Pool Water Chemistry: Troubleshooting Guide

1. Pool Water going Green

There are a few potential causes for pool water turning green, most link to signs of poor water chemistry. Usually, a green colour will indicate either a low disinfectant residual or high cyanuric acid levels.

Key parameters to check: Chlorine, pH and cyanuric acid

Solution:

• Carry out a chlorine and pH test to ensure both of these key parameters are within the ideal range (ideally 7.2-7.4 for pH, free chlorine residual of 1.0 mg/L).
• Check the cyanuric acid levels (recommended level is 25–50 mg/L) and reduce if required by diluting the pool water.

2. Salty Taste in Water

If bathers are reporting a salty taste from the pool water, this is likely due to the TDS levels in the pool being too high.

Key parameters to check: TDS

Solution:

• Check TDS levels using Pool Electrochemical Meter (recommended level is no more than 1000 mg/L higher than that of the mains water, up to a maximum of 3000 mg/L).
• Reduce TDS levels in the pool using dilution if required.

3. Cloudy Water

Highly turbid water usually indicates an imbalance in pool chemistry parameters, specifically linked to a lack of disinfection control. High combined chlorine values can cause a reduction in water clarity, this could be caused by any of the parameters which affect water balance. Inefficient coagulation and flocculation processes, or inadequate filtration can also cause highly turbid water.

Key parameters to check: Turbidity, water balance

Solution:

• Check the turbidity of the pool water (usually recommended that the turbidity level in a pool should be no more than 0.5 NTU).
• Carry out a water balance test to ensure effective disinfection and adjust parameter levels as required.

4. Signs of Erosion of Grout in between Tiles

Potential causes of erosion of grout in the swimming pool include poor water balance, low calcium levels or high sulfate levels.

Key parameters to check: Calcium hardness, sulfate, water balance

Solution:

• Carry out a sulfate test and adjust down to acceptable levels.
• Carry out a full balanced water test and adjust levels accordingly.

5. pH Difficult to Control

If the pH of the swimming pool is difficult to control, this could be pH ‘bounce’ due to low alkalinity levels.

Key parameters to check: Total alkalinity

Solution:

• Carry out a total alkalinity test and adjust to required level (recommendation is between 80–200 mg/L)
• If alkalinity levels are too low, sodium bicarbonate can be added to increase readings.

6. pH Difficult to Adjust

If the pH level of the water does not seem to be changing, even after addition of chemicals, this may be due to pH ‘lock’. This happens when the pool alkalinity is too high.

Key parameters to check: Total alkalinity

Solution:

• Carry out a total alkalinity test and adjust to required level (recommendation is between 80–200 mg/L).
• If alkalinity levels are too high, dilution can be used to reduce the total alkalinity.

7. Complaints of Stinging Eyes and Skin Irritation

Eye and skin irritation is usually caused by either the pH or disinfectant level being outside of the recommended range. If the free chlorine level is too low, or the combined chlorines too high, this can cause irritation and is unpleasant for bathers.

Key parameters to check: pH, chlorine.

Solution:

• Measure pH levels to ensure they are within the recommended range (ideally 7.2-7.4). If the pH is outside of this range, then adjust.
• Measure free, combined, and total chlorine levels. If any of the chlorine values are outside of the recommended range (free chlorine residual of 1.0 mg/L, combined chlorine less than half of the free chlorine and never more than 1 mg/L), then adjust.

8. Problems with Scaling or Corrosion of Pool Fixtures and Fittings

If there is scaling or corrosion on pool fixtures and fittings this is likely due to the water not being in balance.

Key parameters to check: Water balance.

Solution:

• Carry out a full water balance test to identify the issue.
• Adjust the water chemistry parameters as necessary.