Key messages

  • Pools affected by flood waters need to be assessed for hazards.
  • Flooded pool water is likely to be contaminated and require treatment.
  • Seek professional advice before emptying flood-affected in-ground swimming pools to avoid damage.

A flood-affected pool is likely to be heavily contaminated. You should first assess any dangerous hazards, such as electrical safety and fencing. Treatment will prevent bacterial growth and stop pests like mosquitoes from breeding in the water.

Draining pool water

The Victorian Building Authority and the Swimming Pool & Spa Association of Victoria (SPASA) recommends that you seek professional advice before emptying in-ground swimming pools. After a flood, the groundwater table is likely to be high, so if a pool is emptied it can lift and become damaged.

Pre-filtration

Flocculation is recommended before filtration to remove debris and other suspended matter, and to prevent your filter from clogging.

Flocculants are chemicals that can be added to water to cause suspended particles to join together and form larger particles (flocs). Flocculated material can be removed with a vacuum or other physical means like skimming.

Filtration

Filtration can be used to remove the remainder of debris in the pool. Filters should be backwashed frequently to maintain their effectiveness.

Filtration and associated backwashing should be conducted before chemical treatment.

Chemical treatment

Private pool owners should follow the manufacturer’s instructions on disinfection. Aquatic facilities, as defined in the Public Health and Wellbeing Regulations 2009, are required to ensure they maintain the following parameters.

Table 1: Chlorinated aquatic facilities

Chemical characteristic

Swimming pool where cyanuric acid is NOT used

Swimming pool where cyanuric acid is used

Spa pool

Free chlorine (mg/L) minimum

1

2

3

Total chlorine (mg/L) maximum

10

10

10

pH

7.2–7.8

7.2–7.8

7.2–7.8

Table 2: Brominated aquatic facilities

Chemical characteristic

Swimming pool

Spa pool

Free bromine (mg/L) minimum

2

6

Total bromine (mg/L) maximum

8

8

pH

7.2–8.0

7.2–8.0

Follow-up samples

Aquatic facilities should collect microbiological samples to ensure their water meets the following parameters:

  • a heterotrophic colony count less than 100 colony forming units per millilitre
  • coliform bacteria is not detected in 100 millilitres
  • Pseudomonas aeruginosa is not detected in 100 millilitres.

Water samples should be tested at a National Association of Testing Authorities (NATA) accredited laboratory to ensure the highest level of accuracy.