Key messages

  • This page describes only the key elements that should be considered in a contract for treatment and servicing of a cooling tower system to manage the risk of Legionella infection.
  • The precise terms and conditions of the contract – including its duration and price, and the conditions under which it may be terminated – will need to be determined by the contracting parties themselves.
  • The information is not intended to replace the need for contracting parties to obtain their own specialist commercial or legal advice.

Disclaimer

This information describes only the key elements that should be considered in a contract for treatment and servicing of a cooling tower system to manage the risk of Legionella infection. The precise terms and conditions of the contract – including its duration and price, and the conditions under which it may be terminated – will need to be determined by the contracting parties themselves. The information is not intended to replace the need for contracting parties to obtain their own specialist commercial or legal advice.

Model service contract – introduction

This specification deals with best-practice management of corrosion and microbiological control for (insert name of company).

The service required will include the supply of chemicals and services for treatment of the cooling tower at (insert address of site). This includes full cleaning of the tower, including disinfection.

The attached plan shows the cooling tower systems covered by the contract and the piping layout for the system.

Model service contract – scope of work

The contractor shall supply all necessary chemicals and provide all necessary technical services to:

  • maintain the cooling tower in accordance with the attached maintenance schedule
  • ensure that our staff, contractors and the public are not affected by water treatment maintenance or the operation of the cooling tower
  • meet all occupational health and safety obligations
  • note and report any mechanical faults associated with the cooling tower to the contract manager.

Model service contract – quarterly meetings

The contractor shall attend a meeting each quarter with the contract manager to:

  • review compliance with Australian Standards AS/NZS 3666, AS 2031, AS 4276.3.1 and AS/NZS 3896, and legislation (including the Public Health and Wellbeing Regulations 2009)
  • discuss the performance of the cooling tower and the contractor, including any works program that may be required.

Model service contract – indicators

The contractor shall ensure that:

  • the heterotrophic colony count complies with the Public Health and Wellbeing Regulations 2009 in at least 95% of tests over a 12-month period, and that Legionella is not detected in any samples
  • corrosion is at low levels – no visible signs of corrosion should be present (111)
  • chemical control is maintained in accordance with an agreement to be reached before the commencement of the contract. The ranges in the table below are provided for guidance.

Indicative water quality target ranges

Bacteria

Legionella

Not detected (<10 cfu/ml)="">

Heterotrophic colony count

Less than 200,000 CFU/mL

Solids

Total dissolved solids

Less than 1,000 mg/L

Conductivity

Less than 1,500 µS/cm

Suspended solids

Less than 150 mg/L

Calcium hardness

Less than 180 mg/L

pH

pH (for bromine-based compounds)

7–8.5

pH (for chlorine-based compounds

7–7.6

Total alkalinity

80–300 mg/L

Other additives

Biodispersant

Follow the manufacturer’s specifications.

Corrosion inhibitor

Follow the manufacturer’s specifications.

CFU = colony forming units

Where the results of testing do not meet the requirements of the Public Health and Wellbeing Regulations 2009, the contractor must immediately notify the contract manager.

Model service contract – occupational health and safety

The contractor is responsible for the safety of its employees while on-site, in all matters over which the contractor has control. All equipment brought on site by the contractor or its employees must fulfil the requirements of occupational health and safety legislation.

Model service contract – quality assurance

The contractor shall have a formal quality assurance system in place and provide evidence that the quality assurance system has been audited each year.

Model service contract – insurance

The contractor shall have both professional indemnity and public risk insurance in place for the supply of services for the term of this contract. The contractor shall provide an annual confirmation of the continued existence of the policies (112).

Footnotes

111. You may need to seek engineering advice about an acceptable rate of corrosion for your business operation.

112. The level of insurance should address the worst-case scenario where the cooling tower is demonstrated to have been the source of an outbreak of Legionnaires’ disease.