3.2: Water Loss
Learning Objectives
After reading this section, you will
- Differentiate among real losses
- Differentiate among apparent losses
- Prioritize leak fixing
If you were asked to picture water loss, you would probably think of a leak. Water is definitely lost through leaks. In this section, you will learn about types of leaks, but there are other ways systems lose water as well. As a general rule, you can estimate the amount of loss in a system by subtracting total consumption from total production.
Real losses include leaking pipes, joints, fittings; leaks from reservoirs and tanks; reservoir overflows, and improperly open drains and system blow-offs. Real losses are typically used (in terms of a percent of total production) to show how efficient a water retailer is in managing its assets. You can think of real losses as three primary types:
Reported leaks - These are the most dramatic leaks that end up in the local newspaper. These have high flow rates, but a relatively short run time because they are reported. They can be disruptive to staff (Stop everything and fix this!) as well as the customer (Why don’t I have any water?)
Unreported leaks —These are hidden underground. They may have low to moderate flow rates, and often very long run times. How would a utility find these leaks? They would need an active leak detection program of some sort or the leak would need to increase in flow to become noticed on the surface.
Background leakage —All systems have weeps and seeps. The flow rates are generally too small to be detected and not cost-effective to be fixed (until the leak escalates).
Keep in mind that as much as customers like to have water under relatively high pressure delivered to their homes, and high pressure is necessary to make it up to the top of hills in your service area, high-pressure systems are much more likely to leak than lower pressure systems.
Leaks are wasted water and money, but there are other consequences too. Wet areas may be liabilities for a water supplier and create a slippery surface or even a sink hole where people may get hurt.
Misconception Alert!
Many people think of real losses as the only type of loss. But there are losses that occur in all sorts of ways, which you’ll learn about below. Imagine what has to happen from the meter read to the actual delivery of the bill. Inaccuracies can be introduced in any number of ways.
Real losses are not the only source of leaks; they are just the most obvious ones. Water can be lost because of under-recording customer meters or theft. These are considered apparent losses. With an apparent loss, water may not be actually lost from the system. You can think of apparent losses as stemming from these sources:
- Customer metering inaccuracies—It is considered a best practice for all connections to be metered (though in some communities this is certainly not the case). Metering allows customers to make a connection between the volume of water used and the cost of water. It also provides information for water resource planners in terms of consumption trends. As meters age, they slow down. Without a meter replacement program, a water utility could easily be under billing based on customer metering inaccuracies.
- Customer billing system errors and data handling errors—Think of the process to get information from the customer meter to the customer water bill—there are a number of steps, including the actual read of the meter and transfer of information into the customer information system to billing. At any point in data transfer, an error can occur, but data errors can also be introduced in the analysis if estimates are used or accounts are closed or not transferred between customers.
- Unauthorized consumption—You would be surprised how much water is stolen! Yes, intentionally stolen! This could be an illegal opening of a fire hydrant, illegal connection, or tampering with a meter. Some customers will reactivate their own service connection after the service connection has been terminated for non-payment.
As you can see, there are a half dozen ways a water utility can lose water. The biggest reason for recovering water that was lost through real and apparent losses is revenue. This is literally money that is lost, whether it is by a medium-sized leak underground, a broken main above ground, theft, or meter reading errors. Other than weeps and seeps, all of these losses can be fixed, and usually cost-effectively.
Try It!
- If a water agency tracks the difference between consumption (the sum of all meter reads) and production (the sum of all water pumped from the ground or imported), would the difference between consumption and production be real or apparent losses?
- What is the relationship between pressure and leaks?
- What might be an argument to implement a leak detection program?
Glossary
- Apparent losses—Losses from customer metering inaccuracies, customer billing system errors and inaccuracies, and unauthorized consumption (theft)
- Background leakage—Weeps and seeps that have small flow rates and are not cost-effective to fix
- Real losses—Leaking pipes, joints, fittings; leaks from reservoirs and tanks; reservoir overflows and improperly open drains and system blow offs
- Reported leaks—Leaks that are reported with high flow rates, but short run times
- Unreported leaks—Leaks that are most likely hidden underground with moderate flow rates and long run times