A Letter from Badger Meters, Inc. in regards to Water Meter Performance
August 2005
Subject: Water Meter Performance
Dear Lori [Williams, TMWA General Manager]:
In accordance with your request for information regarding water meter performance, the following information is provided. Badger RECORDALL* meters are "positive displacement" type water meters. This means the meter measures all the water passing through the measuring element, not just a portion as inferential type meters do.
Positive displacement type meters are based on either the nutating disc or oscillating piston measurement principle. Badger Meter employs the nutating disc type of measuring element. These meters are designed to and comply with the American Water Works Association Standard (C-700) for potable, cold water meters. Every meter we manufacture is fully tested and must pass AWWA accuracy standards. An accuracy test result tag is attached to each new Badger RECORDALL meter at our factory before delivery to utility customers.
Regarding accuracy of positive displacement meters, after an extended period of time in use, accuracy will be less than when the meters were new. By design, positive displacement meters cannot increase their accuracies after being in service. As closely machined or molded sealing surfaces wear, water will "slip" by the measuring element without being measured. The result is a "slow" meter; a meter with a lower than accurate consumption total.
Badger Meter and independent testing agencies, as well as numerous water utilities in North America, test and evaluate meter performance continuously. A substantial body of statistical data shows that our meters hold their accuracies within AWWA Standards for 10 years or longer. Finally, mechanical wear due to consumption totals and water quality will begin to reduce efficiency or cause meters to "slow down."
We know that situations do arise in which the customer questions the accuracy of the water meter. This may occur when an old, worn meter is replaced by a new meter that more accurately measures water consumption. This higher accuracy level will result in a larger water bill for the customer. A leak in the customer's plumbing system or unusual usage of water may also result in an abnormally high water and sewer bill. For example, a leaky toilet can lose in excess of 10,000 gallons per month without even producing a ripple on the surface of the toilet bowl. If one can see a water ripple, the leak is frequently on the order of 1/2 gallon per minute or more. A flick of the toilet's flush handle and the leak stops momentarily.
Few people can relate a leaky toilet to thousands of gallons of water use on the water and sewer bill. In addition, people cannot appreciate how long the toilet was leaking, or that it happens again and again until it is properly repaired.
By design, the odometer in a drive meter cannot "jump" or have one of its wheels move out of sequence. Only if a component is severely damaged, a part is missing, or if the odometer was improperly assembled could such a condition occur. Likewise, the low flow indicator (small, triangular component on the dial face) cannot cause false registration on the odometer. The rotation of the low flow indicator is a response to the pulsating flow of water into the disc measuring chamber. This component is designed to show disc motion at even the lowest rates of flow, thus many Utility personnel refer to it as a "leak detector".
No outside force can influence or cause the odometer to jump without detection. Some forces can cause the odometer to stick, jam or slow down, but not to come out of engagement, "free wheel" or "jump" without producing visual evidence. These outside forces include mechanical, electrical, thermal or magnetic forces. It should be remembered that a sealed register is a mechanical device and, as such, cannot malfunction and then correct itself.
In the overwhelming majority of investigations regarding excessive consumption/odometer readings, the reasons have either been reading errors or unknown, undetected water use. One does not realize the amount of consumption that may result from a very small leak over a long period of time.
I hope this information is useful to your organization. I would suggest that you obtain a copy of Manual AWWA M-6 from the American Water Works Association. This is an excellent book regarding the selection, installation, testing and maintenance of water meters. If we may be of further service, feel free to contact us.
Yours truly,
BADGER METER, INC.
Mike Grafwallner
Application Engineering
