Good quality water is essential for propagation. Water quality is measured by the amount of soluble salts and minerals in the water.
Hard water with high bicarbonates or sulfates can also be a problem, clogging mist nozzles.
Soluble salts are measured using electric conductivity meters and should be below 0.75 millisiemens for propagation.
The alkalinity should show a sodium absorption ration of less than 5.
pH should be between 5.5 to 7.0.
Irrigation water may require treatment for quality. Commercial systems include deionization processes that remove unwanted salts by passing water through a pair of filters that remove anions and then cations.
Reverse osmosis uses a semipermeable membrane to remove salts. Fertilizer may then be added to the water as needed.