Every wondered how much a dripping hot water tap costs you in wasted energy? Well it will cost you approximately **R106 per year**

This estimate was derived as follows:-

An internet search revealed that the average volume of a water drip is 0.4 ml. If we make the following assumptions:-

- A hot water tap drips every 10 seconds
- The water heater is set to 60 °C
- The cold water temperature is 20 °C
- Energy costs R1.5 per kWh (Ekurhuleni June 2013)

The the tap will waste:- 6 (drips per minute) X 60 (minutes per hour) X 24 (hours per day) =** 8640 **(drips per day)

The volume wasted will be :- 8640 (drips per day) X 0.4 (ml per drip) / 1000 (ml per litre) = **3.456** (litres per day)

The energy to heat 3.456 litres from 20°C to 60°C is :-

3.456 (litres) X 4200 (Joules per litre per °C) X (60 - 20) (temperature rise) =** 580608 **(Joules per day)

but 1 kWh = 3.6 MJ

580608 (Joules per day) / 3.6 . 10^{6}(Joules per kwh) =** 0.16 **(kWh per day)

Annual energy cost = 0.16 (kWh per day) X 365 (days per year) X R1.5 (Cost per kWh) =** R87.6 per year**

But 3.456 litres per day is 1.26 kl per year which in Ekurhuleni will cost you a further **R19.24** in water (R10.455 per kl) and sewerage (R4.815 per kl) charges giving a total cost of **R106 per year**. That's a lot of money to waste on a drippng tap considering the last time I bought one, a new tap washer was only R 0.15 !