Understanding maximum outlet pressure

Understanding maximum outlet pressure

Regular audits by the VBA highlight that plumbers are lacking in knowledge on maximum outlet pressures. 

The Victorian Building Authority (VBA) regularly undertakes risk-based compliance audits on plumbing works throughout Victoria to ensure compliance with relevant regulations under the Plumbing Code of Australia (PCA). In the most recent report, the three top audit failures were identified as a failure to provide the minimum clearance between the highest part of the burner and the range-hood or exhaust fan; appropriately marked toughened safety glass when used as a splashback, and an inability to demonstrate that the maximum outlet pressure did not exceed 500kPa for other outlets not fire-related.

The issue of non-compliance with regard to maximum outlet pressure is a recurring audit failure.

Should outlet pressure exceed 500kPa the risk is damage from water hammer, reduced life of appliances, taps and fittings and excessive noise in the system. Applicable to both hot and cold water systems under AS/NZS 3500.1 Plumbing and drainage Part 1: Water services and AS/NZS 3500.4: Plumbing and drainage Part 4: Heated water services the maximum flow rate from an outlet for showers, basins and sinks must not exceed 9L/min nor should the static pressure from the water authority exceed 500kPa.

“If the static pressure exceeds 500kPa, you will need to install a pressure regulating device,” says VBA director, technical and regulation, Joseph Genco.

“Valves can be installed anywhere in an accessible location on the cold water lined provided this requirement is met. If full mains pressure is required at a point outside the building, install the valve downstream of those points.”

The auditing process is conducted onsite in the presence of the plumber, who will need to bring the necessary tools to carry out the audit if it is large or complex. Should the work fail the audit, a rectification notice is issued. The rectification notice provides 14 days to resolve the issue, where a second audit is undertaken.

The intent of this regulation is to ensure that the flow rate does not exceed 9L/min to improve water efficiency through tapware. To meet these objectives, the tapware manufacturer is required to supply WELS compliant products. The scheme does not apply to taps or outlets over a bath, however it is applicable to showers, tap equipment, toilets, urinals, washing machines and dishwashers. In most cases, showerheads and taps rated at three stars or more will comply. However, for low or unequal flow rates it may be necessary to use zero star rated products to achieve the required flow rates.

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