I spent a few days at my brother’s house over the Christmas period and noticed that it took a considerable time for hot water to reach the tap in the en-suite. I felt that this was wasting a significant amount of water. I am in the process of planning my own home and wish to be as environmentally friendly as possible. Could you give me some advice on how I could eliminate such waste?

A considerable volume of water is lost each year by the running of taps until they become warm. Consider the cost of originally treating this water, and then heating it, only to allow it cool again while stored in the delivery pipe. The fact that water is then flushed away without use is literally washing your money down the drain.

In most homes, a single distribution pipe will run from the heat source with branch pipes run individually to each hot tap. When you consider the diameter of the pipe and the distance between the heat source and tap, the amount of water stored in these pipes can be significant. If the taps are not used for a long period, the hot water contained within the pipes will become cold. This cold water must be run off to allow hot water to reach the taps. The cold temperature of the pipe can also cause further delay by cooling the hot water as it passes through to reach the tap.

This is a problem which has generally been overcome in large-scale buildings, such as hotels. In a hotel environment, clients generally expect hot water on demand for 24 hours per day. The excessive running of taps until hot, would not only lead to customer dissatisfaction, but would also lead to waste of vast quantities of water. In large buildings such as this, hot water is circulated in a secondary looped system. This means that hot water is continuously circulated around the building with only short branch connections leading to bathrooms. The water in the secondary pipe is continuously heated by passing back through the boiler. Only the small quantity of water in the branch pipe will cool and be wasted.

When planning your own home, it is worth looking at ways to reduce this form of waste. It can be costly to have a secondary system and this type of system is only really efficient if water is heated continuously, and where there is a 24-hour demand.

With larger houses, the use of local forms of water heating should be considered. The use of electrical instantaneous type heaters can work in some cases, particularly where there is only demand for limited quantities of hot water. The use of small under-sink electrical heaters, with a small storage capacity and timer, is also worth considering.

When planning your home, the positioning of bathrooms, en-suites and taps should be such that pipe runs are kept to an absolute minimum. This will help to reduce the amount of wasted water when taps are run. Time spent planning your layout and considering the length of pipe runs will save you money in the long run and will make your new home more environmentally friendly.

Noel Larkin, Chartered Building Surveyor and member of the Society of Chartered Surveyors Ireland, scsi.ie