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Valves and controls

Valves and controls are required – particularly in mains pressure systems – to protect water supplies from contamination and to achieve the desired water pressure, flow and temperature.

On this page:

  • Valve requirements
  • Isolating valves

Valve requirements

Valve and control device




Isolating valve

Manually operated valve to isolate one section of the system

At the property boundary for all mains connected installations

Adjacent to tank outlet where there is on-site supply

  • At the entry point to the building
  • At a supply tank
  • At the hot water cylinder
  • Any other fixture where frequent maintenance is required

Pressure limiting valve

Limits the pressure within pre-set range

With mains pressure systems where the water pressure could exceed the pressure rating of the pipe material or hot water cylinder

  • Where mains pressure is very high or fluctuates excessively

Non-return valve

Prevents reverse flow within or from the system

At the hot water cylinder to prevent water from the cylinder from returning to the water main or being delivered from cold water outlets if mains supply fails

  • At the property boundary
  • At any pump

Line strainer

Filters particles of solid matter from the water to protect other valves further downstream

Where other valves could be damaged by solid materials

  • At the entry point to the building
  • At the hot water cylinder on all systems

Pressure reducing valve

Reduces the pressure to a pre-set level

To reduce mains pressure on a low pressure hot water system

  • To provide balanced low pressure cold water to other fixtures on the same system

Expansion control valve (cold water)

Releases pressure in the cold water feed pipe caused by the expansion of water in the storage water heater cylinder during normal operation

On any valve-vented hot water cylinder

  • Retrofitted to all existing valve-vented hot water cylinders (low and mains pressure)

Pressure relief valve (PRV)

Releases pressure in the storage cylinder if it rises above the pre-set limit

On low pressure (<120 kPa) valve-vented hot water systems that do not incorporate an open vent pipe

Temperature/pressure relief valve (TPR)

Operates above a pre-set temperature and pressure

On valve-vented hot water systems >120 kPa

  • All valve-vented systems (low and mains pressure)

Temperature limiting thermostat

Controls the temperature of the water

On the hot water delivery to all personal hygiene fixtures and on wetback installations

On all hot water delivery to personal hygiene fixtures

Isolating valves

Isolating valves are required to be installed in accessible position points in the supply system to allow maintenance and repairs to be carried out. They must be provided in accordance with AS/NZS 3500.1 and NZBC G12/AS1 as shown below:

Isolating valves


AS/NZS 3500.1


At the boundary



Inlet to a storage tank
(cold or hot)



Outlet to storage tank
(over 50 litres)



Inlet to a flushing cistern



Each appliance



Each backflow prevention device



Each thermostatic mixing valve



Each pressure limiting device



At each branch serving a separate dwelling