Although we don’t look at general cold water use in our Home Energy Masterplan as the energy content and CO2 content of mains water is very low – 0.079g/litre – I thought I’d do a quick post to show what we have done and how it compares.

Based on our water meter readings we are currently using just less than 100m3 per year or around 68 litres per person per day. This is costing us around £287 a year. This also works out at around 0.08 tonnes CO2 in total. That’s not too bad considering there are 4 (and a half if you include our day time childcare) of us and the house is occupied 24/7.

How does that compare to UK averages? The usual rule of thumb is 150 litres per person per day. All good so far. According to Thames Water, we’re using the same as a 2.5 person low use household i.e. not much showering, washing toilet flushing.

I can assure you that we’re all washing enough, and with two little boys there is a lot of clothes washing too.  How is kept low?

• The key is that all the toilets are low flow.
• The next most important thing is that we have low flow showerheads installed. These save both the volume of water and also the amount of heat that is required for hot water.
• Our washing machine and dishwasher are both highly rated in terms of both energy and water use.
• We tried as far as possible when designing our pipework layout to reduce the distance from the hot water cylinder to the taps to eliminate dead legs.
• We don’t leave taps running when brushing teeth or washing up.

What we don’t have is tap aerators. If you don’t leave taps running then these are not very useful. You definitely don’t want them on sinks or baths that you fill – you’re after a fixed volume and so something that slows the rate of flow is just going to annoy you!

Another thing we don’t have is a Combismart.  This is a thermostatic device that holds water back in a combi boiler until the water is hot enough.  They therefore save both luke warm water and wasted cold water as you wait for a shower to heat up.  Why don’t we have one? Only because we don’t have a combi – if we did I definitely get one installed.