Frequently asked questions about hot water cylinders

1. Why does my hot water cylinder overflow pipe drip after I have used hot water?
  • There are several reasons why this could happen, the first thing to etablish is if the overflow pipe is dripping or running.
  • If the overflow is dripping this is most likely normal expansion, that occurs when a hot water cylinder is in a heating cycle. It is normal for a 135L cylinder to expand up to three and a half litres of water in a heating cycle.
  • However if there is water running out of the overflow pipe, it will require attention and can be caused by three things –
  1. A faulty thermostat, which is not regulating the temperature of the element. This can cause the cylinder to reach dangerous temperatures, in the region of 90 – 99°C. As a safety measure the overflow pipe will start to run, in time this will reduce the temperature of the water and stop the overflow, and then the cycle will begin again. 
  2. It could be that the pressure reducing valve is faulty or has dirt inside it. This would mean that it is delivering the water at a higher pressure than allowed. 
  3. It could also be caused by back pressure, this normally occurs when a low pressure cylinder is installed. Often a new mixer will be installed which is not an “All Pressure” mixer and allows the mains pressure from the cold supply to flow back into the hot water system. This causes to much pressure in the hot water system, which is released either by the relief valve or open vented overflow pipe.

If you are encountering any of these problems, don’t delay call us now on 021 575 554 as you could end up with higher power and water bills.

2. What is a safe temperature for my hot water to be set at?

A safe temperature for hot water coming from your tap is 55°C. At this temperature a serious burn to a child’s skin will take 10 seconds. Even safer is 50°C. This allows about a minute before a serious burn occurs. The recommended temperature of hot water coming from the tap in rest homes and child care facilities/schools is 45°C.

On the otherhand though you can get Legionella Bacteria growing in your hot water cylinder if the temperature of your cylinder is set below 60°C, so that is why it is recommended that a tempering valve be installed. This allows your hot water cylinder to be set between 60 – 65°C, but the water to be delivered anywhere from 35 – 70°C.

If you would like to have a free, no obligation estimate done for the installation of a tempering valve, don’t hesitate to call us now on 021 575 554.


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