5 reasons to switch to mains

1 September 2016
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5 reasons to switch to mains pressure

If you’re ‘scheduling’ your shower when someone isn’t using the kitchen tap to avoid an unwelcome blast of cold water, it’s likely your hot water supply is either low or unequal pressure (where the hot and cold taps are not of equal pressure). 

Most New Zealand homes have an electric hot water cylinder and the ‘traditional’ New Zealand electric hot water system is what is known as ‘low pressure’.  Low pressure or unequal pressure is when the hot water pressure is lower than the mains cold water pressure or between 10-50kPa.  Mains and Medium pressure are the other options.  Medium pressure is where the hot water cylinder can be used at up to 120kPa.  Mains pressure delivers up to 500kPa and provides water pressure that is about 6 times stronger than a low or unequal pressure alternative. 

Most new homes are built with mains water pressure for hot and cold water, a large number of homes over 20 years of age have their hot water supplied using a low pressure hot water. 

How do I tell whether I have a low pressure system?

The easiest way for you to determine if you have Low or unequal water pressure in your home is to look at the hot water cylinder.  If it’s not clearly marked ‘mains pressure’ on the side of your cylinder, then there are a few other ways to tell.  

Firstly, if your cylinder is older than 20 years its most likely low pressure.  If you have a very weak shower or significantly lower pressure at the hot taps compared to the cold, again, you probably have a low pressure cylinder.  If you have a header tank in your roof cavity or a valve vent coming out the top of your roof, you have low pressure. 

If you have hot powerful water blasting out of your shower, then you have mains pressure.

So why should I switch to mains pressure?

Today’s modern systems deliver much better performance.  Here are five reasons for considering the change to a Mains Pressure Hot Water system:

  1. Quick delivery of high pressure hot water.  Once installed the flow of hot water will be similar to that of cold water; no longer the trickle that you may be currently experiencing. This means you can have multiple taps and showers running hot water simultaneously without a noticeable difference in flow.
  2. Larger volumes of hot water.  Older hot water cylinders tend to hold a smaller volume of hot water and are low pressure whereas modern hot water cylinders are high/mains pressure and most common sizes are 180 litres or larger.
  3. Compatibility with modern mixers and taps.  If you are looking to upgrade your home with modern or imported tapware, you may be left disappointed with your investment as low pressure systems won’t provide the best showering experience with unequal pressure.
  4. Longer Warranty periods.  Compared to Low pressure, Rinnai Mains pressure hot water cylinders are backed by a 20 year limited liability warranty (for Stainless Steel models) compared to just 5 years for a low pressure copper tank.

Can I upgrade my home from low to mains pressure?

Yes, and in most cases this is straightforward especially if it's a simple replacement of the existing hot water cylinder and valves for an equivalent mains pressure alternative. In some cases, you will also need to upgrade your tapware.

Now is the time to change

So if you are considering a major renovation to your home, it’s a good time to consider moving to a mains pressure hot water system and enjoy the benefits of a strong, consistent flow of hot showers and avoid any nasty changes in temperature when someone else turns on the hot tap elsewhere in the house.  

You can discuss your options with your plumber or for more information click here


Beth Stemp • 31 months ago

Hi, we are on tank water, can we still have 'mains pressure?

Hiraka Pineaha • 40 months ago

I have a rinai hd 250 ng and can I convvert it to an LPG Thanks


Hi Hiraka,

Yes, our Rinnai HD250 can be converted by a certified gas fitter, they can purchase a conversion kit via their plumbing merchant, it should take around 2 hours of labour to complete.

Otherwise, if you are in Auckland, our in-house service team can do this job for you, you would just need to bring the unit out to our premises at 105 Pavillion Drive, Airport Oaks, Auckland.

Rinnai NZ

Nancy HIggins • 20 months ago

What water pressure flow is needed for 'instant hot water'? I am in a rural area with a water tank.


Thanks Nancy, great question. Our Infinity hot water system which provides instant hot water does require a nominal water flow, so if you are using a gravitational water flow system (without a water pump) unfortunately it is unlikely the Infinity would be suitable.

However, if you do have a pump connected to your tank, it is likely that you will be able to supply water to the Infinity system at least at the minimum required water flow rate. Depending on the size of the Infinity unit that you need, the minimum nominal water rate is between 120kPa and 200kPa. Please see this page on our website for the water supply information.

Hope this helps

Rinnai NZ • 22 months ago

Hi Stan

It really depends where you are located in NZ, there are certain areas that have what we term as aggressive water, Coromandel, Kapiti Coast, to name a couple, whereby it is our recommendation that our enamel range is installed. As they have a sacrificial anode in them, which protects the inner tank from water quality issues.


Rinnai NZ • 29 months ago

Yes Terry,

It is most likely that the water pressure will improve slightly, but unless you change the low pressure piping around the house to mains (increasing the flow capability), you are unlikely to get mains pressure water supply.

Rinnai NZ • 29 months ago

Yes Beth, you just need to ensure that your water pump has the capability of delivering water between -120 – 1000 kpa, depending on the size of the water heater that you are planning to install.

Stan • 22 months ago

Are there any general concerns with upgrading from low to mains pressure. We had a quote and the plumber did not recommend mains pressure or stainless steel cylinders - he said there has been alot of problems with them. Can you pse advise, thank you.

Terry Hay • 30 months ago

Can I upgrade to a mains pressure hot water cylinder if I am tank water?
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