Brown or Tea-Coloured Water? Tannin Causes and Fixes

Glass of tea-coloured water with leaves from a rainwater tank

Brown, tea-coloured water with a bitter taste and unpleasant odour is often caused by tannins, which Puretec explains come from water sitting in decaying vegetation and leaves. Tannin is common in river and surface water but can also turn up in rainwater. For low levels in rainwater, Puretec recommends the TR20MP2 tannin cartridge in a multi-stage system; for high levels in river and surface water, its TAN40 resin systems.

What causes tannin and what does it do?

According to Puretec, tannins give water a bitter taste and unpleasant odour, and the tea-coloured water often leaves stains on spas, sinks and toilet bowls. If your staining is orange-brown and you are on bore water, iron may be the cause instead – see our iron staining guide.

Low tannin in rainwater: TR20MP2 cartridge

The Puretec TR20MP2 reduces tannin using selective ion exchange resin. Puretec notes:

it is designed to reduce tannin and organics only, so it is used as part of a two or three-stage system
sediment pre-filtration is recommended to avoid premature blocking, and carbon post-filtration to further reduce taste and odour
it needs to be regenerated before use, and again whenever colour starts to return to the water (see the user guide)
it suits low-level tannin issues in rainwater.

Puretec describes the Hybrid E13 as the ideal system to use with a TR series cartridge, because it provides the sediment pre-filtration and carbon post-filtration required, finishing with Radfire™ UV that kills up to 99.9% of bacteria.

High tannin in river and surface water: TAN40 systems

For high tannin levels and high water volumes, Puretec offers the TAN40 series, which uses Tannimax resin with a selective ion exchange and absorption process:

TAN40-E1 automatically regenerates the resin.
TAN40-E3 has a smart valve with an integrated water meter and automatic capacity calculator, regenerating once capacity is reached.

Puretec says these systems need very little maintenance beyond replenishing salt, with resin lasting approximately 5–6 years. Regeneration frequency depends on tannin levels and water use, and a sediment filter should be installed before the TAN40 to protect the resin. TAN40 systems are designed to order – call us to discuss.

River water: test first

Puretec notes river water contains natural matter, suspended solids, tannins and bacteria, and its composition varies, so it recommends a water test before ordering any product. Its river water solutions are multi-stage packages designed around your usage.

Installation: connection to your water supply must be carried out by a licensed plumber, and any hard-wired electrical work by a licensed electrician.

Frequently asked questions

Can a carbon filter fix brown water?

Puretec uses carbon as a post-filter to further reduce taste and odour, but tannin itself is reduced with selective ion exchange resin, such as the TR20MP2 cartridge or a TAN40 system.

How long does a TR20MP2 cartridge last?

Puretec says the TR series cartridge needs to be regenerated before use and whenever the colour in the water starts to return. How often depends on your tannin levels and water use.