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28th May 2020

Cloudy  Swimming Pool Water

Cloudy swimming pool water is due to a number of factors which include the following:-

  1. High total alkalinity or pH which bring hardness salts out of solution.
  2. Low free chlorine allowing a build-up of bacteria to happen.
  3. Poor filtration which is ineffective at removing particles suspended in the water.
  4. The start of an algae bloom.

The use of a test kit or test strips helps to establish what the most likely cause is

Products you will need:

pH & Alkalinity Reducer – To correct high pH and/or alkalinity

Shock Chlorine – To shock chlorinate the pool

Coagulant – To clarify the pool water after killing the algae

Action to be taken if due to high pH and/or alkalinity:

  • The pH tells us whether the water is acid or alkaline and requires checking on a regular basis.
  • It should be maintained in the range 7.2 – 7.6.
  • If the pH is above 7.6, lower it by dosing pH & Alkalinity Reducer at a rate of 500g per 50m3 (11,000 gallons).
  • With the circulation running, distribute around the pool, avoiding the skimmers.
  • Do not dose it in one spot otherwise some alkalinity may be destroyed.
  • Alkalinity should be kept between 80 – 150mg/l (ppm).
  • If necessary, it can also be reduced using pH & Alkalinity Reducer.

Action to be taken  if due to Low free chlorine:

  • The free chlorine residual should be maintained within the ranges 2.0 – 4.0mg/l (ppm) for stabilised and 1.0 – 3.0 for unstabilised chlorine products, even when the pool is not in use.
  • If you are using Chlorine Granules, you will need 90g per 50m3 (11,000 gallons) to provide 1mg/l (ppm) and 64g for Shock Granules.
  • Shock chlorinate the pool using shock granules.
  • Add the contents of one entire 450g shock pot to 50m3 (11,000 gallons), or pro-rata* for other pool sizes.
  • This will raise the chlorine level by approximately 7mg/l (ppm). Distribute the required quantity across the deep end of the pool with the pump running. *Approximately 64g per 50m3 (11,000 gallons) will increase the free chlorine by 1mg/l (ppm).

High stabiliser level

  • Stabiliser is essential in an outdoor pool but if you are using either stabilised chlorine granules, Maxi or Mini-Tabs (including multi-functional products), the stabiliser level may well increase depending on the level of water replacement.  The stabiliser level should be between 30-60mg/l, but ideally at the lower end of this range following a water replacement.

If due to poor or inadequate filtration

  • It is good practice to have the quality of the filter media checked every 2 years. The correct depth of media is essential if your water is to remain free from small suspended particles.
  • Ask your dealer to check that there is a good flow of water being taken from the bottom drain of the pool.
  • The filter may be aided in the removal of very fine suspended particles by the use of a coagulant. To keep the water sparkling add a routine dose each week.