Friday, October 26, 2007

74 The stepping Backwards law


We started to worry about our availability of drinking water. Nimmitabel and Cooma both had to truck water in from the Murrumbidgee for general use and Goulburn had run out altogether, but we had no option but to look after ourselves and not depend on any authorities. There was still some water in stagnant pools in the river which the platypus could almost walk on, that we could tap off. Also, we had about 4000 litres of rainwater stored, and that’s a lot of drinks, but we didn’t know how many more years might pass before the next rains. Others had many more tanks than us in all sorts of shapes and sizes. Some even collected tanks to store their firewood in, out of the rain.

We ordered a new tank. It was 18,000 litres capacity and about 2.8 metres high, but would unfortunately be delivered empty. I calculated the rainfall needed to fill it. It went something like this: one mm rain on 1 square meter of roof is 1 litre of water. The roof I was going to collect from was around 10 m by 10 m, so 100 square meters and a second slightly higher roof 30 metres from the tank would give me another 80 m², totalling 180 m². I was going to need 100 mm rain to fill the tank, just 4 inches. In a normal year we might get that in 2 months but this period was not normal. Still we would be able to collect any dew that formed on the corrugated iron rooves and that would be worthwhile.

I had to work out how to move the water from the distant roof to the tank. John suggested taking it to ground level in a down pipe and running it in a trench the 30 metres to the tank and then raising it back in an up pipe. This would work well as long as there were no very low temperatures to freeze the residual columns of water in the up and down pipes that would be 2.8 metres high when the tank was full. I decided to keep the pipes above ground and falling all the way to the tank. If it really rained hard and the 30 m long 100 mm plastic sewer pipe was full, it would be carrying over 200 kg water; that’s a pi (22/7)*radius squared(5*5)*length (3000) thing, all in cm remembering a 1000 cubic centimetres is a litre and that weighs 1 kg. With so much weight the pipe would bend and break in the first downpour. This meant it had to be strongly supported by a bridge along its length.

I followed my principle of don’t buy new if you can adapt old so started the bridge project by looking through my piles of rubbish for adaptables. Up came a good number of steel star posts that I had recycled when I dismantled a fence. I could fasten three end to end but overlapped together, using bolts through the holes that normally take fence wires. Putting two of these three-long droppers side by side and attaching them 30 cm apart with bolts and some bits of recycled dexion angle iron would give me one upright for a bridge structure to carry the pipe. I made two of these paired uprights in about 20 minutes and erected them first hammering each bottom single dropper into the ground. Using the sheds as end supports the overhead pipe looked pretty stable on its four props joined by a couple of lengths of fencing wire. Of course it wouldn’t have passed any regulation. I decided to sit back and wait for the rain.

Close in importance to ‘Sod’s Law’ which says that anything that can go wrong will, is the ‘Stepping Backwards’ Law. The stepping backwards law says that if you start a job, you won’t be able to complete it until you have fixed something else that is needed for the job. Gordon had the lost-tool-problem that prevented completion of many jobs. He had to go to Bombala to buy a replacement. He might run out of petrol on the way or have a flat tyre and someone had borrowed the spare. The primary job might have ten other jobs stacked under it.

My amazing water collecting system followed the stepping backwards principle. First the gutters on both sheds needed significant attention as they ran the wrong way and leaked as quickly as they filled. I had to rebuild the roof on one of the sheds and the wall that carried the guttering because the timbers had rotted in places. Step backwards one square. When I started on the guttering on the second shed I found it was full of fine white fibres. These were from the eight full-width fibreglass skylights or windows that were no longer letting much light through. From ground level they just looked dirty, but at eye level they were so deteriorated that I could push my finger through. Step backwards one square.

I quite like eating foods that have a little crunch, except green beans, but rainwater with crunch had no appeal. The skylights had to be replaced with clear polycarbonate. This meant a trip to Canberra but at least I also learnt that the only way to fasten polycarbonate sheets to the top of the car is in a tight lengthwise roll; then they don’t buckle and blow away but act like a strong pipe. There is so much to know.

The standard lengths of polycarbonate were 20 cm short, a consequence of going from imperial measurements to metric so that required some adaptations to the plan and a further step backwards.

Once all the skylights were replaced it seemed I had stepped backwards far enough and forward movement was suddenly meteoric as I fell off the ladder. But there were no consequent problems. In fact it started to rain. It rained just gently to test and savour the feeling, more like a mist than rain. Apparently it liked softly touching the dry crackly grass and after a while it decided to search out more dramatic sensations. It poured. Three inches were delivered then it became bored. I have no idea why it always rains in inches here, but it really does. It stops at half an inch, or an inch, or multiples of an inch, but never at millimetres unless it is being coy when maybe 2 mm might fall.


I tapped on the tank to see whether my calculations were correct. It should be three quarters full. At three quarters it sounded deeply hollow, at half it sounded slightly less deeply hollow but at a third it sounded dead. It was one third full and my calculations were way out. Still who cares, we had 1000 gallons of captive pristine rainwater, worth $4000 if we could sell it in those tiny plastic bottles that are in the supermarket. Better still the river was starting to flow and the platypus no longer had to walk on water. The drought is over some said very quietly to themselves.

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