The testing of a water meter is very simple. It comprises checking the registration of the meter against the actual volume of water passing through the meter, as measured in an accurate volumetric tank or weighed on accurate scales. The value of water unregistered by meters with various percentages of slowness and differing amounts of water drawn through the meter. As per reports, water is valued at $3 to $5 per thousand gallons. So it can be obtained that with water at $3 per thousand gallons, the return on investment for testing and repairing a meter 4% slow will be only $12 with every 100,00 gallons of water used. It would require a large and active account for making frequent testing pay under these conditions. Again with water at $5 per thousand gallons, a meter failing to register 20% of the water passing through it would lose $100 for the waterworks industry for every 100,00 gallons. Under these conditions, testing will have a much better return on investment.
The practice of charging for sewage disposal and treatment as a percentage of the water bill puts additional emphasis on meter accuracy. Surcharges can be as high as 150% of the water bill, with 100% surcharges common.
If a municipality has a surcharge of 100%, the effect is that the water meter is measuring the bill for sewage service in addition to its normal function of metering water. With a water rate of $3 per thousand gallons and a surcharge of 100%, the meter is, in effect, measuring $6 of revenue, which provides more reason for accuracy. If sewage service charges are to be based on meter readings, it would be only fair for the sewerage authority to carry part of the cost of meter testing and repairing. Meter accuracy may be defined as the quotient obtained by dividing the quantity registered during a test by the actual volume of water. A meter registering nine gallons when 10 gallons are run through it has an accuracy of 9/10 or 90%. A meter registering 51 cubic feet on an actual volume of 50 cubic feet is 51/50, or 102% accurate. Meter accuracy is often expressed in percentage fast or slow, thus a meter that records 95 gallons when 100 gallons are run through it under registers or is slow by 5%. A meter registering 102 gallons on the same volume would be 2% fast. It is better, however, to express accuracy in actual terms, which would be 95% and 102% in these cases