Those immortal words from Coleridge’s “Rime of the Ancient Mariner” come back to me quite often these days.
“Water, water everywhere and not a drop to drink.”
He was, of course, talking about being surrounded by sea water, a fate being suffered by more and more houses in Bali. Make no mistake we are facing a water crisis that is getting worse every day. As more buildings are built, more bores are drilled to suck water out of a water table that simply cannot cope and drawing seawater further and further inland.
We should think carefully about the liquid that makes up 90% of our bodies, after the oxygen we breath, water is probably the most important thing keeping us alive. In spite of this there are those who own water companies who believe that everyone should have to pay for their water. “How dare people expect free water, anyone would think it just falls out of the sky”…. But just a minute….. It does doesn’t it?
Humungous volumes of soft, beautiful, pure water falls from the heavens above onto the earth beneath. As it lands it absorbs all the dead rats, fertiliser, mosquito chemicals and dog poo we have lying around, it then seeps into the ground where it picks up a few nasty bacteria from septic tank leakages and the neighbour’s pig sty. As it travels lower it absorbs a few heavy metals: lead, cadmium, mercury and the like followed by calcium and manganese which makes it hard before entering the water table proper where it may well mix with some sea water making it saline.
We now drill a hole up to 50 metres deep, install a pump and, at great expense, pump this toxic brew back up to the surface where, at even more expense to say nothing of inconvenience, we pump it through god knows how many filters, softeners and conditioners to make some feeble attempt at removing all the noxious contaminants it has collected on its adventure through the earth. High pressure pumps drive it through filtration systems, using electricity and an endless supply of filter cartridges and membranes which may need changing on a monthly basis. The hard water leaves “scale” everywhere blocking our water heaters, leaving fur in our kettles, white marks on our glass, thick deposits in our washbasins, toilets and the tiled walls and floors of our bathrooms and leaves our clothes and bedsheets grey and as crusty as a fresh baguette.
Now that’s a really clever way of doing things isn’t it?
Might it not be a good idea if we collect the water as it falls from the sky and store it in its pure, unadulterated form ready for use at a later date?
We are, of course, talking about rainwater harvesting.
But is it possible? Is it viable?
Yes, of course it is but we will need:
- Some gutters on our buildings to collect the water.
- Tanks to store it in.
- A little engineering magic to allow the rain to wash the roof off before we start collecting water.
- Enough roof area to collect the amount of water we need.
- Some basic filtering to stop leaves and the like getting into the tank.
- To keep the water in the dark so that algae doesn’t grow in it.
- A small pump to supply the water to our taps.
Other than that it is all fairly straightforward really.
To make such a system we will need to answer some basic questions:
- How much water will we need?
- How much water can we collect?
- How much water do we need to store?
If we are careful with our use of water an average couple can expect to use around 170 litres of water per day or 62,000 litres per year. See the water usage calculator at www.mrfixitbali.com/water/water-usage-bills-and-charges/water-usage-calculator.html.
Denpasar averages around 1,650 mms of rain a year giving us 1,650 litres for each square meter of roof area. That’s 98,000 litres per year from a 60 square meter roof. Obviously rainfall varies considerably and, generally speaking, we will get more rain on higher ground though it’s as dry as a camel’s buttocks on the bukit.
We will need enough storage to get us through the dry season and, rather like the cash flow in a business we need to plot our expected collection and usage of water through the year. We also need to allow for a storage “buffer” to get through those exceptionally dry years.
The storage system needs to be carefully designed to protect our precious water from contamination.
Finally, if you are unable to stop that overzealous pembantu’s daily habit of throwing a single towel into the washing machine and setting it on “extra long two hour wash with copious rinsing” then I suspect rainwater harvesting will not be for you.
If you are interested you will find more information including calculations and storage on the webpage at www.mrfixitbali.com/water/water-supply/rainwater-harvesting-256.html or you can contact us through the website.
Previous “Fixed Abode” articles can be found subject indexed on our website at www.mrfixitbali.com. Opinions expressed are those of Phil Wilson. He can be contacted through the website or the office on 0361 288 789 or 08123 847 852.
Copyright © 2019 Phil Wilson
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