is rainwater safe to drink

How to Make Tank Water Safe to Drink

We often get asked the question ‘Is rainwater safe to drink?’

The answer is both yes and no. In its purest form, rainwater is certainly cleaner than treated water, being free from chemicals that may be added as part of your state’s water treatment program. But that doesn’t necessarily make it safe to drink, especially from your rainwater tank.

Because the problem isn’t the rain itself… it’s what comes into contact with the rain on its way down.

Pollution and dust, decomposing plant matter, insect waste, and even bird droppings can all attach to our precious H2O, making it pretty dirty by the time it reaches your tank. Especially if you live near factories, power lines or paper mills, rainwater can become polluted with an array of environmentally toxic chemicals. 

In addition, further unwanted pollutants can seep into the water when it’s sitting in your rainwater tank, making it downright dangerous to drink. 

Fortunately, there are various ways to make rainwater safe to drink. 

Methods for purifying tank water

When harvesting rainwater for human consumption, an additional purification system is needed. Depending on your rainwater tank setup, this could be as simple as some mesh screens, carbon filters and occasional chlorine treatment… or it could involve a more complex system such as membrane filtration.

Let’s take a quick look at a few methods.

Chlorine treatment

Chlorine is a cost-effective and quick way to purify water, particularly where large bodies of water are stored. But it can leave behind potentially toxic by-products. 

Anyone who has ever been to a public pool can likely remember the smell of chlorine. Many people end up with red or sore eyes from contact with chlorine too. 

So although it is a great general disinfectant, it doesn’t kill every kind of contaminant such as certain viruses. Additionally, chlorine can leave an unpleasant aftertaste in water. Activated carbon filters can combat this.

Ultraviolet light treatment

UV light has been used in Europe for over 50 years and is a relatively safe method for disinfecting smaller amounts of stored water. UV light works by penetrating a pathogen’s cell walls, disrupting its genetic makeup and disabling its ability to reproduce. 

This method of light sterilisation requires rainwater to be largely sediment-free. That’s because sediment blocks the UV light rays, reducing its sterilising effects.

The obvious advantage of UV light treatment is that it’s chemical-free. It’s also a less labour-intensive method as ultraviolet light bulbs have a lifespan of 12 months to 2 years.

Membrane filtration

This is an umbrella term used for various pressure-driven technologies such as microfiltration, ultrafiltration, nanofiltration and reverse osmosis. Membrane filtration works by pushing water through a layer of material to separate contaminants from the water, resulting in drinkable H2O.

Membrane filtration systems can become quite complex depending on the size of the membrane material’s pores. The smaller the pores, the slower – and more expensive – the system runs.

That being said, membrane filtration is the gold standard of contaminant removal, as it virtually eradicates any traces of algae, bacteria, and other sediments.

Before you start

Before investing in rainwater filtration equipment, it’s important to first make sure you’ve installed physical barriers such as gutter mesh, rain heads, flush diverters to stop leaves, debris and other pollutants from entering your rainwater tank. 

Stopping materials before they enter the system is far easier (and less expensive) than dealing with them afterwards.

Choosing the right water filtration method

There’s no perfect solution for purifying drinking water that works for everyone. Your choice depends on your water tank setup, your energy requirements, and your personal preferences. It’s also important to remember that some methods carry an environmental cost in terms of chemical by-products. 

Also, as the owner of the water purification system, it’s your responsibility to maintain it. So your choice will also depend on the amount of physical attention you are prepared (or able) to give to maintaining your system. 

If you’d like some expert advice to help you choose the right system for your needs, the friendly team at ASC Tanks are just a phone call away. We’ve been helping Australians save money and help the environment by installing rainwater harvesting systems since 2007.

Get in touch with us at ASC Tanks on 1300 229 606

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