The 1st filter

A 5 micron pleated paper cartridge (a surface filter)

Used to meet NSF42 (to prevent shadowing - the ability to hide behind a particle)

Traps the larger organic debris

The 2nd Filter

A Carbon (nominal rating of around 5 micron)

Activated carbon is basically a process where the carbon extracts particles from the water that comes in contact with the carbon. This means that if the carbon is coated in slime, it will not work.

Effectiveness (most to least):

  1. removes odor, improves taste
  2. removes chlorine
  3. very effective on herbicides & pesticides
  4. has a minor effect on lead, arsenic, mercury

Unfortunately activated carbon does not help with:

  1. flouride
  2. dissolved rocks (water hardness - see below)
  3. nitrates & nitrites

The 3rd filter

A 1 micron poly cartridge (a density filter)

This is designed to trap fine organic particles to reward you with crystal clear water,

However this filter will not remove staining, such as clay (being sub micron the particles will pass straight through) or plant dies/leaching from leaves and seeds. 

A little about water hardness

This is measured as 'total dissolved solids' (TDS).

The EPA max is 500 mg/L (ppm). A typical river is 200 ppm and rain is 10 ppm. Some ground waters can be as high as 1400 ppm.

Imagine a 3" cube (say a Rubics Cube) sitting inside a cubic meter. That's 500 ppm of dissolved rocks laced in a cubic meter of water.

Water exceeding 80 ppm generally needs softening, to allow soaps to work and to reduce the risk of 'passing stones'.

Make up of 'hardness'

Remove with a water softener:

The water softener is in simple terms a brine tank that exchanges 'soda' (sodium ions) for the chloride and magnesium salts (the TDS)

  1. Calcium Phosphate / Sulfate
  2. Magnezium Phosphate / Sulfate

Remove with reverse osmosis:

The water flow rate is too restrictive - only suitable for a single drinking tap.

  1. Carbonate / Bicarbonate Chloride
  2. Nitrates / Nitrites - need reverse osmosis
  3. Sodium
  4. Potassium
  5. Manganese 
  6. Silica
  7. Flouride
  8. Selenium