Mains pressure vs Low pressure hot water systems

What exactly is the difference between ‘Low pressure’ and ‘Mains pressure’ hot water systems in a house and how do you tell which you’ve got?

Low Pressure
Many older New Zealand homes were built with low pressure hot water systems. There are a couple of ways checking whether you have a low pressure hot water cylinder.

1). Check if you can see a vent pipe poking out of your roof or over a gully trap.

2). Compare the pressure from your hot and cold taps. If there is a noticeable difference in pressure, there is a high chance your system is low pressure.

3). Physically inspect your hot water cylinder. Mains pressure cylinders generally have large labels stating that they are ‘Mains Pressure’, but low pressure cylinders may not have any identifiable labels.

There are a few common issues with Low Pressure systems.

  • Poor water flow when showering or filling baths

  • Hot water turning cold in the shower when another tap is turned on

  • The valves will require occasional replacement of washers or diaphragms. If you see water coming out of the vent, this may indicate a problem with the valve. 

  • The element may corrode inside the cylinder, resulting in a sudden loss of hot water.

Mains Pressure
A mains pressure hot water cylinder is made of steel and runs at 600-1100 kPa. The cylinder is closed-vented, so you won’t find a vent pipe anywhere. The advantage of mains pressure is that water is delivered to the entire house at the same pressure, so it is less affected by multiple demands on water usage, such as simultaneous showers, running taps, washing machines etc.

Do I need to upgrade to mains pressure?

There is tapware on the market which has been specifically designed for New Zealand’s low pressure systems. Methven and Felton have a large range of products which work effectively on low pressure systems. However, the overall range of tapware available for low pressure systems is still very small compared to what is available for mains pressure systems. There are other benefits of upgrading to mains pressure in addition to the huge range of tapware that you will be able to choose from. Due to better technology and more sophisticated manufacturing processes new mains pressure cylinders are much more efficient at heating water, saving energy and ultimately saving you money on your electricity bill.

Another increasingly popular option is for gas continuous flow hot water heaters. The water is heated as it passes through the unit so you are only heating the water as and when you need it, and you are not paying to heat and hold hot water in a storage cylinder when you are at work, or away for the weekend.

What does it cost to upgrade to mains pressure? 

Typically the cost is between $2000 - $2500 Exc GST. Mains pressure cylinders are steel and cost more than low pressure, and you will also require a new set of valves. The advantage of mains pressure is particularly noticeable in large family homes, where the hot water pressure remains nice and high when multiple taps or showers are being used simultaneously. It also increases the pleasure you’ll get from your morning shower, there’s nothing worse than being dribbled on by low pressure water.

A bathroom renovation is the perfect opportunity to upgrade an old low pressure cylinder and get the enjoyment of a full mains pressure shower in your new bathroom!