Do I Need To Test My Rainwater Tank?

Rainwater quality is important to many of us, especially when it’s used as a drinking source. We have the potential to get sick from poor quality water, just as we would from poor food hygiene. It ultimately boils down to the storage environment, how it got there and the conditions it’s kept in. If your fridge isn’t cold enough, that chicken dinner might just give you a dose of food poisoning. If you use a thin wall plastic barrel you found, that allows light in to it and the sun heats the water up, then you’re creating an environment that bacteria will thrive in.

What About Animal Droppings In My Tank?

There’s always potential for small animals to scamper about on rooves and do their business in our catchment system. The peace of mind I have is that they would have to be in plague proportions to be able to overpower my immune system. Our bodies are wonderful at attacking bacteria that doesn’t belong inside of us. Obviously, people with weakened immune systems would have to be a bit more careful too. The other security I have is using 1mm screens as per the Australian Standards in my inlet side like a leaf eater, tank screen and a first flush diverter to direct the bulk of any droppings away from going in to my tank.

People still get concerned about contamination from bacteria like cryptosporidium, which predominantly comes from higher order mammals like cows and humans. So as long as you keep them from your roof catchment, there shouldn’t be a reason for alarming ourselves with potential problems. I think that’s a pretty easy one to deal with.

How Often Should I Clean Out My Tank?

The nature of our water tank environment is that it will build up a bio-film on the walls of the tank as well as a sludge layer on the bottom where organic matter settles over time. This has actually been shown to be a benefit to the water quality in that it gives any bacteria something to cling to, which then means it doesn’t end up going out the tap. By pulling the water from slightly above the bottom of the tank, but also not from the top of the tank, you will be drawing the best quality water out. The top layer is more likely to be exposed to light and warmth, which is the best environment for bacteria.

As a rule of thumb, cleaning out your tank comes down to how much organic matter your tank is getting in it and breaking down inside of it. If you can keep it to a minimum, then you could find your water quality is still great 5 years in. If you don’t do any preventative maintenance, have an open hole in the top of the tank and live amongst the gum trees, then you might be cleaning it every year. The short-term cost of using a well-designed rainwater harvesting system will soon outweigh the time and inconvenience of cleaning a regularly dirty tank.

How Do I Get My Rainwater Tested?

The advice I have received myself is that laboratory testing is an overkill and an unnecessary cost in a home scale rainwater harvesting system. As simple as it may sound, smelling the water to see if it has an odour can give as much of an indication of the quality, as well as looking for discolouration as an indicator. If the water smells, it’s likely to be coming from organic matter breaking down in the tank and it’s time to clean the tank. Not all bacteria are harmful to us and laboratory testing won’t always tell us which strain of bacteria it’s detecting.

So really, if your harvesting system is working effectively and you apply some level of basic filtration on the way out, you’ll get to enjoy the pure, fresh taste of rainwater, like many of us already do. I’m more concerned about the bacteria on shopping trolley’s and on money than what might be in my rainwater!

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