It was a Dark and Stormy Night…

By Doug Falconer Barkers Creek, Victoria.

It wasn't actually, but I've always wanted to start a story that way. It was actually New Year's Eve, and the little rain we were getting was the first (and last) in quite a while, and was very welcome. We're pretty frugal with water at our place - we bucket bath water to the washing machine and use dam water in the toilets (sshhhh), so even during the long drought a couple of years back, we had plenty of beautiful sweet rainwater in our 5,000 gallon (22,000 litre) tank. (The garden was another story).

So, imagine our horror when, upon rising on New year's Day and heading for the first of many long draughts of the aforementioned liquid, we found it had 'turned' overnight, and was not only undrinkable, but difficult to be in the same room with! It had an odour somewhere between the compost bucket and a teenage boy's socks, a milky appearance and a taste reminiscent of the washing up water at a Scout Jamboree of the mid-70's.

We didn't panic (honest). Okay, just a little. Luckily, our dam water is useable for everything but drinking and cooking (and even those at a pinch), as we are on friendly terms with the neighbours for ten gallons (45 litres) a week of the good stuff.

But what to do? Anyone who dropped in over the next few days had an opinion or ten. The consensus was that the light rain had washed the water (that had been stagnant) in the house stormwater system into the tank, tainting the whole thing. Sure enough, when I opened the let-of valve at the lowest point of the system, the water had that now-familiar smell. I drained the whole stormwater system to try to let it dry and sterilise.

Now I had to work out whether I could rescue the 5,000 gallons in the tank. I did a few 'home chemistry set' experiments on it, trying to precipitate out the muck. Oddly the pH seemed okay, but both bicarb soda and lemon juice precipitated out a fair but of stuff which settled.

Unfortunately the water was still undrinkable, even though it was now clear. Before I could formulate a plan to rescue the water, the forecast hinted at rain (don't you love the way they hedge their bets nowadays?), and I had to make a snap decision. After a fair bit of agony (water is precious in this neck o' the woods), I pumped the whole lot out onto the garden, which appreciated it more than I can express. Our tears probably helped too, in spite of the salt.

Those of you who have emptied concrete watertanks on bush blocks before are all smiling and nodding now, I know. Two days of sweeping, scraping, siphoning, swearing, sweating and swatting followed as Doug tried to clean the tank manually - during the heatwave. I had always done it by the truly marvellous Earth Garden funnel and siphon method (see story in EG 78, page 13) before, and what I didn't know about the bottom of my tank was just fine by me. Eventually, though, a slimmer version of your humble reporter emerged from the tank declaring it once again fit to hold water.

But it hasn't rained again, has it? The hiatus has, though, given me time to do a little research. A quick search on the Internet turned up a marvellous page produced by the Western Australian Department of Health's Environmental Health Service, entitled 'Water Safety - Is the Water in your Rainwater Tank Safe to Drink?'* It emphasises the importance of keeping a tank cool (full and shaded), dark (light encourages the growth of micro-organisms) and screened against the entry of insects, birds, animals and leaves. It recommends desludging once a year. It also lists the methods for decontaminating a tank that's gone of. This was a little late for me, but since all the methods required some kind of chemical, I probably wouldn't have done them anyway.

Doug installing the SafeRain unit at home near Castlemaine in central Victoria. Photgraph by Lily Falconer.

Most important to me though, it talked about using leaf traps and 'first flush diverters' to divert the first hundred litres or so of each fall of rain, to prevent build up of leaves, gum flowers, creosote and possum poo - on the roof and in the stormwater system - from entering the tank. The light globe over my head came on.

After looking at several units which used buckets and lengths of stormwater pipe to divert the water, all of which were difficult to configure for the amount of water I wanted to divert, I read about the SafeRain unit produced by Rosemary Church in Blackburn, Victoria. This unit has been tested by the CSIRO and won an award at the 1996 Royal Agricultural Show in Melbourne. What really intrigued me was the cunning way it has been designed. Instead of relying on collecting a volume of water which then operates a valve, the SafeRain allows water to flow through it, diverting it away from the tank. While this is happening, a small proportion of the water (roughly 0.05 per cent) is collected in an ingenious little hollow plastic ball with a gauze-covered hole in the top, and a tiny drain hole in the bottom - it looks just like one of the 'pods' in 2001: A Space Odyssey.

This ball is suspended by waterproof elastic in the middle of the unit, over a valve seat. When the ball has filled it descends and closes the valve, allowing water to back-fill the unit and flow into the tank. The elastic is on a little windlass which can be raised and lowered to change the time it takes the ball to lower, and hence the volume of water diverted. When it stops raining, the water drains out the little hole and the elastic pulls the ball back up, resetting the whole thing. Damn clever, eh?

The SafeRain is also available in models for overhead and L-shaped pipes. The Reverse-Flow model described here took ten minutes to install, and I chose to add some pipe to carry the diverted water away from the tank, to where I'll eventually build a nice little pond for the ducks. I'm sure they'll appreciate it. Now, if it would just RAIN!

*http://www.public.health.wa.gov.au/ehso3.htm

Information about the unit is available from SafeRain at PO Box 298, Blackburn, Vic, 3130. Ph (03) 9894 3302. June/August 1997 - EARTH GARDEN