Why Your Hot Water Runs Out So Fast | And What Actually Fixes It

You could wind up with three baths out of the tank. You are lucky to have made one before the water is shot off. Here are the real reasons – the obvious ones as well as those that no one ever checks.

One of the most frequent complaints we are receiving within the whole of Sydney is the lack of hot water. And the amusing fact is that it is hardly an isolated dramatic letdown. It is normally a progressive deterioration process as soon as the showers become shorter, the water becomes slightly colder and finally you may find yourself in a situation where you can not fill the bath without the water fully running cold half way through. When a person calls, they have been changing their behaviour about a worsening system months before.

The real causes, in descending order of frequency, and what corrects each, are these.

1. Sediment on the Tank Floor

This is the most widespread reason for diminished hot water capacity, and least diagnosed. Minerals in Sydney’s water supply (calcium carbonate at 50–57 mg/L, classified as soft to moderately soft) slowly settle out as sediment on the bottom of the tank. This sediment layer accumulates over years and replaces water that the tank has the capacity to retain.

A 250-litre tank, containing 30 litres of sediment upon the bottom is an effective 220-litre tank. The water warms to an equivalent temperature, though with less water. The slowness of the accumulation lets you not gradually feel a noticeable difference but only a gradual degeneration of capacity.

The fix: A tank flush. We empty out the tank by draining it, stirring up the sediment, and clearing it out the drain valve. This in most instances revives the original capacity. It is a service job to be done every three or five years, but has it been done by a single tank in Sydney?

2. Heating Element failed or Failed

Electric tanks contain a single or a pair of heating coils which are fitted into the tank and heat the water directly. Over time, mineral scale builds up on the element surface, insulating it from the water and reducing its heating efficiency. Finally, the element either overheats and burns away, or it short circuits and the breaker blows.

A partially failed element warms up the water more gradually and to a lower final temperature. You get warm water rather than hot, and the interval between uses takes anywhere between an hour and several hours.

The remedy: Replacement of elements. A new element costs $100–$200 for the part, plus labour. When it is heavily scaled, too we empty the tank of the loose sediment which was insulating it.

3. Thermostat Low or Failing

A thermostat located on a hot water tank regulates the desired temperature usually, 600 C on a storage system. Should it be switched off (possibly by a person to save energy, or by chance when searching into something unrelated), the water will not come to a practical temperature. A faulty thermostat can incorrectly detect the temperature of the water, switching off the element before the water is adequately heated.

The fix: We check and recalibrate the thermostat. Should it be faulty, it can be easily and cheaply repaired by replacing the thermostat.

4. Tempering Valve Issues

A tempering valve introduces cold water into the hot water exiting the tank to provide safe temperature at the tap – 50 0 C in bathrooms (to avoid scalding) and 60 0 C in the tank to kill legionella bacteria. When the tempering valve is adjusted too low, maladjusted or partially clogged, it incorporates an excessive amount of cold water. The cause of the result is as though you are running out of hot water, when indeed, the tank is not the problem, but the valve is.

The fix: Adjust, repair or replace the tempering valve. It is among the less noticeable causes and almost always overlooked by homeowners who troubleshoot it themselves.

5. The System Just Is Under-sized

In fact, sometimes the system has not fallen into an infertile rut, it was only small to begin with. A 50-litre tank put in a studio apartment that has now been occupied by two people is going to run dry. A 160 litre tank that supports a family of five with teenagers will not cope with the morning rush. Capacity can be the root issue, in case you have added individuals to the family since your system was installed.

The solution: Have a bigger tank, or change to a continuous flow design that supplies endless hot water, no matter how large the household. In the case of families with the high simultaneous demand (two showers, dishwasher, washing machine are all operating simultaneously), the gas continuous flow can be quite a feasible solution.

6. Off-Peak Tariff Timing

When your electric tank is fed on an off-peak tariff, then it will not heat at any time other than at specially allotted off-peak times- usually at night. When you exhaust the hot water supply during the day, and your off-peak heating period does not commence until late in the evening, before that time you will have no hot water at all. It is natural functioning and not a vice, but it surprises people.

The solution: Switch to a fixed tariff (price per unit of electricity will be higher, but the tank will heat up whenever you need it), add a time-clock that gives you a boost in the middle of a day, or install a more efficient heat pump that warms using inexpensive solar electricity should you be able to install solar panels.

The first thing we check on a “running out of hot water” call is the simplest: when was the tank last flushed? In most cases, the answer is “never.” A flush, an element check, and a thermostat test solve the majority of reduced-capacity complaints. It’s an hour of work that restores years of lost performance.