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Frequently Asked Questions (FAQs)

Hydrotherm is always happy to answer any questions regarding the system itself, installation, the STC Assignment & Warranty Process etc. If you have specific questions that are not covered below, please contact us on either:

1300 769 904


Simply put, no. Heat pump technology has been around for over a 100 years in refrigerators and air conditioners. The heat pump water heaters were first introduced over 50 years ago in places such as Southern United States and Italy, where heat pumps are now well recognised and popular.

Air source heat pumps work exactly the same as your fridge or air conditioning unit, but in reverse. Heat pumps transfer heat from ambient air, then into the refrigerant and finally into the water inside the tank. A more detailed explanation is as follows:

  1. A fan draws in the ambient air and pulls it over the evaporator containing the liquid refrigerant.
  2. The energy from the air is absorbed and turns the liquid refrigerant into a gas.
    The gas passes into the compressor where the pressure is increased, generating enough significant energy to heat the water.
  3. The gas then travels through the closed loop in the water tank and transfers the heat.
  4. The gas then travels through the expansion valve where the pressure is reduced and the refrigerant returns to a liquid.
  5. The process begins again.

Unlike solar panels and evacuated tubes, heat pumps don’t rely on direct sunlight. It uses the energy in air to generate heat. All that the system requires is uninterrupted air flow, click here to see the installation manual for positioning requirements.

All heat pumps by law must complete a low temperature operation and performance test to obtain their Watermark Sticker. The Hydrotherm has been tested down to -10°C and will still produce the required volumes of hot water.

Hydrotherm heat pumps are built specifically to withstand Australian conditions. The tank is made from 316L marine grade stainless steel and has a current impressed electronic anode for maximum protection. Hydrotherm systems come with a full 6 year warranty on all aspects of the system. The expected lifespan of Hydrotherm systems are approximately 10-15 years. 

Please see our Servicing page for details regarding servicing Hydrotherm systems. 

The Hydrotherm unit itself does not require any regular maintenance. Every six months the relief valves should be released to ensure that they are releasing properly.

If the Hydrotherm unit is unused for two or more weeks, it is recommended that the PTR valve be released for approximately 10-15 seconds. However the PTR valve does not need to be released on a regular basis.

Hydrotherm systems have a built in memory to retain all the timers and settings. If power is lost due to a power failure or the shoulder tariff, the settings will be saved and no action is necessary. If the system is off for a long period of time, the clock may need to be adjusted but the settings will remain the same. 

The Hydrotherm heat pump heats the water up to 60°C to comply with Government legislation and to meet Legionella requirements.

However if you are experiencing what you to be believe to be lower than expected hot water temperatures, please contact Hydrotherm on 1300 769 904 or at

It is always important to check your water quality, especially if you live in a cul-de-sac and if your appliances such as a kettle often require replacement. Warranty will be void if you are in a hard water area that records any of the below quantities:

  • • In excess of 600ppm of Total Dissolved solids
  • • Chloride levels exceed 250mg/L
  • • 6.0pH or lower


All of these can be controlled to an extent through the installation of a water filter. Please contact your plumber for further guidance on filters and installation.

The Hydrotherm has been tested, with a reading of 49dB. To give this some perspective it is similar to an outside air conditioning unit.

We recommend that all our clients set the in-built timers on their systems for three reasons. Firstly, all heat pumps run more efficiently during the days (when ambient air temperatures are higher) therefore saving more on the electricity bill. Secondly, having the system set on timers during the day will ensure that the system will not disturb anyone. Finally, like any appliance, the less you run your Hydrotherm system the better it is for the overall lifespan. 

Hydrotherm systems have a timer function with up to three timers, making the heating cycle very customisable. Setting timers will also ensure that you get the most out of your solar PV, if you have one installed. If you need any help at all with setting timers, please call us on 1300 769 904. 

Hydrotherm systems are delivered by third party agents. Please see our delivery page for more information regarding the delivery process. 

Click here to go to our online shop to order the unit or phone us on 1300 769 904. Otherwise we may be able to provide you the details of installers who can offer a supply and install price. Contact us at or on 1300 769 904 for more information. 


All heat pumps must be installed by a solar accredited & licensed plumber in compliance with government legislation and Hydrotherm’s warranty terms & conditions. In order to receive the STCs discount upfront, we only allow customer to use our Partner Plumbers. Click here to find a trusted and accredited plumber visit our plumber locator or call us on 1300 769 904.

If customers wish to use a plumber who is not one of our Partner Plumbers, please give us a call on 1300 769 904.

A tempering valve mixes the cold and hot water to 50°C. Every hot water system across Australia must be fitted with a tempering valve in compliance with AS/NZS3500.4, which was introduced in December 2010. This was to protect people from being scolded by water temperature exceeding 60°C.

Every Hydrotherm comes with a Pressure & Temperature Relief Valve (PTR – 700kPa) and Expansion & Control Valve (ECV – 600kPa) as standard. 

The installer is required to provide a high performance tempering valve, pressure limiting valve (500kPa) and isolating valve. The cost of these valves can be between $150 – $250 and are a requirement for warranty compliance.

During the heating cycle the cold water expansion valve and PTR can release between 0-2L of water. This is why the Government have made it a requirement for the PTR and ECV to be drained off to an appropriate drainage point. The release is required because as the water is heated, it expands and the valves release excess cold water to relieve pressure. If the PTR or cold water expansion valve is leaking continuously and not when the unit is heating, then please contact your plumber as one of the valves might be faulty and needs replacing.

During a heating cycle, Hydrotherm heat pumps can produce up to 5L of condensate water. If the condensate water is not disposed properly, the following can occur:

  • • Condensation water will attract termites.
  • • The excess water can damage the house structure as well as cause superficial damage.
  • • Hydrotherm warranties will be null and void.

These reasons are why the Australian government have stipulated for the condensate to be appropriately drained off.  

Hydrotherm Heat Pumps don’t require a backup electric element. The majority of heat pumps in Australia do not have electric elements as they are only required in very cold climates.

If you go away for a short period of time (1 week or more) then you can switch the unit off from the screen by pressing the POWER button once. We do not recommend switching the unit off at the mains. There is very little energy usage when the unit is switched off and it will heat up once a week to ensure legionella control. If the unit is switched off at the mains then there will be no Legionella protection.

Hydrotherm does have defrost protection. The refrigerant is reversed back through the evaporator and closed loop circuit to heat the pipes and melt the frost. This is done automatically when needed.


A tariff is an electricity pricing structure offered by energy retailers. Different tariffs have individual prices per kWh and time of use per day (i.e. the hours per day they physically supply power). Each state in Australia has a different tariff system.  If you have any questions with regards the tariffs in your area then please contact us on 1300 769 904 or call your energy supplier.

Generally there are three different tariffs:

  • • Continuous Tariff: This tariff is what the majority of the household appliances are connected to, such as, lights, tv, fridge etc. This supplies power 24/7 and is the most expensive tariff. Hydrotherms are compatible on this tariff. If you have a Solar PV system, you can only run your Hydrotherm system from the Solar PV system if the Hydrotherm system is connected to this tariff.
  • • Off Peak Tariff: This tariff is just for electric hot water systems. This gives you 8 hours of power a day between 10pm and 6am.  It is not recommended for heat pump to go on this tariff.
  • • Shoulder Tariff: This tariff is designed for hot water systems, pool pumps and other intermittent appliances. This tariff supplies you with a minimum of 18 hours of power a day, occasionally cutting the power between 7am-10am and 5pm to 8am. Hydrotherm recommends this tariff unless your household has high hot water usage. 

Click here to see more information regarding tarrifs.

The easiest way to check what tariff your system is connected to is by looking at a previous power bill. It will indicate different tariffs by breaking up the energy usage in a table which is normally found on the second page. There is also a contact number to phone for changing over the tariff or for further information. It can take up to 6 weeks for the tariff to be changed over, so ensure you contact them at the earliest point possible.

The Hydrotherm is a fixed unit and must be hardwired into a 10 amp circuit. The junction box must be rated for outdoor use and have an isolator switch. All work must be carried out by a qualified electrician. For immediate use the Hydrotherm does come with a 3 point earthed plug, but this is only a short term fix for immediate hot water. Ensure you discuss with your installer, as they do often work closely with electricians.

If the power has tripped at the fuse box, the hot water system circuit will need to be turned on manually (as with any hot water system). The system’s inbuilt safety function will then delay the heating for 3 minutes as a power failure has occurred. As for the settings on the system, the will be stored as there is an inbuilt battery which saves all the settings.

Comparing hot water systems

The main reason to go with a heat pump over solar (on the roof) is due to the payback period. A Hydrotherm heat pump has a payback period of 6-18 months whereas solar will have a buy back period of over 5 years. This is due to:

  1. The initial installation for a solar on the roof is very expensive. This is due to factors such as the cost of reinforcing the roof, several installers, crane hire and more plumbing materials.

  2. The unit requires a large amount of expensive gas or electric boosting during the winter periods and rainy/cloudy summer days.

  3. The higher supply cost of a solar hot water system compared to a heat pump. 

The biggest reason for purchasing a heat pump is the large difference in operating costs. Hydrotherm heat pumps are generally 70-80% more efficient than an electric hot water system which is why they are eligible for government incentives. The current availability of STCs makes the Hydrotherm heat pump very competitive (Click here to see what STCs are) in the Australian hot water system market. This often results in owners having only a 6-18 month payback period and then savings for the next 10-15 years.

There is little difference between the installation of an electric hot water system and a Hydrotherm heat pump. The one factor potential customers should be aware of is location selection (please see the Hydrotherm Manual for specific requirements). In terms of the plumbing itself, the only main difference in the plumbing is the requirement for the condensate line to be drained off. This is a Government legislation. This can cost no more than $100 in materials and labour and there shouldn’t be a significant difference between the prices of the different installations.

In the past, the cost of gas in Australia has been relatively inexpensive, meaning gas hot water systems were cheap to run. However over the past decade the cost of gas has increased and they are not as affordable to run as they previously were. Gas companies also charge a high connection fee which does not apply to heat pumps as almost every household already is connected to the electricity grid. 

Costs & Savings

The Hydrotherm uses approximately 0.8kWh. In comparison, an electric hot water systems use approximately 3.6kW of electricity. Both system heat at almost the same rate. Therefore instead of being charge for 3.6kWh you will only be charged for 0.8kWh, dramatically reducing your bill and energy consumption.

A standard installation cost is described as a ‘like for like’ scenario, where the old unit can be pulled out and the new unit can be put straight into place with all the plumbing and drainage easily accessible. The installation cost of a Hydrotherm should reflect that of an electric installation and should include a full valve kit, Form 4, piping, lagging, labour and it may also include the removal of the old system. This is, however just a guide, please ensure you speak with the plumber and finalise the cost as every install differs. The typical cost for a like for like scenario is typically $500 to $1,200.

The Hydrotherm’s average savings will depend on some key contributors including your current usage, hot water system and tariff (if applicable). The unit will save between 60-80% of your hot water energy usage which can account to hundreds of dollars a year. To find out how much you can potentially save, visit out Savings Calculator here.

STC Assignment & Warranty Process

STCs are Small-Scale Technology Certificate, previously known as REC’s (Renewable Energy Certificates). STCs are based on the energy (MWh) the unit will save over a 15 year life span and are purchased by energy companies. Click here for further information about the Clean Energy Regulator. STCs are effectively a government rebate on heat pumps and solar PV systems. 

As Hydrotherm deals directly with customers, we are able to offer the STCs as an upfront discount off the full system cost as opposed to customers or installers claiming the STCs. The upfront discount amount depends on your postcode and is calculated automatically at time of purchase. 

In order for Hydrotherm to process the STCs on behalf of customers, we require a small amount of documentation. 

Firstly, we require a completed STC Assignment & Warranty form to be completed once the system has been installed. Customers receive an electronic version of the form at time of purchase. 

Secondly, Hydrotherm will require just one proof of installation from the customer. We can can use any of the following:

• Plumbing Certificate of Compliance (Form 4)
• Invoice from the Plumber
• Electrical Certificate of Compliance (CoC)
• Photographs of the installed system 
A condition of sale of your Hydrotherm systems is that the system is to be installed and all STC Assignment & Warranty Documents received within two weeks of delivery of your unit.  If these documents have not been received, you will be charged with the full cost of the STC amount until we have received the appropriate documents to claim the STCs. If you would like to ensure your system is delivered in advance (eg. for a new build) this can be arranged. Please just indicate in the delivery notes of the checkout process the timeframes for delivery (eg. ASAP, one week, two weeks or a specific date etc.).

Yes, you can use your own plumber and still receive the STCs as an upfront discount off the full price of the unit. However please be aware that prior to processing the order, as a minimum you will need to supply the installer full name, phone number and postal address. Hydrotherm always recommend that customers use one of our Partner Plumbers as we can vouch that the installation be completed to a high standard, will meet the warranty specifications and at a fair cost.

Yes, during the checkout process there is an option for customers to complete the STC process themselves.

Hydrotherm does not process any other rebate for customers. However some states may have additional incentives for installing a heat pump. 


An A5 alarm is caused by an oversensitivity in the pressure switch which is a safety precaution for cold climates. To learn how to turn off the A5 alarm, click here. Note that turning off the alarm will not affect the performance of the unit.

First you should test if the system is heating correctly. To do this, release the PTR valve for 10-20 seconds and observe if the expelled water is indeed hot (note that the water is very hot so beware of scalding). If the water is not hot, please contact us.

If the water is indeed hot, the issue is most likely a faulty Tempering valve. Tempering valves mix hot and cold water to ensure your tap water is at a constant temperature as to avoid scalding. Please contact the plumber who installed the system or one of our Partner Plumbers, who can then replace the faulty valve.

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