In New Zealand, there are 3 types of hot water pressure: mains, unequal low and equal low.
When choosing any new tapware, it is essential to know what type of water pressure your system is running on to get the best results at the water outlet (tap or shower).
Mains Pressure
If you have gas hot water or a high-pressure hot water cylinder you are in the best position as your water pressure when you turn on the tap or mixer will be strong high-pressure for both hot and cold water. If you put your thumb over the hot water tap and turn it on slowly it is unlikely that you’d be able to stop the water flow.
Low-Pressure
If you are on tank water or have a low-pressure hot water cylinder you could have low-pressure or unequal pressure (low-pressure hot and high-pressure cold) at the water outlet depending on how it has been piped up by your plumber. When you turn on the hot tap or mixer, the water pressure will be low from the hot tap and the cold may be the same or have a higher pressure resulting in either equal or unequal low pressure.
Equal Low Pressure
If you have a low-pressure hot water cylinder the high-pressure mains water must pass through a pressure-reducing valve before it enters the cylinder for the water to be heated.
Ideally, after the high-pressure mains water has been reduced, a cold-water pipe is run to the shower, and the main water pipe continues to the hot water cylinder for heating before re-joining the cold at the shower mixer making it easy to get the right temperature mix. This is called equal low water pressure.
Unequal Low Pressure
If the cold-water pipe is run to the water outlet without being reduced in pressure, when it meets the reduced pressure hot water from the cylinder it will be difficult to mix the two and you will need far more hot water than cold to get the right temperature. This is called unequal low water pressure.
The Water-Pressure-Tapware Relationship
It is important to know what type of system is running in your home when purchasing tap mixers because the connections from the mixer tap to the supply pipe can differ in size affecting the final flow from the tap head.
In addition, shower heads are often supplied with restrictors to control the maximum number of litres per minute through the head. Again, these are all different and can be changed to suit different situations. The restrictor is usually found in the base of a standard shower head where the hose connects.
The manufacturer may supply other restrictors in the same box and it’s always good to check the manufacturer’s instructions for installation of the right one, but if it's maximum flow you’re after they can be removed altogether. People on tank water may wish to keep the restrictors in place as a water-saving device.
If you’re looking to upgrade your bathroom or kitchen tapware, you may be left disappointed and limited in your choices if you have a low-pressure system and any new tapware may not always work correctly with low-pressure systems.
What’s the deal with All-Pressure Tapware?
Tapware that is suitable for unequal pressure is often described as ‘All-Pressure’ and allows your plumber to make small adjustments so that the mixer can be used on mins or unequal pressure systems.
It is advisable that you check your hot water system before investing in new fixtures. At Bathroom Genie we can advise you on the best way to maximise the pressure you have or we can install an economic system that provides a good result giving you confidence with your chosen tapware and shower mixers.
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