Author Archives: Hot Water Cylinders NZ

Rinnai is getting greener in 2017

Rinnai have been busy with some exciting changes to products making sure they remain one of New Zealand’s preferred suppliers of electric hot water cylinders. The next 12 months will see some exciting changes to their range starting with changes to some of the Mains Pressure Enamel products.

Always striving to be at the forefront of future-proof technology, Rinnai, as part of our commitment to the environment has made changes to our manufacturing process. Innovations to the materials that we use to assemble our finished products will enable our cylinders to be kinder to the environment while still allowing us to meet the same exacting standards you have come to expect.

These changes will mean that the height of some of our Mains Pressure Enamel Electric cylinders will be changing over the coming months.

The first of these changes will be reflected with the production of our Mains Pressure Enamel 180L 488 product (ME18048830/ME18048820). This means that all orders from now on will be fulfilled with the new height.

The full schedule of changes to affected Mains Pressure Enamel cylinders can be found below:

ME18048830 180 488 1660 1695 3 NOW
ME18048820 180 488 1660 1695 2 NOW
ME25059030 250 590 1580 1595 3 MID NOV 2016
ME25059020 250 590 1580 1595 2 MID NOV 2016
ME250590D30 250 590 1580 1595 2X3 MID NOV 2016
ME250590D20 250 590 1580 1595 2X2 MID NOV 2016
ME18059030 180 590 1190 1205 3 END NOV 2016
ME18059020 180 590 1190 1205 2 END NOV 2016
ME09048830 90 488 955 1030 3 EST MAR 2017
ME09048820 90 488 995 1030 2 EST MAR 2017
ME13548830 135 488 1295 1328 3 EST JAN 2017
ME13548820 135 488 1295 1328 2 EST JAN 2017
ME30059030 300 590 1790 1805 3 JUN 2017
ME30059020 300 590 1790 1805 2 JUN 2017
ME300590D30 300 590 1790 1805 2X2 JUN 2017
ME300590D20 300 590 1790 1805 2X3 JUN 2017

From November 2016 we will be phasing out the dual element 2kW and 3 kW 180L Mains Pressure Enamel products (ME180590D30 and ME180590D20) from our range. Stocks of this product will not be replenished and orders for these products will continue to be fulfilled while stocks last.

As always, Rinnai is committed to the environment and to our customers. For more information on any of the products discussed above please contact us 0800 4 CYLINDERS

Blowing up a hot water cylinder

I made this GIF from an experiment done by Myth Busters to show the extent of damage a hot water cylinder can do when there is no pressure relief. blowing-up-hwc

The image above reinforces the importance of using individuals that understand the physics of hot water and the effects an installation can have on its surroundings.

So at what point will a cylinder explode?

In principal it’s simple to understand. Heating a substance causes molecules to speed up and spread slightly further apart, occupying a larger volume that results in a decrease in density. So “larger volume” means “more space” which is limited to the size of the hot water cylinder.

If hot water is not used and your thermostat fails, your immersion element will continue heating your water (to boiling point) until such time one of the pressure relief valves activates and relieves the pressure. Every installation should include two relief valves, one on the cold water side and one on the hot water side.

This regulation was put in place around 1997 meaning that any cylinders installed prior to that may only have one source of pressure relief. Hence the low pressure vent copper pipe going through the roof.

This is where it gets tricky. Many installers dont bother replacing older valves when replacing an old hot water cylinder with a new one. Others have managed to install a tempering valve on a low pressure system right into the overflow pipe, blocking the only means of pressure relief. The hot water system then becomes a time bomb which may result in something pictured above.

Sometimes its not the plumbers’ fault but rather the homeowner who sees a pipe dripping on the outside of a house and thinks.. “Oh, this should not be leaking” and decides to “blank” it off by any means available, creating the perfect conditions for a catastrophe. My recommendation on this is, see a dripping pipe? Please call the plumber.

If you are unsure about what valves you need or already have, send us an email or give us a call for help.


Gas Water Cylinders and Saftey

dux_hot_water_cylinderThis 1996 Dux Hardie (a james Hardie product) Vitreous Enamel gas hot water cylinder has had several repairs done over the years. Whether it was a failed gas thermocouple, replacing of a down-draft diverter or Piezo ignition device, we always pride ourselves in the ability of troubleshooting by following a simple process of elimination, identifying and fixing gas water heaters.

After a “smell of gas” was noticed, Hot Water Cylinders NZ were called to the scene to investigate and hopefully fix yet another possible fault. After only a few minutes onsite, our installers identified that an overheating issue had caused a “split in the seams” resulting in a drip onto the flame which evaporated, mimicking the smell of gas. This Natural Gas hot water cylinder was naturally redundant!

After a life span of 20 years the owners agreed it was time for a new and more efficient solution.

The first thing I noticed with these image was the quality and safety awareness of the installation itself. Unlike many older gas jobs we come across, no short cuts were taken and no safety measures were avoided which contributed to long life span and safe operation of this appliance on a property that has been purchased and sold over 8 times in the last 20 years.


A quick look on the labels and manual show how important it is for the gas fitter to read and apply manufacturers instructions, these include:

  • For safe operation this water heater must be fitted with…1) Thermostatnatural_gas_cylinder
    2) Over-temperature control
    3) Combination pressure and temperature relief valve

Additional important points include how important it is to get your hot water cylinder serviced, ensuring valves are operating safely giving your hot water cylinder the best chance to provide you with hot water for many years to come.  Relief valves should be checked for adequate performance or replaced at intervals not exceeding 5 years or less in areas where local regulations apply.

With an appliance that includes an open flame (pilot light), safety must be recognized and followed to prevent harm to person and property. For instance, a gas hot water cylinder must be installed on a fire-proof base. The appliance should not be enclosed unless otherwise recommended by the manufacturer and sufficient ventilation has been provided. Operation should never take place with panels or covers removed and anything flammable should not be stored (prevented) in the vicinity of the appliance. It almost sounds like so much can go wrong, which could be true unless the installation company has enough experience to apply a “prevention” mentality which would eliminate all risks by simply following a code of standard.


In this instance the owner of the property decided to switch to a tankless hot water solution. This meant reclaiming of their garage space and all the benefits that come with tankless water heating.

Being able to reuse the existing gas pipe meant savings on the installation. the only thing left was to remove the gas flue and repair the hole left in the roof. After 6 years of history with this appliance, it think deserves a special spot on our blog!

10 Mistakes to avoid when buying a new Hot Water Cylinder

  1. Price Price Price
    Compare the price you have for one brand with another quality brand. Don’t be shy to ask for an alternate brand quote. Look at the differences and select the product that will most likely meet all your expectations now and in the future. This will also filter out those who are ‘partial to one brand’. They will always give you reasons as to why ‘their’ brand is better than the others.10_Mistakes_to_avoid_when_buying_a_new_Hot_Water_Cylinder
  2. Don’t Settle for Less.
    If you have to replace your existing hot water cylinder, make sure you get the most recent technology and quality. Many installers will try to flog off outdated stock and make it look like the deal of a lifetime. You will be surprised what modern specifications you are able to get for the same price without having to compromise on quality or warranty.
  3. Low VS Mains Pressure
    Let’s face it, with today’s technology, the world is going mains pressure. If you are replacing your low pressure cylinder, don’t let anyone tell you that you can’t replace it with a mains, because you have low pressure tapware. You can in fact upgrade to mains pressure and set your mains pressure system to accommodate your low pressure tapware. That way you have already future proofed for your upcoming new and amazing mains pressure tapware.
  4. Future Proofing
    This ties in nicely with point #1. Believe it or not a cylinder that is future proofed for solar, heat pumps and alternative energy will cost you the same as a cylinder that is not. With climate change and the costs of energy on the rise, you want to be ready for the next energy revolution which will involve having a cylinder that is also ready.
  5. Warranty
    Read the fine print! They say you get a 20 year warranty when in fact it’s conditional to a yearly service and expense, this should not be required at all, especially in the first 5 years. Seven to 10 years is a good indication of where a warranty needs to be here in New Zealand. Please note that parts subject to wear and tear are in most cases only covered by a one year warranty.
  6. Power Supply
    The trouble with cheap quotes is that they tend to leave out what They believe ‘you don’t need’ but will in-fact only benefit you in the long run. For example, this is the case with the power supply to your new hot water cylinder. If you are replacing an older hot water cylinder, your power switch will be of the same age and wont comply. If it’s round and in most cases black (Baker Light Power Switch), it must be replaced. These switches are deemed as unsafe (electrical hazard) by the electrical board of New Zealand because they can only support 10 AMPS (just below 2KW) and most cylinders now require 16 AMPS the same goes for the wiring from and to your hot water cylinder and electrical board. The last thing you want is for an older component to cause damage to your new shiny hot water cylinder or home and voiding the warranty in the process.
  7. Compliant Installation And Certification
    No one expects you to be a plumber but it is always good to know a bit more about your installation. Do the research and find out what the minimum requirements are. The best place to start is by looking at the New Zealand Building Code G12 which can be downloaded for free >> G12 HERE. It will only take 15 minutes to get your head around the basics. You will then be able to ask the right questions and the installer will be very careful not to cut any corners. Make sure your installation complies and that you have received a producer statement on completion. This will be very important when you come to sell the property as it becomes part of your LIM report.
  8. Maximise The Size Of Your Storage
    if you have the space, USE IT. The more water you can store the more efficient you become. They all come with 2KW or 3KW elements so you are not ‘using more energy’ you are only heating more water that is stored and ready to be used. The insulation values are the same so minimal heat loss. Considering point #4, another advantage is, should you decide to add an alternative cheaper form of energy later, you will be able to store more water that has been heated efficiently. Because most forms of alternative efficient energy are dependent on having sunlight or the right temperatures, you want to heat as much water as possible during that time and use your storage outside that time. Hence it’s best to store as much hot water as possible. As a small example, the price difference from going from a 180 Litre to a 300 Litre hot water cylinder is about $300.
  9. Licensed Installers
    We cannot voice the importance of this enough. Make sure the installer is registered! Regardless of whether the installation complies or not, the technician must be licensed and registered by the plumbing board of New Zealand. If not and something happens, your insurance will bail. ASK TO SEE THE LICENSE and on completion ask for a producer statement. Selecting an installer that is a Master Plumber will ensure you have someone that is experienced and insured to do the job.
  10. Drain Discharge Size And Location
    Some guys just looooove cutting corners and the discharge pipe is the most likely place. It takes more materials and more time to run the drain to an approved and less annoying position. On most installations, the drain must be 20mm to comply (refer to G12 above). All pressure relief valves from your hot water cylinder discharge water every now and then. This happens as water is heated and expansion takes place. The last thing you want is for a pipe to be sticking out your front door or constantly discharging water onto your footpath. All drains must discharge into an approved point of discharge. What is considered an approved point of discharge? Give us a ring to find out or stay tuned for my next blog.

What are the pro’s and con’s of a tankless water heater?

Rheem_24_tankless_hot_waterIts not a great thing when your hot water cylinder is leaking and has to be replaced. The only real benefit under such circumstances is that you suddenly get an opportunity to look at a more modern and efficient hot water system for your home.

In New Zealand we are certainly spoiled with unlimited access to gas supply, whether it’s natural gas in metropolitan areas or LPG in more rural areas. With this in mind, the circumstance begs the question whether it is worth looking at tankless hot water heating.

Let’s look at some situations, site conditions and costs to evaluate the pro’s and con’s of tankless water heating.


Lets list some of the benefits tankless gas water heating offers.

Here are the top 5

  1. The cost of natural gas per KW (Which gas to select? see below) is on average 8 cents/KWh + $30/monthly fixed line fee, in comparison electricity is on average 28 cents/KWh offering a significant difference and savings. LPG will cost slightly more but has a much higher burning value. Most tankless water heaters are available in LPG and NG
  2. Continuous flow water heaters deliver an endless supply of hot water that will never run out, as they heat water when you need it, for as long as you need it.
  3. They heat on demand, rather than keeping water hot and stored ready for use, they use less gas than traditional storage water heaters, which is good news for the environment and you. Another important point is that when converting to tankless water heating, you are by default converting to mains pressure.
  4. Tankless water heaters mount conveniently to the wall, taking up less space, which is good news if you have a compact home site or apartment or are just short of space. You can finally convert that hot water cylinder cupboard into whatever your heart desires.
  5. Take advantage of condensing technology which makes some of these gas units 90% efficient saving you even more on your power bill.


What are some the disadvantages of tankless gas water heating?

  • The installation cost is approximately 30% – 40% more expensive than your conventional hot water cylinder installation. Unless you are using a Hydro unit, in most cases an external power point is also required which adds on average another $300 + GST to the installation.
  • Most tankless hot water units incorporate an electronic ignition system replying on 240 Volts. Unlike hot water cylinder storage, If you have a power outage, you wont have hot water.
  • Because cold water has to run through a heat exchanger first, it takes time, this time is translated into a flow rate. Flow rates on Continuous flow water heaters will always be lower than on hot water cylinders which means if you are already on mains pressure, you may notice a drop in pressure. To compensate for this pressure drop, you may have upgrade to the next size Continuous flow water heater. Sizing values are given in Liters per minute for example the Rheem VT 26  will supply 26 Liters per minute.
  • You must always ensure the water heater size you are buying is suitable for your home. If the unit is undersized, you may not achieve the temperatures and pressure you are used to or expect. Continuous flow water heaters are sized by total plumbing points and occupants. for more information please speak to our sales team.


Liquid Petroleum Gas (LPG): Is ideal when you dont have access to natural gas or the getting a supply of natural gas is expensive. LPG has a heating value of 102 (MJ/m3), so much more grunt than natural gas achieving high temperatures with less effort using less gas.

How much LPG gas will you need? A 45 KG LPG Bottle will on average evolve 21 m3 of gas at a cost of circa $90 per bottle. A tankless heater of 26L/ minute will use 200MJ, therefore you multiply the heat value by the amount of energy stored (21m3 stored per bottle x 102 = 2142MJ heat available ) The total is then divided by the demand, 2142 ÷ 200MJ = 10.71 hours. Thats 10.71 hours of showering on one bottle, or 64 x 10 minute showers. Great heating value giving you a long supply of gas.

Natural Gas (NG): If you already have NG on your property, no installation line fess will apply and tankless water heating would be very desirable. Natural gas has a heating value of 40 (MJ/m3) meaning you will use more to achieve a desirable heat. This something to consider when comparing costs with LPG. If available on your street and the cost to get a permanent gas line with meter onto the property is free or at low cost, then this option would be an advantage as there is no handling of bottles onsite and you cannot run out.

Our technicians have developed further methods to save you even more on gas by using smart controllers and specialist appliance commissioning processes.

With variations of readily available gases in New Zealand, tankless hot water heating has certainly become the way of the future. Technology and efficiency is improving daily making this a desirable option for kiwi homes. Maybe It’s time you joined the gas revolution!

Hot Water Cylinders NZ are currently running a special to convert to a mains pressure tankless hot water heater for only $2800! Checkout our special deal here. Questions? Give us a quick call.


Do I need a hot water cylinder tray?

Whether you are getting a new hot water cylinder installed or replacing an existing one, in New Zealand the building code NZBC G12 stipulates that a safe tray must only be installed if water damage can be caused to another household making it an optional item (not a legal requirement which can be declined) for single title New Zealand homes. In comparison, in Australia this is mandatory in all cases.

We fully agree that an installation of a safe tray (also called drip tray) is good practice and should be installed under every hot water cylinder for obvious reasons. The most common reason for these not being installed on most jobs is the rejection of additional cost. In many cases between $ 250 – $750 over and above the hot water cylinder installation because a dedicated 40 mm drain pipe from the supplied tray to an approved point if discharge needs to be installed. Whether this is convenient or even possible in many cases is another question all together.



We from Hot Water Cylinders Ltd recommend that a cylinder tray is installed on every installation, to prevent damage to property and maintain safety. Of course this extra cost is a nuisance, especially when you are spending an additional several thousand dollars to replace your current leaking hot water cylinder!

According to NZBC as a home owner you can decline the installation of a cylinder tray but please consider the following experience:

We have recently been involved in a case where a manufacturing fault has caused damage to property. In this instance the cylinder element seal was damaged and water leaked onto carpets and through the ceiling.  The home owner naturally sought compensation from the manufacturer but the manufacturer referred to their instruction manual which states the following:

All cylinders have the potential to leak water. To minimise damage to other areas of your home, ensure that your cylinder has been installed with a drip tray—the person doing the installation is responsible for this.

Drip tray/catch pan (MUST be fitted)
The warranty does not cover any consequential loss from leaks to the cylinder, so it’s important a suitably drained drip tray/catch pan is fitted.

Consequential losses
All cylinders are required to be installed with a drip tray, this is a mandatory requirement of the installation. If damage is caused by a leaking cylinder that has not been installed with a drip tray the owner can seek compensation through the installer or consider claiming on insurance.

Does this in return put the responsibility with the installer or home owner insurance??

Depending on circumstances and negligence, here are two possible scenarios that could take place, most likely in court.

  1. The Consumer guarantees Act states “You cannot contract out of the Consumer Guarantees Act when you sell goods or services to a consumer.” This means..
    > exclude or try to limit your liability under the Act in fine print
    > tell consumers to contact a third party when they have chosen to seek a remedy from you. Contracting out of the Consumer Guarantees Act means having a written agreement (or clearly stating) that the goods or services you sell are not covered by the Act.This would mean that regardless, the liability in such a case remains with the manufacturer if damage was caused by a manufacturing fault.
  2. The New Zealand building code Clause 6.11.1 of G12/AS1 states “Water heaters shall be installed in accordance with the manufacturer’s instructions” Which in this case recommended the installation of a hot water cylinder tray.

I do have a personal opinion about the above which I wont share and will only say that these two points contradict considerably and would most likely end up in a court of law if no reasonable resolution is found.

In our experience above, thankfully the damage was minor and the manufacturer agreed to cover the costs of the damage despite the wording in the installation manual which in the end was a great outcome.

The moral of the story folks is that, the best means of protection is prevention! Especially if your cylinder is being installed in a location where a leak may potentially cause damage. Hot Water Cylinders Ltd offer the best price guarantee, so why not ask for an optional quote to include this minor extra which can save you lots of hassles in future.

What is a hot water cylinder coil or heat exchanger?


What is a heat exchanger

The simple answer is, a coil or heat exchanger is a device that allows the transfer of heat between two fluids without having them come in contact with each other.

A standard immersion element is by default integrated into the average solar ready cylinder and is considered the primary heat source. When an external secondary heat sources such as solar, heat pumps or even gas boiler are used, most hot water cylinders will not have a heat exchanger to accommodate and potable water is heated directly within the tank.

Systems of this type (without a heat exchanger) are sometimes called “direct systems”, they can be a problem for a number of reasons:

  • The mains water may be corrosive
  • The mains water may be mineralised
  • Mains water will almost certainly have oxygen dissolved in it
  • The location where the system is used may suffer from frostscylinder_heat_exchanger

Corrosive water will attack the collector tubes, this process will be accelerated by any release of oxygen from solution in the water (gasses are less soluble in water at high temperatures). Minerals in the water will form deposits inside the collector tubes at high temperatures (in the same way that deposits are formed inside a jug or kettle). these deposits will eventually block your solar tubes, gas heat exchangers, pumps, valves and other system components.

Heat exchangers in closed loop systems are critical to the performance of the system and should be matched with the heat source (gas boiler or solar for example) being used and the flow rate through the circuit so that the heat being gained by the heat source is efficiently transferred to the potable water by the heat exchanger.

The most common type of heat exchanger is the coil heat exchanger this is integral to the storage tank, although sometimes external plate heat exchangers are used.

Here is one example of a double coil hot water cylinder which can be used for a solar system and gas boiler backup.




Christchurch shake affects hot water cylinder manufacturers.

4.3 magnitude earthquake in Christchurch shakes residence and hot water cylinder manufactures!


Yet another earthquake hits Christchurch and like every other earthquake this one leaves frustration and damage in the millions behind. Peter Cocks have been manufacturing hot water cylinders in New Zealand for decades and despite being prepared for the constant “shakes” every now and then, over 100 hot water cylinder got damaged in the quake.

This of course affects distribution throughout New Zealand, especially Auckland being the largest hot water consumer.

Peter Cocks have been recently sold to Rheem so the timing could have not been any worse/better? I suppose this will fully depend on who is looking at it 🙂

If you live in Christchurch and you are getting your hot water cylinder replaced, ensure your seismic restraint is installed correctly. This could save lives and definitely save you money even in the smallest quake. Hot water cylinders LTD have been busy helping Christchurch residence get their hot water cylinders repaired or replaced. If you are affected by the recent quakes give us a ring for immediate assistance.

We look forward to hearing more about Peter Cocks’ new venture with Rheem and will certainly keep you posted on any product advancements and updates. If you currently own a Peter Cocks hot water cylinder and are concerned about any future warranty related claims, dont be. Peter Cocks have already issued a statement guaranteeing the continuation of all warranties through the new purchaser Rheem. Peter Cocks may continue to operate under the current brand name “Peter Cocks” but only time will tell.

Jason Statham thinks Rheem is bullet proof?

I had to giggle when I watched “The One” over the weekend. An action filled story line played on a multi-dimensional level filled with clichés and “classic” acting ability from Jason Statham and Jet Li. Mimicking typical special effects introduced by the Matrix the movie keeps you anticipated right through to the last showdown between Statham and Jet-Li.
Jason_Statham_with_RheemOn a manhunt, half way through the movie, Statham decides to take cover behind a Rheem Hot water cylinder. Now, I dont know about you but knowing what these products are made of, im not sure I would feel safe standing behind one trying to dodge a bullet!

So what model Rheem is this hot water cylinder?

By its height and diameter I would say this Jason_Statham_thinkingcylinder has a minimum capacity of 250L.
Looking closely at the connections at the top one can clearly identify flow and return pipework. In total 4 connections which exclude the pressure relief valve clearly visible on the side. I would categorise this hot water cylinder within the Rheem Premier Solar and Drain-back assortment.


Further down this article you can find a technical view of how the installation setup could look like.

Some obvious Hollywood neglection.

Other than the fact that this cylinder is EMPTY and will not save your life in a fire fight, why is it not connected to look like it? If you look at the top of the tank, you can clearly identify that it’s fully disconnected with a “stubby” for a hot water outlet. Do you think they upgraded to instant gas and the plumber forgot to take it away or did Hollywood reject the plumbers quote (I would hate to know how much they charge stars for plumbing works) to temporarily provide a “working” hot water cylinder which is full of water making the bullet proofing scene more realistic? I will leave the answer to your imagination! I guess you will just have to watch THE ONE.

After writing this article I have decided to take one of these hot water cylinders into the bush and introduce it to my 308 Browning. We will see how bullet proof a hot water cylinder can be. I will be updating you very soon with a video and some results, you never know, one day a Rheem may save your life!



Low pressure after installing mains pressure?

cylinder_blockageHow would you feel if you just had your low pressure hot water cylinder upgraded with a mains pressure to only get the same low pressure you had before? Not happy, right?!

I thought this story was interesting because it tends to happen very often and we from Hot water cylinders ltd end up getting the phone calls to investigate and repair. In this scenario some cylinder guy replaced the hot water cylinder and forgot to remove the transport thread protection, completing the installation with this inserted into the pipe. After the installation was complete this “bung” found its way to the valve blocking any flow of water. the poor home owner was not sure what to think of it for over 4 weeks and put up with the low pressure thinking it may have been normal until he picked up the phone and made the call.. “Uhm.. excuse me.. if I have a mains pressure cylinder should it be dribbling out of my shower head?”  Well.. NO of course not.

Mistakes made by Noobs are fixed by professionals. Want to learn more bout LP cylinders? Click here for information about low pressure hot water cylinders.


  • The non return valve was installed incorrectly (opposite way in reverse)
  • Debris from the installation found its way to the strainer in the tempering valve blocking flow
  • Transport bungs are not removed
  • The incoming diffuser has accidentally been pushed into the tank causing a blockage
  • Pipework is kinked restricting flow
  • Pipework badly brazed restricting flow
  • Pipework badly crimped restricting flow

Not sure what the issue is? Please give us a ring and we will help you get to the bottom of it!