If you turn on the tap and get water from a town water supply then you rather take fresh water for granted. Or at least, in New Zealand you do.
But when we moved to our small house in a rural beach location we started drinking rain water, stored in our own tank. That’s brought a whole new awareness, from questions about health and safety, to a far better understanding of the connection between rain and the water we use.
After a heavy rain I enjoy taking long showers, knowing the tank has been topped up. In the middle of a dry summer we take care to use water more sparingly.
We’re also more aware that if the power goes off, as it often does around here, the pump on the tank won’t work and so nor will the taps. Also, the toilet won’t flush.
In an emergency though we could take the lid off the access to the tank and draw up water in a bucket. That’s reassuring when it comes to earthquake planning.
Our house was built a couple of years ago, and while we are connected to the national electricity grid we have to collect water off the roof for drinking and household use. We have a bore and pump which supplies water we can use on the garden, but that water is not suitable for drinking.
When they built the house, the very first step was to dig a couple of holes and install tanks. One was the septic tank, on the southeast corner of the property. The other was the 40,000 litre rainwater collection tank beside the house.
Our house is 68 square metres in area and when it rains the water collects in the gutter then runs through a couple of pipes into the storage tank. For every 1 millimetre of rain we can collect around 65 litres of water.
As a guide to collection capacity, consider that each 1mm of rain = 1 Litre (L) of water per square metre (m2) of roof area, then allow a 15% wastage factor. — Roof surface & area | Rain Harvesting.
That works well when it rains a lot in winter, but in summer things tend to be dry round here and the usual pattern is infrequent light rain. There’s plenty of opportunity to wash bird poop and other debris right down the pipe and into our water tank.
One day I was listening to Radio New Zealand and heard this on Our Changing World:
Further research into various physical methods for collecting clean roof water showed that a first flush diverter was the single most effective way of maintaining good water quality. The first flush diverter diverts the first 50 to 100 litres of water collected during a rain event, ensuring that contaminants don’t make it into the tank.
It works like this: the first rain in any spell washes dirt off the roof, down the main pipe and into the flushing tank where it accumulates. The debris falls to the bottom and a plastic ball floats on the surface. When the water reaches the top of the flushing tank the ball blocks the pipe and any additional rainfall goes back out the secondary pipe at the side and into the main storage tank.
Meanwhile, the water collected in the flushing tank slowly drips out through a tiny hole in a small disc at the top of a small pipe at the bottom. You can see how it all works in the photo above.
So that’s all been happening since about July 2015.
A couple of weeks ago we were woken by a magnitude 7.8 earthquake whose epicentre was around 250 Km away. See Shaken awake. I did walk around our house looking for damage once dawn arrived but didn’t see any problems. As far as I know, a few ornaments fallen off shelves was the only ‘damage’ we suffered.
Then the other night we had very high winds and something loudly creaking outside the bedroom window meant I slept badly. The likely culprit was our first flush diverter which is attached to the wall there.
When I checked the tank it seemed a bit loose in its moorings. When I gave the tank a push it felt very heavy and I realised it must be full. We’ve had a lot of rain recently but the tank is supposed to slowly empty itself.
I unscrewed the drain pipe at the bottom and a huge amount of disgusting, foul-smelling water gushed out. That’s when I discovered via some YouTube videos that there’s a filter inside and I’m supposed to clean out the tank and its filter every few months.
Sure enough, the filter was totally clogged and disgusting. A scrub with a dish brush and some water did the trick though.
It’s disturbing to think that all that muck was at the bottom of the flushing tank, and I hope none of it found its way out of the tank and into the main water supply. I now have an entry in my calendar to remind me to check the filter every few months.