Low Pressure Hot Water Cylinder Supply & Installation Auckland

Low pressure hot water cylinders were developed earlier than a mains hot water cylinder, and are extremely common in New Zealand; they tend to be smaller and are generally older. Low pressure cylinders provide water pressure between 10-15 kPA so its quite common to wait a longer time before hot water will start coming out of the tap or shower.

low pressure hot water cylinder from rinnai

What’s included in our service?

Our team has over 20 years of experience in supplying and installing low pressure hot water cylinders.

Our service includes:

  • Supplying the most appropriate low pressure hot water cylinder for your property.
  • Installing & configuring low pressure hot water cylinders.

As the majority of homes in New Zealand were originally built with a low pressure hot water system, many people look for a replacement to a more modern, high performing system. At Sumich, we have a team ready to give you advice on this and offer the best service.

Why invest into a low pressure hot water cylinder?

Low Costs

  • Low pressure hot water cylinders are generally less expensive to purchase and are cheaper to install and maintain.

Equal Pressure

  • Operating at low pressure deliver water at a reduced flow rate, making them ideal for smaller homes with a lesser need for hot water.


  • Low pressure hot water cylinders are quiet and can be connected to a wetback system.

Low Pressure Hot Water Cylinder Installation

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There are two main types of low pressure hot water cylinder tanks

  • A low pressure, open-vented, header tank system
  • A low pressure, pressure-reducing valve system.

These systems are assembled from copper with a galvanised outer casing and are easily distinguished by the copper pipe protruding through the roof of a house. 

Advantages of low pressure open vented hot water system:

  • The relatively low cost of installation
  • Few valves are required; and it is an equal pressure system
  • It also operates quietly and can be connected to a wet back system

Disadvantages of low pressure hot water system:

  • The large diameter pipework required
  • It requires grading to avoid air locking
  • Hot water is supplied at low pressure
  • Can be prone to pressure fluctuations

Low pressure-reducing valve system

This works in the same way as the header tank system, but uses a pressure reducing valve to reduce the high pressure water from the mains supply down to a pressure, or head, that is able to be maintained within the height of the vent pipe, which usually discharges above the roof.

This system supplies low pressure hot water and high pressure cold water to fixtures, it is commonly known as an unequal pressure system. 

Advantages of low pressure valve hot water system:

  • The relatively low cost of installation and maintenance
  • Few valves are required; and can be connected to a wet back system if open vented.

Disadvantages of low pressure valve hot water system:

  • The large diameter pipework required for hot water supply pipes
  • Low hot water supply pressure; and this system is also prone to pressure fluctuation.
  • A major disadvantage of this system is how difficult it can be to achieve a balanced flow to a shower. 

Mains pressure vs Low pressure hot water cylinders

Mains pressure water heater systems deliver hot water to all outlets at mains pressure; this means that both the hot and cold water is delivered at the same pressure. As this system does not require cold water storage header tanks or vent pipes, it allows for more flexibility in locating the cylinder. 

A lot of older homes in New Zealand will have low pressure hot water systems and there are some ways to check if this applies to your home. If there is a noticeable difference in the water pressure between your hot and cold taps, with the cold tap having a much higher pressure, you most likely have a low pressure system.

You can also check your cylinder for labels; a low pressure cylinder may not necessarily have a label but, mains pressure cylinders generally have a large label. If you can see a vent pipe sticking out of your roof or over a gully trap, this also means you have a low pressure water cylinder as main pressure systems are close-vented and do not required a vent pipe. 

Frequently Asked Questions

A heat pump hot water cylinder is a form of hot water storage tank used in combination with a heat pump system. The cylinder is normally constructed of stainless steel and is insulated to maintain the temperature of the hot water.

In order to heat the water held in the cylinder, the heat pump system extracts heat from the surrounding air or ground. Pipes and valves are then used to distribute the hot water around the house.

The system’s storage component, the heat pump hot water cylinder, ensures that the heat pump runs effectively and consistently supplies the residence with hot water.

Heat pump water heaters use a similar technology to heat up water as heat pumps do to heat rooms. They use electrical energy and a refrigerant to extract energy from outdoor heat to heat the room, the water is then stored in an insulated hot water tank.

  • A large proportion of single lever tapware in the current market requires mains pressure
  • Water is delivered to the whole house at the same pressure so the system can cope much better with multiple hot water demands
  • It also reduces the temperature variations in showers. This is an inherent issue with most low pressure systems. 

While Low pressure hot cylinders become more unpopular as they compete with other water heating systems, such as mains pressure hot water cylinders, heat pump hot water heaters or gas continuous flow water heaters, there is still use for them and continue to be supplied and installed.

A few examples of instance where they are preferred are in older homes, rental properties, secondary farm properties or commercial businesses where hot water use is much lower. The cost of installing these systems or replacing an old one with a “like-for-like” model ranges between $2,000 and $3,000. 

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