How do I fill in the 'water softeners' section of the Water Efficiency Calculator in the government's Code for Sustainable Homes?
As of November 2010, the Department for Communities and Local Government provides a Water Efficiency Calculator to help people comply with the Code for Sustainable Development. The section on ion exchange water softeners asks for four figures:
1) Total capacity used per regeneration (%)
2) Water consumed per regeneration (litres)
3) Average number of regeneration cycles per day (No.)
4) Number of occupants served by the system (No.)
A Harvey’s block salt softener uses 17 litres of water to regenerate. The softener will regenerate itself when a certain amount of water has passed through it. The amount of water is determined by a gear setting that will be set, based on the local water hardness, when it is installed.
If we assume a hardness of 315ppm - which is a higher level of hardness than is found in almost all English homes - then the gear setting would allow 520 litres of water to pass through before the softener between regenerations.
This gives us our answers for questions one and two:
1) 3.27%
2) 17 litres
The fourth question - the number of occupants served by the system - will of course vary from house to house. Let’s assume a high number again - say, five people.
4) 5 people
Now we are able to calculate the answer to question three. Because a Harvey’s block salt softener regenerates only when the household has used a certain amount of water, we cannot give an average number of regenerations per day without first estimating how quickly the occupants of the house will use water. This will depend on some of the other water efficiency figures that you’ll be working out - how many baths and showers, what kind of washing machine, etc. Let’s make another fairly high estimate for now - say, 120 litres per person per day. Multiplying this by our example figure for the number of people in the household - five - and dividing it by the amount of water the softener softens before regenerating - 520l - allows us to calculate the answer to question 3:
3) 1.15 regenerations per day
The Water Efficiency Calculator then goes on to put all these numbers into a formula, and works out how much water is being used beyond the 4% good practice level. Even with the high estimates we’ve used for this example, you will still be able to put a zero into the final table - the Harvey’s softener exceeds the good practice guidelines.
Results
- 100% This was helpful and informative