Water

Water use, sustainability, and efficiency by choosing quality systems and materials, and providing environmentally friendly solutions.

Hot water pipes

Hot water pipes must be appropriate for the temperature and pressure of water being piped.

On this page:

  • materials
  • pressure rating of thermoplastic pipes
  • de-rating (rate of loss of strength) factors of some commonly used pipe material

Also see pipe materials, pipe installation, and valves and controls.

Materials

Hot water pipes must be able to withstand the maximum temperature of the water being piped. Pipe material may be copper or an appropriate thermoplastic material.

Materials suitable for hot water supply pipes include:

  • copper
  • polybutylene (PB)
  • chlorinated polyvinylchloride (CPVC or PVCc)
  • random polypropylene (PP-R)
  • cross-linked polyethylene (PEX).

Thermoplastic piping should not be used where a hot water system includes an uncontrolled heat source such as a wetback or a solar heating system.

Acceptable Solution G12/AS1 and AS/NZS 3500.4 require the first metre of length of pipe from water heaters to be in copper.

Grades of PEX vary, and few grades will tolerate 100C water for any significant length of time.

Pressure rating of thermoplastic pipes

Pipes are classified according to their pressure rating (PN) at 20C. For example, a pipe rated PN16 is rated for a pressure of 160 MPa at 20C. Thermoplastic pipes lose strength and ability to withstand the pressure with increasing temperature, and this differs with different materials.

De-rating (rate of loss of strength) factors of some commonly used pipe materials

Temp
(C)

Poly-
butylene

Polyvinyl-chloride

Chlorinated polyvinyl-chloride

Poly-
ethylene

Cross-
linked poly-
ethylene

20

1.0

1.0

1.0

1.0

1.0

27

1.0

0.9

1.0

0.9

0.7

38

0.9

0.6

0.8

0.8

0.8

49

0.8

0.4

0.7

0.7

0.8

60

0.7

0.2

0.5

0.4

0.7

71

0.6

*

0.4

*

0.7

82

0.6

0.4

0.6

93

0.4

0.2

0.5

104

*


*

*

 

* Not resistant to long-term service beyond this temperature.