What’s inside the cartridge

Each filter contains five layers working in sequence: a coarse screen for sediment and rust, a foam distributor for flow and fine particles, activated carbon combined with an oxidation reduction alloy for chlorine, organics and metals, a mixed bed ion exchange resin that removes the dissolved solids, and a fine screen with a non-woven membrane as a final pass. The ion exchange stage is what separates this from a standard carbon cartridge and what brings the TDS reading close to zero.

When to replace

There is no fixed replacement interval, and this is the single most useful thing to understand about these filters. Life depends on how much water you filter and on the TDS of your incoming tap water. ZeroWater’s guidance puts tap water at 002 to 050 ppm at 40 or more gallons per filter, roughly 150 litres, dropping to around 8 to 15 gallons at 301 to 400 ppm. Norwegian tap water is generally at the soft, low-TDS end, so filters here tend to last considerably longer than the two to four weeks often quoted in markets with harder water.

Use the TDS meter that came with your jug. Replace at 006 ppm or higher. Taste gives you the same warning: a sour or lemon-like note means the resin is reaching capacity and releasing hydrogen ions, and a fishy or ammonia-like note means it is spent. Both are normal end-of-life behaviour rather than a fault, but they do mean the cartridge has stopped doing its job.

For coffee use

If you are using the filtered water as a base for mineral recipes, a drifting TDS reading matters more than it does for drinking water, because your recipe assumes you are starting from zero. Two ppm of unaccounted-for minerals is a small error, but it compounds if you are dosing precisely. Measuring before each batch is worth the ten seconds.

Certification

Certified by IAPMO R&T against NSF/ANSI Standard 42 for chlorine taste and odour reduction, and against NSF/ANSI Standard 53 for reduction of lead, hexavalent chromium, PFOA, PFOS and mercury, at a 15-gallon rated capacity.

Specifications

Storage

Avoid leaving a partly used filter out of the jug for long periods. Keep unused cartridges sealed in their packaging until needed.