Clogging cause – precipitation

What is precipitation? When a reaction causes dissolved salts to combine and become non-soluble.

Another way to look at it is that although you may only be adding liquids (e.g. water, chemicals, and fertilizers) into your drip system, they can interact and create solids that will block your system.

You need to proactively avoid the risk of precipitation in your system.

Below are some common causes of precipitation, and their treatments.

Calcium carbonate precipitation

This is the most common form of precipitation.

Risk factors

  • Water with a pH of 7.5 above and bicarbonate levels (HCO3-) of 2 meq/l (112 ppm or 112 mg/l)



Treatment during the season (when required)

  • Periodic injections of phosphoric acid for 30–60 minutes to maintain pH under 4.0, which can be done as part of the fertilizer regime of phosphorus



Iron and manganese precipitation

This often occurs in groundwater where it is soluble, but oxidizes and precipitates when exposed to atmosphere. This can cause clogging even in low concentrations.
Also, some bacteria use iron and manganese as an energy source and can create filamentous slimes.
If you see reddish stains or rust particles, this is a warning sign. Iron will be reddish, and manganese will be darker (near black).


Risk factors

  • Iron 0.3 ppm or higher

  • Manganese 0.15 ppm or higher



Treatment (iron precipitation)

  • Aeration and settling:
    • This is the best treatment for high concentrations (10 ppm or more) and works best when water
    pH is 6.5–7.5.
    • Pump water into a reservoir to allow the iron to settle out.
    • Additional aeration is recommended.
    • Once settled, the water is safer to use.

  • Create chlorine precipitation and then filter:
    • Inject chlorine into the water source to cause oxidization of the (ferrous Fe+2) iron, which in turn will create precipitates (ferric Fe+3) that can be filtered.
    • Of course, this chlorine injection must occur before primary filtration (media filtration recommended).

  • pH control:
    • Lower the pH to 4.0 or below for 30–60 minutes to dissolve iron precipitates.


Treatment (manganese precipitation)

  • Create chlorine precipitation and then filter:
    • Inject chlorine into the water source to cause oxidization of the manganese (Mn+2), which in turn
    will create precipitates (Mn+3 or +4) that can be filtered (media filtration recommended).
    The precipitation of manganese requires several minutes of contact time prior to filtration.


Acid / chlorine is dangerous and their use should be in compliance with LOCAL safety LAWS/ REGULATIONS. To learn about the health and environmental hazards and the required safety means read the safety data sheets of such materials. Please also refer to the acid handling guidelines and the chlorine handling guidelines.


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