Why Your Water Tank Is Turning Brown — And How to Fix It Before Damage Sets In

Brown or dirty tank water is most often caused by tannins—the natural compounds released when rainwater mixes with decaying leaves, pollen, and vegetation. On Waiheke, this becomes particularly problematic during pōhutukawa flowering season, when the stunning red stamens shed heavily across rooftops.

As beautiful as they are, they are one of the biggest culprits behind tea-coloured water, bitter tastes, unpleasant odours, and staining on spas, sinks, and toilets.

Left untreated, tannin-rich water can cause residual damage to washing machines, clogging internal parts and leaving clothes less clean with every wash. Potentially, it’s the kind of slow, hidden deterioration that can lead to costly repairs—and it’s certainly not something you want your family or summer guests to experience.

Your trusted solutions: 

Option 1: Book a Tank Clean & Drain with a 10,000L water refill. 

Often with tannin polluted tanks the dirty water is too hard to treat. Instead we vacuum sludge & residue from the bottom of your tank, draining all the bad water then deliver 10,000 litres of water to give you a fresh start.

Option 2: Install a Tannin Reduction Cartridge beside your sediment filter.

The Purtec TR20MP2 Tannin Reduction Cartridge is designed specifically to remove tannins from your water. It works using a special ion-exchange resin that pulls out the tea-coloured stains and improves taste and smell. Because it targets tannins only, it’s best installed as part of a two or three-stage filtration system. This means:

Sediment filter first — to remove dirt and debris so the tannin cartridge doesn’t clog early.

Tannin cartridge next — to remove the colour.

Carbon filter last — to polish the water and reduce any remaining taste or odour.

Call our local Tankman experts today to assess your system and advise which option will work best for your Waiheke home.

Our local Tankman experts can assess your system and advise which option will work best for your Waiheke home. Depending on the quality of your tank water a combination may be needed to restore clean, safe, clear water.