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Watertight Plumbing Blog


Be Prepared - Hot Water and Power Cuts

At the home show this year we had a few people asking whether a Rnnai INFINITY® would keep working if the power went out – being on gas.

This is a great question, and the recent earthquakes in the South Island brings the message of being prepared to the front of mind.

In this blog we will talk about 3 things:
  1. Electric and Gas Hot Water Cylinders
  2. Continuous Gas Hot Water Heater (Califont)
  3. What do to with gas following a large earthquake


Many households in NZ will have the standard electric or gas hot water cylinder. This is heating and storing hot water ready for use when required. When the power goes out, the water stored is still hot, and will stay hot for approx 8-12 hours if it's not used. As you use the stored hot water, cold will begin to fill the cylinder, replaces what is being used, and gradually cools everything down.

In a natural disaster scenario, using the stored hot water sparingly will allow you to preserve this a bit longer.

Those of you who happen to have a wetback fireplace however will know that it's no problem as the fire can heat the hot water! Wetback ready cylinders are still available, less common however, and only available as low pressure.


Those with continuous gas hot water know that it's fantastic. The Rinnai INFINITY® VT26 delivers 26L of continuous hot water per minute, delightful. However although they run on gas, the ignition and fan run off power and without it, the unit won't heat.

So when the power goes out, what do you do?

Depending on how your Infinity is installed, if it is plugged into an external power point you can simply plug this into another power source, ie generator/inverter – or your neighbours house!

If that is not an option, there is the ability to have installed an Uninterrupted Power Supply (UPS).

Think of it like a battery backup. It is a small box that is connected to the power of your infinity and as the power is on it is charged. If the power fails, then the UPS will immediately it kick in and starts running of the battery power. These are most commonly used to protect big computer systems/servers so there is no interruption and power can remain on for a limited time.

Depending on the size you get, this can give an Infinity 30 minutes – 1 hour of continuous use. With limited use, your hot water can run for a while.


Following a significant earthquake it's best to isolate your gas and have a gasfitter check over your lines. You'll be on either Natural Gas or LPG.

Natural Gas –
Locate the gas meter box on your property. There will be a handle similar to this picture. This can be turned off – normally a 90deg turn.
LPG Bottles –
Bottles have a round tap on the top, if it is safe to do so turn both bottles all the way off.

If you smell gas following an earthquake, and it is safe to do so, turn off your gas supply. Open any windows and doors to get ventilation and keep out of the area. Don't use your phone to call someone or anything else electrical or anything that could spark/flame in the area – go outside.


Be Safe, Be prepared.


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