Chlorine problems

red eye

- problems associated with Chlorine levels are not difficult to pin down

Chlorine has been added, but there is no reading on the test kit

Possible cause 1 -

  • Old, inaccurate or ineffective test kit

Cure: - Buy a new kit, or test-strips, or change the batteries in your Photometric Meter every year - they are all inexpensive and accurate testing is key to understanding what is happening in your pool 

Possible cause 2 - 

  • The Chlorine level may be so high that it bleaches the colour in the test kit, or exceeds the range of a  Photometric Meter   (although both of these are unlikely)

To check this diagnosis see if you can smell Chlorine at the surface of the water, or repeat the test with only a droplet of pool water, diluted with tap water, in the test tube and watch closely to see if there is a discolouration before the bleaching occurs

Cure: -

  • Determine the level of Chlorine by diluting the sample of pool water with an equal quantity of natural or distilled water; multiply the answer by 2
  • If there is still no reading, dilute the water sample with 3 parts of water; then multiply the answer by 4, and so on
  • Alternatively you can have a sample of your pool-water tested at most pharmacies and pool-shops
  • If the actual Chlorine reading is under 10ppm, suspend dosing until it drops over time
  • If the Chlorine reading is higher than 10 ppm, reduce the free Chlorine by adding Sodium Thiosulphate
  • WARNING: dose Sodium Thiosulphate at 250g per 50 cubic meters
  • Apply in several small additions and test Chlorine levels after each dose
  • Overdosing with Sodium Thiosulphate could leave you with a Chlorine deficit for weeks

Chlorine level is difficult to maintain

Possible cause 1 -

  • The free Chlorine is being decomposed by UV from the sun’s rays

Cure: -

  • If you are using Sodium Hypochlorite or Calcium Hypochlorite, add Cyanuric Acid (stabilizer) at a rate of 500 grams per 50 m³ or 1 pound per 13,000 US Gallons
  • This should be dosed directly into the pool
  • Alternatively, change to a stabilized Chlorine donor such as Trichloro

2nd possibility -

High water temperature

Cure: -

  • Keep a close eye on Chlorine levels in hot weather
  • Once the water temperature goes above 26 °C, the Chlorine demand will roughly double for every 5 °C
  • Increase the dose rate of Chlorine proportionately as the temperature rises

3rd possibility -

  • A build-up of pollutants due to low Chlorine, causing an increased Chlorine demand

Cure: -

  • Superchlorinate to 10ppm to oxidize bather waste and to react out chloramines

4th possibility -

Cure: -

  • TA is a measure of the bicarbonates that are dissolved in the water
  • TA is important because if it’s to low you will experience ‘pH Bounce’ and if it’s too high you’ll have great difficulty in changing the pH value
  • Take a sample of your pool water to your local pool-shop or pharmacy (some Photometric Testers do test for TA)
  • They will test the water and tell you the TA level of your pool water
  • Increase TA by adding dissolved Sodium Bicarbonate with the pump on
  • Reduce TA by adding dissolved dry acid to the deepest part of the pool with the pump off
  • Check the container instruction for quantities

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Ken Walker - MyPoolGuru©