HJ Cooper Stainless Steel Low Pressure Cylinders


Discontinued August 2017

Superseded by the Rinnai Low-Medium Pressure Stainless Steel cylinders.

A fantastic replacement low pressure hot water cylinder, these cylinders cover your needs from low-medium pressure. Connect to a hot water heat pump or solar system using extra eco inlet connection (excl. the 135 L) either now or in the future.

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Product Details

A range of hot water cylinders (135-250 L) that can be used at low and medium pressure. The 250 L cylinder has the option of a second element for faster recovery making it less likely you'll run out of hot water during high demand periods.

The range of hot water cylinders has triple entry making installation easy.

Suitable for

  • indoor installations only
  • low-medium pressure systems
  • residential and commercial applications
  • left or right, or bottom plumbing connections
  • connection to an open loop solar or hot water heat pump system

Not suitable as a pool or spa heater.

Water quality
HJ Cooper water heaters are manufactured to suit most New Zealand council water supplies. However some water supplies can have a detrimental effect on the water heater, its operation and life expectancy.

Water supplies with a high level of calcium carbonate (hard water) can cause scaling on hot surfaces. We recommend a water temperature of no more than 65 °C to minimise scale build-up. Scale reducing or water softening devices should be considered in hard water areas. The unit is not guaranteed against damage due to scaling. 

Technical Specifications

Capacities and element sizes
Capacity Element size
135 L 2 kW
135 L 3 kW
180 L 2 kW
180 L 3 kW
250 L 2 kW
250 L 3 kW

Not required


Hot and cold water connections ¾ " (20 mm)


Inner cylinder- duplex stainless steel
Outer casing - galvanised steel


Incoloy 825 alloy sheath element positioned at the bottom on the tank. Twin element options are available.

Operating pressures

Maximum inlet pressure - 120 kPa
Maximum working pressure - 120 kPa

Pressure testing

To 3 bar

Thermal insulation

CFS-free polyurethane foam compliant with MEPS standard


Robert Shaw 30 A contact thermostat, manually resettable at 85 °C. Thermostat can be upgraded to an auto-reset thermostat for solar and hot water heat pump applications.

TPR valve


Weight empty (approx)
  • 135 L = 29 kg
  • 180 L = 35 kg
  • 250 L = 45 kg
Cylinder recovery times (theoretical)

Based on a thermostat temp. setting of 60 °C and an incoming water temp. of 15 °C

Model 2 kW 3 kW 2 x 2 kW 2 x 3 kW
135 L 3 hrs 32 mins 2 hrs 22 mins - -
180 L 4 hrs 44 mins 3 hrs 9 mins - -
250 L 6 hrs 34 mins 4 hrs 23 mins 3 hrs 17 mins 2 hrs 11 mins

August 2017 and superseded by the Rinnai Low-Medium Pressure Stainless Steel cylinders