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For many Australians, collecting rainwater from roof tops is the main source for your drinking water. Due to the harsh Australian climate, to help combat the heat that can be generated from the hot summer sun, our houses (water collection points) and water tanks are quite often shaded by native trees and flora. But the trees and foliage that helps protect us from the sun could be poisoning your drinking water!

In the following article, we’ll take a look at what organic plant life can turn your drinking water toxic and provide methods in how you can prevent contamination.

Have you ever seen a tree foaming after or while it is raining?

Eucalyptus bark and leaves contain glycosylated alkaloids or isoprenoids called saponins, which foam when wet. They don’t emerge from the tree but simply wash off the leaves and bark as natural rain/water washes over it. As the water flows down the trunk of the tree, its surface tension is altered, and that can create a foamy appearance just like in the following photo.

If this is occurring naturally as rain/water washes over a tree, then exactly the same ‘filtering’ is occurring when bark, leaves and twigs from Eucalyptus trees are sitting on your roof and water is washing over the debris on its way into your water tanks.

What is saponin? Is It dangerous when consumed?

Saponins, also referred to selectively as triterpene glycosides, are bitter-tasting usually toxic plant-derived organic chemicals that have a foamy quality when agitated in water. They are widely distributed but found particularly in soapwort, a flowering plant, and the soapbark tree.

Saponins can bind cholesterol and thus interfere with cell growth and division. They reduce serum cholesterol by preventing its reabsorption after it has been excreted in the bile. It is hypothesized that the saponins either bind with bile salts or cause the bile salts to bind to the polysaccharides in dietary fiber. Either way the bile salts are unavailable to bind with cholesterol and can make you ill in the long run if you continue to consume saponin without knowing that this can danger your health.

Another chemical bark and leaves contain are Tannins

Tannins are complex chemical substances derived from phenolic acids (sometimes called tannic acid). They are classified as phenolic compounds, which are found in many species of plants, from all climates and all parts of the globe.

We quite often find water tanks discoloured due to tannins from leaves, twigs and bark, which gets into the tank as water runs over the debris sitting on roofs and in gutters. Basically it strains into the water tank (just like infusing a cup of tea).

Aside from discolouration and foul taste of the water, by consuming a large amount of tannic acid can cause side effects such as stomach irritation, nausea, vomiting, and liver damage. Regular consumption of tannin (assuming you still think your water is safe without regular cleaning) seems to be associated with an increased chance of developing nose or throat cancer

(Source: https://www.rxlist.com/tannic_acid/supplements.htm)

Once these chemicals get into your water tanks, we can’t filter it out. If it is too heavily contaminated, we will have to dump the water, sanitise the tank and refill. Therefore, it is best to prevent contamination in the first place with a proper maintenance schedule.

This why we always remind our customers to make it a habit to always check your water tanks. If you leave this organic debris in your tank strainer or gutters, this will only create issues with the quality of your drinking water. Or worse, make you ill.

If you have Eucalyptus trees around your house, make sure to:

  • always check for debris such as leaves, twigs and bark from roofs and gutters
  • clean overflow pipes
  • trim back trees from your water tanks

These are just some simple maintenance tips that can help keep your water Pristine. 💧

Sanitising your water to make it fit for drinking is an absolute necessity. A regular maintenance program, sanitising the tank, and a suitable filtration system will provide you with clean healthy water.

You might think your water is fine, but we can guarantee it could be healthier and better! Pristine water is healthy water, and you deserve the best for you and your family.


In this video you can see the discouloration of water caused by tannins. While the video highlights a water tank full of “wrigglies”, the brown colour of the water is from Eucalyptus trees surrounding the buildings where the water is collected from.

If you have problems with your tank water, contact us for a free quote or tank water assessment