Every June the same call comes in: the hot water used to last through three showers and now it gives up halfway through the second. Sometimes the heater is failing. More often it is working exactly as it did in summer, and the season has changed the sums.
Why winter is harder on a tank
The cold water coming into your house in a Melbourne winter is several degrees colder than in summer. You set the shower by feel, so in winter you mix in more hot and less cold to get the same warmth. The same tank simply empties sooner. It also takes longer to recover, because it is lifting colder water up to 60 degrees. Showers run longer in cold weather too, and pipes under the floor lose more heat on the way.
What you can check yourself
- The size and age on the label. A 125 or 160 litre tank is small for four people, and most storage tanks last 8 to 12 years.
- The tariff. An electric tank on a controlled or off-peak load only heats overnight, so once it is empty it stays cold until the next night.
- The relief valve drain pipe. A slow drip while the tank heats is normal. A steady stream all day is hot water going down the drain.
- The base of the tank. Rust stains or a damp slab mean the cylinder is on its way out.
- Every hot tap in the house. If one shower is lukewarm and the rest are fine, the fault is at that tap or its mixer.
Signs of an actual fault
Water that is only ever warm from an electric tank often means one of its elements has gone. A gas heater whose pilot keeps going out usually needs a new thermocouple. Lukewarm water at every bathroom tap while the kitchen runs hot suggests a worn tempering valve.
When to stop and call
Do not take the covers off a heater. Thermostats, elements and gas controls are work for a licensed tradesperson. If you smell gas, turn it off at the meter if you can do that safely, leave the house and call from outside. As a guide, a tempering valve replacement is around $330 fitted, an element and thermostat about $380, and a like-for-like tank changeover starts from $1,650. If your tank is over ten years old and running short, it is worth pricing a bigger one or a heat pump before it fails on a Sunday night.