Is Drinking Rainwater From Your Water Tank Safe?

Rainwater is a very high-quality water source. It has been safely consumed for centuries in many locations around the world and often acts as a life-saving and invaluable source of consumable water. As such, rainwater safely harvested into a properly maintained rainwater tank provides a good quality source of drinking water.

That said, health departments in Australia recommend using rainwater for non-drinking purposes such as washing clothes, toilet flushed, watering gardens and the like. For example, NSW’s Department of Health, while acknowledging rainwater is safe to drink from a properly maintained tank, mentions that cases of illness have resulted from contamination. Based upon this, they advise that drinking public (mains) water supply as the most reliable potable water source noting it is filtered, disinfected and fluoridated.

Nonetheless, if you’d prefer the fresh, crisp taste of non-fluoridated rainwater, then this article is intended to help you understand how to be safe. It identifies three main areas you should consider to ensure your tank water is safe for consumption including: 1) Roof capture area, 2) Water tank maintenance, and 3) Water filtration.

Roof Capture Area

Before harvesting rainwater for consumption, it is important to understand the material nature of your rooftop. Rainwater can be collected from most roofing materials including Zincalume®, Colorbond®, galvanized steel and even undamaged asbestos.

You should beware of lead flashings (often found on older roofs), lead-based paints, bitumen and tar, or treated timber. These materials contaminate your rainwater, which if then consumed can cause serious health issues. Additionally, avoid collecting rainwater from parts of the roof with chimneys or roof-mounted appliances such as air conditioners or hot water system (which have overflow or discharge pipes).

Second, you should inspect your roof and gutters every 3-6 months and clean as necessary. This will protect your rainwater against pollutants including animal droppings, microorganisms, aerial chemical sprays, and air pollution (especially if in an industrial area, chemical plants and quarries). If your roof is dirty, remember to disconnect your water tank before hosing it down. For safety reasons, don’t tackle this job alone, but have someone around who can keep watch and help as necessary. Remember to also steer clear of any power lines.

Water Tank Maintenance

In addition to your roof and gutters, every 6 months or sooner it is important to inspect your tank, added accessories and tank screenings. Things you should inspect include:

1. External inspection– check external structural integrity of the tank, fittings, pump and pipes. If a steel tank it is important to keep clean of debris. Some poorly designed tanks have poles inside to support the roof, which over time often pierce through. Any cracks or holes should obviously be attended to.
2. Inlet strainer – remove and built-up leaves and clean, ensure strainer meshing is intact and that the strainer itself is fitted tightly with no gaps around side (if you have mosquitoes buzzing around your tank, then possibly this is the reason).
3. Overflow screen – keep tank overflow screens clean as they can clog up with debris over time and even cause rainwater in your tank to overflow from the top. Ensure the screens are still intact to keep out insects and mosquitoes.
4. Internal inspection– check for evidence animals, mosquitoes, insects or algae. If present, identify and ensure any access points are properly sealed and light entry is fully blocked.
5. Water diverter – if installed, inspect and test, empty any built-up leaves and debris (if downpipe diverter it can be opened from bottom).

In addition, it is recommended that you inspect inside your tank every 2 to 3 years for sludge accumulation. While your rainwater might go through various pre-tank filtration devices (such as rain heads, first flush diverters, etc.), finer bits of organic matter will nonetheless find their way into your tank. Over time, this turns into slimy and sticky substance at the bottom of your tank known as “sludge”. While sludge isn’t often harmful, it can cause problems if it gets into the water column of your tank where it can get pumped out from your tank. You can remove excess sludge by hiring a professional water tank cleaning company or siphoning it out yourself.

Water Filtration

As an added precaution against water contamination, it is recommended that you install appropriate chlorination and filtration at taps where water will be used for drinking or in cooking. It will still taste fresh and crisp, but also helps to ensure heavy metals are removed.

For example, one common issue with rainwater is with its acidity and copper pipes that are often used to plumb water throughout a house. You have probably seen these copper pipes under your kitchen sink. What only became realised in recent years was that the acidity of rainwater remaining in copper pipes can cause copper to leach into the water. Mains water generally doesn’t have the same problem, since it is already treated and much less acidic. Consumption of high levels of copper can cause nausea, vomiting, diarrhoea, gastric (stomach) complaints and headaches. Long term exposure over many months and years can cause liver damage and death.

Evidently what is thought to be safe today, may not be tomorrow. While you can run your tap for a minute or so to avoid copper particles, and rainwater from a properly maintained tank is generally safe to drink, installing good filtration at taps water will be consumed from seems to me like an intelligent safety measure.

So then, rainwater is safe to drink and obviously very crisp and fresh when it is well kept. Hopefully you found this article helpful and better understand what you need to do if you want to consume rainwater in your tank. If it has, please share it with others, or leave a comment below. I’m happy to also try answer any questions you might have.