electric boiler water heater on the blue wall

Hot Water Services FAQ

difference between storage hot water service and continuous hot water service

There is water dripping from the open pipe on the side of my storage hot water service. What is this pipe and why is this happening?

  • The pipe which you are referring to is the PTR valve, which stands for Pressure Temperature Relief valve.
  • The function of the PTR valve is to relieve excessive water pressure in the tank so that it doesn’t explode.
  • Excessive pressure can build in the tank if the following happens:
    • The mains pressure is too high
    • The water expands excessively when heated.
  • It is normal it to drip slightly when the water in the tank is being heated.
  • If it is dripping all the time, give our local Melbourne plumbers a call and we can come out to change it over.
  • If you have high water pressure, we may recommend that a pressure limiting valve is installed. This will also prolong the life of your hot water service.
  • It is good practice to have the valve changed every 5 years for safety reasons.

How long do hot water services last?

  • On average, most hot water services last around 10 years
  • This varies depending on the application of the hot water service
  • We have seen hot water services last in excess of 20 years!

I am looking for a new hot water service. Which ones should I buy?

  • The two main types of domestic hot water services on the market are storage and continuous.

Storage hot water service

Continuous hot water service

  •  Stores and heats hot water inside the tank all day, even if no one uses the hot water

  •  Can be electric or gas

  •  There are units available for inside and outside applications

  •  Use a small amount throughout the day to heat the water

  •  Only turns on when the hot water is turned on, heating the water to the required temperature on demand

  •  Mostly gas in domestic applications as electric instantaneous units typically require 3 phase power

  •  There are units available for inside and outside applications

  •  Use around 5x the energy of a storage system but only when the hot water is being used


  •  These units can be efficient for households that use a moderate amount of hot water

  •  As the energy damage is low, the gas/electrical line running to the unit does not have to be large, which results in lower initial installation costs

  •  Stainless Steel tank models come with excellent warranty periods on the tank

  •  Gas units do not require electricity to run


  •  Compact in size and are wall hung so they can be out of the way

  •  As it only uses energy when the hot water is used, they can be very efficient for those who have low use of hot water, or are not home often

  •  The hot water never runs out!

  •  Some units on the market carry up to 12 years on the heat exchanger (tank version of a continuous hot water unit)


  •  Storage units are large and bulky, making it inconvenient if there is a lack of space

  •  They do all eventually run out of hot water when the tank stored hot water in the tank runs out

  •  As they have a PTR valve, they require periodic maintenance and replacement

  •  Because the water in the tank must be stored above 60 degrees to kill any bacteria units, they may require a tempering valve to reduce the temperature to 50 degrees in accordance to AS3500.2


  •  As the hot water does not run out, energy costs can increase drastically when there is high usage.

  •  Because they use 5x more gas than a storage gas water heater, they require a large gas line

  •  Large gas lines can be expensive especially if the unit is positioned far from the gas meter

  •  They also require a power point within 1.5 meters of the unit which can add to the set-up cost

My hot water in the shower goes hot and cold without me even touching the taps. Why is this so?

  • The most common cause of this issue is the tempering valve.
  • Tempering valves are installed to hot water services and hot water ring main (usually in apartment blocks) to reduce the temperature, before it gets to the shower or faucet. This is so that it complies with AS3500.4 Clause 1.11.2, that hot water delivery shall not exceed 50 degrees, for sanitary fixtures for those who are not young or disabled.
  • Over time, tempering valves can become faulty and the internal mechanism cannot maintain a consistent delivery temperature.
  • They should be checked for proper function annually and replaced when they can no longer hold a steady temperature.

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