Tuesday, 11 July 2017

How much water is it OK to waste?

All water companies waste water through not fixing leaking pipes. This is OK up to a point. There is something called a 'sustainable economic level of leakage' which is the level where the cost of fixing leaks and the cost of not fixing them balances out, taking into account environmental costs. Obviously environmental costs are hard to put a finger on. So what is acceptable?

Leakage management is a high profile issue, and rightly so.
I decided to write about this today because of my work on the Water Customer Panel for South Staffs and Cambridge Water Company. Amongst other things we have to monitor their customer engagement work in preparing the next 5 year business plan and I have enjoyed the opportunity to observe some focus groups on what people think should be priorities for our water company. Leakage management is always mentioned, and rightly so.

Typical leakage rates are a bit less than an extra person per household.
How much water does your water company waste? You can find out from the Discover Water website. There are different ways of measuring this. I think the easiest for comparison purposes is the leakage per household. On this measure the latest results show Southern Water is best with 77 litres/day/household and Thames is the worst at 171. South Staffs and Cambridge are both below the average which is a bit below the average consumption per person (139 litres/person/day). So the average leakage rate is a bit less than an extra person per house.

CompanyLeakage litres/household/day
S. Staffs

Let's not be hypocritical. We can invest in water saving at home too.
That sounds a lot but let's not be hypocrites. Do you waste water at home? Most people do. Some of this is due to carelessly leaving taps running, or luxuriating in the shower. Some is due to lack of investment in efficient appliances. For example, an old fashioned toilet typically uses 13 litres per flush whereas a modern low flush toilet uses 4 litres for a standard flush, 6 litres for a full flush (from Waterwise). On average 30% of our water use is for the toilet. Have you replaced your loo yet? Let's look at the payback time for this.

Very roughly:

  • To purchase and fit a new toilet: £300 (though you could pay a lot more than this for an upmarket toilet!)
  • Water saved, say 8 litres per flush, 6 times a day = 48 litres/day
  • Cost of water: 0.24 p/litre (for me, at the moment, including sewerage charges).
  • Savings per year: £42.
  • Payback time: about 7.5 years.

Were you surprised? Of course if your water supply is not metered your savings will be zero.

There are lots of other ways to save water at home and some of them you might think are worthwhile, others not. You might think that paying an extra 10p for a luxurious shower is a very good deal, at least in purely financial terms. (See How much does your bath or shower cost.)

Calculating costs for the water companies is complicated.
The calculation above was very simple but for water companies it is much less so. For the economic level of leakage you have to take into account a whole range of costs. The following table lists some of these.

WhoCost of leakCost of fixing the leak
Water company (and ultimately you the customer)Energy costs of treating, storing and pumping extra water.
Cost of building and maintaining the infrastructure needed to treat and pump extra water.
Man hours and resources to find and fix the leak. (Just finding it can be a big job.)
PublicDamage caused by leak, such as flooding. Sometimes low pressure or even supply interruptions.Inconvenience of having the road dug up, traffic jams and diversions. (The company will also have to pay a charge to the council for this under the Public Services Utilities Street Works Act or PUSWA for short.)
EnvironmentExtra water taken from the environment.
Energy use and carbon emissions from treating and pumping the extra water.
Material use and emissions due to energy used while fixing the leak.

Costs vary from one place to another and one leak to another.
All of these costs vary from one place to another. For example, the costs of treating water vary depending on how clean it is to start with (aquifers are usually cleaner than river water). The damage caused by a particular leak depends on how much water is leaking and where. The cost of pumping depends on how hilly the area is. The environmental costs of extra water abstraction are much higher in places where water is scarce than where it is plentiful. This is a serious issue in Cambridge and population growth is making it more so. In this town leakage management is important not just to keep costs down but also to maintain supply.

On the other side of the table, the costs of fixing the leaks can vary from one place to another and one leak to another. Fixing a leak in a major road is a different game from fixing a leak in a quiet street or a rural road.

It is never going to be practical to fix all leaks.
Ultimately, big leaks tend to have high costs and get fixed quickly whereas small leaks may not be worth the trouble of even finding them, never mind fixing them. It is never going to be practical to fix all leaks, but it is important to keep the level down to a reasonable level - and what is reasonable depends partly on where the water comes from.

The more measurement points there are, the easier it is to locate leaks.
There are things that water companies can do to reduce the number of leaks, such as using good quality pipe materials and being careful not to stress joints with sudden changes in pressure. (Though weather and traffic also take their toll.) Also companies can improve detection of leaks by installing more equipment to measure flows. The more measurement points there are the easier it is to identify and locate leaks. In fact some of the leaks that the company is blamed for are our responsibility. Until everyone has a smart water meter it is hard to determine whether the leak is in the public bit of pipe or in our own houses.

There is a difference between the economic level of leakage and the sustainable economic level of leakage.
Most of the costs in the table above have some kind of financial element, even the environment ones, though it is arguable if they reflect the true cost. For example the Climate Change Levy paid by businesses for their energy use is currently about £10/tonne. However, the environmental costs of abstraction have no regulatory cost (except in certain cases for sensitive sites, through the Abstraction Incentive Mechanism). The Environment Agency is responsible for controlling licenses and this sets a limit to what can be taken but there is no charge for abstracting below this limit.

What all this means is that there is a difference between the economic level of leakage, where you fix all the leaks that are worth fixing in purely financial terms, and the sustainable economic level of leakage where you take all the environmental costs into account as well.

You might be asked your view.
If you are involved in a consultation with your water company, you could be asked your view: ultimately how much are you prepared to pay to reduce leakage levels beyond the economic level. Water companies are required to take our views into account in preparing their business plans for scrutiny by OFWAT. If we tell them that leakage is important then they will be allowed to spend more on this and also they will get a higher performance target. These targets really matter because there are rewards and penalties for exceeding or failing the targets.

What's all this to do with energy?
I have talked about the similarities between water and energy issues before. (See Think energy savings, think water savings too.) You can think of reducing leaks as investing in energy efficiency. The cost of extra abstraction and treatment if we do not is like investing in generating and distributing energy - which also has environmental costs. We make similar judgements when we decide whether (or when) to replace our old freezer with a more efficient one, or whether we can be bothered to find and fix the draughts or pay more for heating instead.

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