Reasons your hot water temperature is fluctuating! – Instant Gas Hot Water Systems Perth

Reasons your hot water temperature is fluctuating! – Instant Gas Hot Water Systems Perth

February 4, 2021

This article is suited for instant gas hot water systems. If you water temperature is fluctuating and you have a instant electric hot water system installed, read here

Similar to our recent blog post in relation to instant electric hot water systems the answer is not always so simple.

With the instant gas hot water systems, the problem generally comes down to incorrect installation by the gas fitter. When a new gas appliance is installed the gas fitter is required to pipe size the current configuration and ensure the gas pressure will be sufficient for the new appliance, in this instance a gas hot water system.

If the new hot water system is installed with the incorrect gas pressure the hws will turn on/off attempting to keep the flames running resulting in the water temperature fluctuating from hot to cold. The new hws may also work for the first few months, even years after installation before the problem becomes more prominent. This also cause damage to the hot water system and voids the manufactures warranty.

Common instant gas hot water systems with insufficient gas supply…

Generally, the higher output of the system “20l or 26l” (litres per minute), the more likely the system is not getting the required gas pressure however the problem can also happen with the 12l or 16l units.

Other possible causes your instant gas hot water system water temperature is fluctuating…

  1. The taps have ceased and cannot be opened completely which is limiting the water flow.
  2. A flow restrictor is installed in the shower head or outlet limiting the water flow.
  3. The hot water system is due to be serviced.


If your water temperature is fluctuating and you suspect the cause could be an insufficient gas supply we recommend your call a licensed gas fitting to attend and test your gas supply ASAP. Call us on 0477 777 301

Other hot water systems which have issues with insufficient gas pressure issues

  • Rinnai Hot Water Systems
  • Rheem Hot Water Systems
  • Bosch Hot Water Systems
  • Wilson Hot Water Systems
  • Stiebel Eltron Hot Water Systems
  • Thermann Hot Water Systems
  • Dux Hot Water Systems



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