Ask RiotACT: Frozen pipes on new Hot Water System

A guy near Jindabyne (much colder weather than Canberra) told me that water freezing in pipes is an issue some mornings but they work around it by leaving a tap on slightly. Because water is always moving through the pipe, it does not get a chance to freeze.
As you have a new heat pump, I’d also be concerned that the heat exchanger itself is freezing. You get hot water because the heat pump takes heat out of the ambient air – which means that the heat exchanger will be colder than the outside air. Hence most heat pump systems have an electric heater in them to thaw out the unit so that it can work. Ask the vendor/installer if your heat pump is supposed to be able to thaw itself out.

Heat pump HWSs are cheap to run if they are installed as per directions (north side of house) but they only last as long as the sacrificial anodes last which is about 5 years. Then the water turns to gloop and the water input pipe fittings corrode.

On some brands it is almost impossible to replace them because of the inbuilt difficulty in accessing them and having the right tools.

At the end of the day they are not worth the electricity saving which can be equalled with a mains HWS with day/night off peak plan. Get a stainless steel one too.

Pipes underground won’t freeze unless the ground freezes, such as in Arctic areas that get permafrost. There I have seen pipes running in large conduits between the houses; heated I was told. The pipe could still freeze where it comes out of the ground.

I used to live in a house where the pipes froze at -3C. I lagged the pipes and then they went to -5 before they froze. If anyone got up in the night, they would run the water to free any ice that was building up.

A pipe burst one -7 morning. Not early, as the ice had to defrost first. I rushed outside when I heard a loud bang at about 11am. Water gushing in a fountain from a pipe on the outside wall. It was an old house and the pipes where a mixture of steel and copper pipes. It was the newer copper section which burst; not the older ‘cholesterol’ filled steel. The plumber informed me he had a long list of burst pipes that day to fix.

For our climate, any exposed pipes need lagging. Rubber tube lagging can be bought, or they can be lagged the old fashioned way, with old singlets and other waste cloth. The commercial product is likely more effective though.