elbow to allow the poly to be run at the correct angle as my HWS is mounted 1.2 metres above ground level on a platform screwed to the outside wall.

I used a stainless hose clamp on each poly connector because they are plastic threaded. The hose clamps keep the plastic from flanging out. Before I fitted the clamps I suffered small water leaks at the joins that even double thread tape wouldn't stop for very long.

 List of fittings

To connect my Rheem 50 litre system to poly pipe I used the following:

3 x 3/4 inch x 1/2 inch brass connectors male.

2 x 1/2 inch brass "T's" female.

lx 1/2 inch x 3/4 inch brass 90% elbow female.

1 x 1/2 inch brass joiner male.

2 x 3/4 inch brass caps.

2 x 3/4 inch female x 25 mm HP poly connectors.

40 metres of 25 mm OD high pressure poly pipe

2 x stainless 55 mm hose clamps.

2 x rolls thread tape.

Tools required

Multigrip pliers (large)


12 inch shifting spanner

10 inch shifting spanner

Plain medium size screwdriver.

Position of the poly

For the poly to work, the yard must have an area to lay the 40 or more metres of poly pipe and most importantly this area should be facing northerly of the home and not be shaded too much by sheds or trees. (Although I imagine I could run the pipe on the south and still get sun most of the day.) I was fortunate before building, in that I understood basic passive design solar principles affecting a home. I planted deciduous grape vines with trellises and stone fruit trees, and the good thing with the poly is that it can easily be shifted around to obtain optimum sun.

Circulation of water

The poly has to be slightly lower than the HWS, then the hot water rises to the higher hot water connection that is much higher on the tank. The cold water in the tank bottom automatically drops and circulates Out of the cold poly connection. Heat rises and cold drops. No pump is needed.

Even if the water in the tank is all cold and the circulating water goes the opposite, it will only do so until the water in the top section of the HWS reaches a warm temperature, then the cold water at the lower part of the tank will reverse the flow so that the heated water goes into the hot (or top) connection.

Reverse cycle

I disconnect the poly from the heater during the winter, as I find that the water is cooled too much by the poly sitting out in the cold and frost and it is cloudy a lot. Even on sunny winter days the water never got past warm. If I leave it connected past mid autumn, my power costs skyrocket.

It is easy to disconnect it. I simply unscrew the two poly connectors and fit 3/4 inch threaded brass caps over the outlets. I roll the poly up and cover each end with tape to stop dirt or insects getting inside and store it in the shed until early September. I remember the huge winter power bills years ago, when I had the roof-mounted solar system and I imagine if I could have disconnected the solar panels somehow I would have had vastly more reasonable bills. It is cold up on the roof on frosty and cold nights in winter.


In the southern part of Australia where I am, I save well over $30.00 per month on my power bill for the seven warmer months that the poly is connected, giving a yearly energy saving of at least $210.00. I have a switch installed in the kitchen connected to my HWS that lights up red when operating and I only switch it on when needed.

I save 3.6 kwh when I use my poly solar booster. Because I turn the electric HWS on for an average of three hours a day in winter, and only one day in 20 in the warm months, I save: 3.6 kwh X 3 hours = 10.8 kwh X 200 days) which equals a saving of 2,160 kwh.

On 12 December last year I needed an early morning shower at 4:00 am. I only turned on the electric booster for 15 minutes because the water was still warm from the 'poly boosting' the day before. This was the only time so far that summer I had needed the electric boosting. I think my summer poly solar boosting equates to about 5 per cent electricity and 95 per cent sunshine.

On cloudy days, it might be hot enough to shower, but to wash up the dishes I can use the kettle or hit the switch on the electric HWS for 15 minutes. Fifteen minutes to boost it is a cost of just under 1 kwh, but the 1600 watt kettle will use about three minutes of power or just 0.08 kwh. I go for the kettle usually - unless a lot of plates need washing!

Poly solar kits

It is fairly simple to set up the poly pipe to connect to your heater if you are well versed with basic plumbing, and love working things out for yourself and have time to spare. It is like anything though, and if you are not plumbing inclined, or perhaps live a distance from readily available plumbing supplies or are pressed for time, I sell the poly solar installation kit Australia wide. It includes complete instructions with tips and suggestions on layout of the poly, brass elbows, fittings, plugs (for winter disconnection), brass pressure relief 'T' extender and tank connector, adapters and pipe connections and thread tapes - all you need obtain is the poly pipe.

If you are on mains water you must use 25 mm outside diameter HP poly pipe. If you are on tank lower pressure water supply, you can use normal rural poly of 3/4 inch (19 mm) inside diameter.

Photographs from article are reproduced below


Owen also offers a book...TO

Check this out from his website as above.

The article originally appeared in the

 March - May 2001 - EARTH GARDEN and is reproduced here with permission of author Owen Paynter who supplied me with the photographs as well.

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