Swimming Pool Chemical Testing Frequency

The following recommendations about the frequency of manual pool chemical testing are risk based. This risk is determined according to whether a pool is automatically dosed and the likelihood of a large rapid change in bathing loads.

Last updated: 22 February 2010

Frequency of pool testing

The following recommendations about the frequency of manual pool chemical testing are risk based. This risk is determined according to whether a pool is automatically dosed and the likelihood of a large rapid change in bathing loads. A motel or hotel pool tends to be low risk while learn-to-swim centres for infants are high risk. Spa pools and hydrotherapy pools are all generally high risk.

Evidence has shown that pools that are automatically dosed and frequently tested are more likely to be adjusted according to the bathing load to comply with the chemical criteria. Unfortunately, most manually dosed pools are not frequently tested and studies have shown that these pools are less likely to comply with the chemical criteria. Testing of pool water to determine its disinfection capacity and to adequately protect public health should be carried out in accordance with the following Table.

Recommended swimming pool and spa pool testing frequency

Sampling location

Water samples for chemical testing should be collected immediately prior to testing. Water should be sampled from a depth of at least 450 mm using an inverted plastic (not glass) beaker in a location away from the inlets (returns). Except for ozone testing, a water sampling point closest to the outlets, gutters or wet deck return, should be selected because it represents the quality of the water leaving the pool. The plastic beaker should be rinsed in the pool water, emptied and then the sample taken by plunging the inverted plastic beaker into the pool, inverting and lifting all in the one scooping motion in the direction opposite to the current.

Water samples for testing ozone should be collected as above but in a location representing a point closest to an inlet (return).

Sampling to confirm automatic control dosing should be taken from a sample tap strategically located on the return line as close as possible to the probes and in accordance with any manufacturer's instructions. As the difference between manual pool readings and automatic control measurements will vary, it is the consistency of variation that is paramount. Diverging or converging readings should be investigated.

Testing equipment and testing

Suitable testing equipment must be used to ensure accurate results. All glassware and plastic ware should be thoroughly washed and rinsed after each testing session. The test methodology specified by the manufacturer of the test kit should be strictly followed.

Plastic or Perspex kits known as '4 in 1' or '5 in 1' kits for backyard pools or test strips are not suitable for testing public swimming pools and spa pools. Photometric test kits are the most reliable test kits, and should be used in preference to colorimetric kits. Males with red/green colour blindness must not use colorimetric kits.

Testing should be performed in the shade preferably in a cool, well lit room. Tests of the most volatile chemicals, such as ozone, free chlorine and free bromine should be conducted immediately. If possible, temperature should be measured directly from the pool.

Fresh tablet reagents in unbroken foil should be purchased frequently and stored under optimal conditions specified by the manufacturer. Similarly, fresh liquid reagents should be stored as a minimum in dark, cool conditions until just before use at each test. Out-of-date reagents must be discarded.

Standard of chemical testing equipment

Further Information

Guidelines for Disinfecting Public Swimming Pools and Spa Pools specify the required disinfection concentrations and other chemical parameters for public swimming pools and spa pools operations.

Public Swimming Pool and Spa Pool Code of Practice provides detailed explanations and information on disinfection, pool chemistry, risk assessment and other issues relevant to swimming pool operation.

Both the Guidelines and Code of Practice may be found at the NSW Health swimming pool website