At the top of the hill are three old steel tanks. Not the sort you drive around in looking for people to kill, the sort that stores water. In other words, tanks for life not tanks for death.
Two of them are nothing but broken down old relics from which we have started to harvest the left over sections of still-useful-for-something curved corrugated iron. For instance a cross-sectioned slice of the tank that has the smaller loin-fruit’s bike leaning against it will soon be a 400mm deep aqua-garden, once lined with pond liner and otherwise set up.
The tank in the middle ground his until recently continued to serve as a header tank for the irrigation. It has certainly earned its keep, being lined with a tank-bladder it was still watertight even after 20+ years. However tanks are a bit like some old people; their bladders eventually fail and begin to leak in unfortunate ways and just as you wouldn’t want an embarrassing stain on your trousers whilst queueing in the market, nor do you want to lose 5000 litres of valuable water.
To be frank the old tank stank and it was time for a brand new spankin’ tank thanks.
The replacement tank is 10,000 litres capacity and is constructed of food grade plastic. Though we are of the opinion that in general the phrase “food grade plastic” is akin to “military intelligence” the reality is that this baby is going to be used for irrigation only, and steel tanks are plastic lined anyway. The other alternative; concrete tanks are too cost prohibitive for this application.
Needless to say a 10,000l tank when full weighs a few tens of kilos over ten tonne. When installed 40 metres or so up the hill from where you’re having a Pimms and Lemonade on a hot day you want that baby to be unlikely to suddenly tip and roll down at you. You also don’t want all that weight sitting on a sharp rock, or you’ll soon have a second leaking tank!
The “pad” for the new tank has been bordered, levelled and packed with fine grit road mix to create a reliable surface that will further harden and bed down as time, pressure and moisture settle it.
Once the pad is prepared the next step is to recruit some helpers in the form of She-Who-Puts-Up-With-Being-Recruited-Into-All-Sorts-Of-Crazy-Schemes-Of-Mine and the local neighbour. Helpers are necessary for two reasons; firstly because large tanks are heavy and cumbersome even when empty and they like to roll down hills, and secondly because you need someone to look at the prepared pad and say “That’s not big enough!” so that when you ignore them, drop the tank into place and demonstrate that indeed it is perfectly sized you can gloat at their ignorance and scoff at their doubt.
Once filled from the dam (using the trusty Davey pump) this tank holds enough for about 6-8 weeks worth of irrigating the vegies. The water is delivered to the vegie garden taps at approximately 52psi (358kpa) static pressure of head (approximately 40 metres of drop). For reference standard domestic supply is about 58-72psi so whilst this is close to the the low end of the scale we’re pretty close to a standard tap pressure.