Metro Water District

Dual Metering

What is dual metering?
How are sewer user fees calculated without dual metering?
Who qualifies for dual metering?
What paperwork is required to establish dual metering?
What does dual metering cost?
Who installs the dual metering system, and what are the requirements?
What sort of permitting and inspections are required?
Can I cancel dual metering at a later date?
How much will my reported usage be reduced with a dual meter?
How do I read my meter to determine usage over a defined period?
Is it possible to have leaks, even if the leak detector on the meter does not turn?
What should I expect my new sewer fees to be?
When can I expect to see lower sewer fees on my water bill?
How do I know if dual metering is really worth it for me?
Are there any other options to lower sewer fees?

What is dual metering?
Dual metering is having two meters on your property that lets you know how much water is used outside versus indoors so that your sewer fee is based on just your indoor water usage.  Dual metering is a means to subtract irrigation and other outdoor water usage from the overall water usage for the purpose of lowering sewer user fees.  It is accomplished by adding an additional meter placed after the existing domestic meter—branched off the customer’s private side for irrigation and other outdoor use—and having the customer isolate all irrigation usage to what passes through this additional “dual” meter.  The difference in meter reads between the total usage (existing meter), and the irrigation/outdoor usage (dual meter), will then represent the only usage used to calculate sewer user fees.

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How are sewer user fees calculated without dual metering?

Without dual metering (and assessing only domestic usage), Pima County assesses sewer usage fees based on a 3-month winter average (Dec/Jan/Feb) of all water usage through the existing meter, for the entire fiscal year starting July following this three-month average. This average is assumed to be the "minimum" monthly usage affecting the sewer system over the year, regardless of how much water actually reaches the sewer system from the house, is consumed, or is used outdoors for irrigation.  If usage in a month is lower than the average, Pima County will use this lower value to assess a lower sewer fee for that month, however sewer fees are not assessed on water usage higher than the calculated winter average.  Pima County does have an appeal process to accept and alternate 3-month period during the year for lower usage than the winter months of Dec/Jan/Feb.

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Who qualifies for dual metering?

If you are a District customer with an existing residential domestic water meter, and you pay sewer user fees (i.e. not on a septic system), you qualify for dual metering.  Commercial or multi-family customers do not qualify for dual metering, and are required to separate out domestic and irrigation usage with a dedicated irrigation meter.  Dedicated irrigation meters are already excluded from sewer fees.

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What paperwork is required to establish dual metering?

The customer will be required to sign a Dual Meter Agreement and Right-of-Entry to permit District personnel to set, maintain, and/or read the dual meter on private property. This document will be non-transferable with the property, and future owners or successors will need to sign new paperwork to continue with the dual metering program (no additional fees apply).

Dual Metering Agreement/Right-of-Entry

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What does dual metering cost?

There is an initial application fee established by the Board of Directors (currently $380) for the District to recover costs for materials, labor, inspection, and testing of a dual metering system.  This is due up front with the Dual Meter Agreement and Right-of-Entry, and is not eligible to be spread out among subsequent months of billing.  There will also typically be costs for the customer to isolate their private irrigation system and/or other outdoor uses from all other house connections, and reconfigure piping to feed all outdoor uses by the dual meter.  After the cost of the initial installation, the customer will incur an additional monthly fee in their normal billing of 1/3 the Water Availability Rate  of a standard 5/8-inch meter.  The most current Water Availability Rates can be found from the "Billing/Customer Service" tab at the top of the page, then choosing "Rates and Charges" for your particular service area.  If you already have a standard 5/8-inch meter account, the current Water Availability Rate is also shown on your billing each month. 

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Who installs the dual metering system, and what are the requirements?

The customer or their plumber/contractor is responsible for all installation and reconfiguration of the private system, except for the dual meter and the meter box (supplied and installed by Metro Water), after the reconfiguration is completed.  The customer installation will involve a tie-in to the private side of the customer’s service line, isolation of their outdoor uses from the house plumbing, and piping to reconnect these outdoor uses to the dual meter.  The dual meter is required to be within private property, and within 5 feet of the existing meter.  The customer will receive an upstream and downstream angle meter stop (AMS), a downstream dual check valve, and a “meter jumper” to be installed in place of the future dual meter.  The specific parts given to the customer, and further specifications about the installation, and installation examples can be found at the links below.

Dual Metering Installation Procedure
Dual Metering Installation Detail
Dual Metering Reconfiguration Example

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What sort of permitting and inspections are required?
The customer or their plumber/contractor are responsible to check with their municipality regarding any codes or permits necessary for this work.  Prior to installing the meter, District personnel will verify the maximum distance from the main meter is 5 feet, and will also verify the AMS fittings are installed 7-10 inches below the existing ground level per the detail (above).  After installing the dual meter and box, District staff will test to be sure outdoor use turns both the main and dual meters, and house use turns only the main meter.  A return visit and further inspection/testing will be necessary after customer corrections if deficiencies are discovered.

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Can I cancel dual metering at a later date?

Yes, termination of dual metering is completely up to the customer at any time; however, the initial application fee would be non-refundable.  The customer need only contact customer service to discontinue dual metering.  A service order will then be issued for District personnel to recover the dual meter and reinstall the “meter jumper” (so it can still function without the second meter), leaving all else in place.  If at some future date the owner (or future owner) wishes to re-establish dual metering, the same initial application fee and paperwork would apply, since there would be new inspections, and a new dual meter going forward once re-established.

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How much will my reported usage be reduced with a dual meter?

This will vary by customer, but you can estimate this reduction by reading your own meter to tally up how much water passes by the meter for each programmed irrigation cycle or other outdoor use.  It is not necessary to evaluate full irrigation cycles since the water used during each cycle should be constant over time.  For instance, if you have an hour-long cycle, you can record how much water is used in 10 minutes and simply multiply by 6 (to get usage for an hour). Then multiply by how many cycles in a month to get the total monthly usage for this cycle.  You would then do the same for all the other control valve cycles that occur over the month and add them all together.  For miscellaneous outdoor uses, like topping off your pool or washing a car or hand watering potted plants, you may have to use a representative trial, and then multiply by the number of times in a month this is typically done.  Adding all these outdoor uses together will then give you a monthly total for outdoor usage to compare with an overall usage from a recent bill (note that usage is reported in hundreds of gallons).  To estimate how much of your monthly usage reported to Pima County would be reduced, subtract your calculated total from the overall usage on the bill.

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How do I read my meter to determine usage over a defined period?

To evaluate how much water is going through your meter for any defined period, you need to obtain a meter read immediately before and after this period.  It is also imperative that there be no other usage occurring during your evaluation. Your meter is generally located along your property line/corner at the street or in an alley.  With all water use turned off in the home and outdoor, you first need to verify no leaks are occurring in the system.  This is done by observing the small red or blue star (or triangle) shaped leak detector on the face of the meter as shown below.  If there is any rotation of this detector when all water is turned off, you have a small leak that needs to be found and addressed.  You can find some guidance on leak troubleshooting in the Water Conservation area of the Education Corner page of our website.

Determining usage on a meter is similar to determining mileage on car odometer.  You simply subtract a beginning reading from an end reading for the total gallons used.

 

The right-most zero on the face of the dial above is not an active number but is simply painted on the meter face.  The last digit is represented by the numbers around the dial face.  The other zeroes advance like an odometer as water passes through the meter.  Each of the digits around the face represents one gallon of usage, so each of the small divisions is a tenth of a gallon.  Each complete revolution of the dial represents 10 gallons, and will cause the second zero from the right (the first “live number wheel”) to uptick one digit.  For example, let's say you had a beginning read of 0005230, with the hand on the dial pointing at the "3".  This means you have a meter read of 5233 gallons.  For your end reading, if the dial reads 0005250 with the hand on the "2", this means you are now at 5252 gallons.  You then simply subtract to find the gallons used for the defined period, or 5252 - 5233 = 19 gallons.  You can get down to the tenth of a gallon for beginning and end if you want, but the closest whole gallon is likely more than sufficient for your usage calculations.

You may have a meter that has radio-read features, that partially obscure the face of the meter, or are a different brand than the Badger face (above) such as a Zenner meter (below), but the same principle applies for how to read the large dial and number wheels.

In our Metro-Hub and Metro-SW areas, we utilize Sensus Iperl meters that are automatically read (AMR), and have a fully digital face:

The digital readout will electronically record usage through the meter up to a tenth of a gallon, as recorded on register, as well as indicate below the numbers even the slightest movement of water through the device (with a "plus" symbol).  The same principle would apply for calculating gallons used over a defined period, by subtracting the ending number from the beginning number.

A full description of how to read and interpret iPerl meters can be found at How to Read the iPerl on the Sensus website.

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Is it possible to have leaks, even if the leak detector on the meter does not turn?

Yes.  While a dripping faucet or hose bib will cause the leak detector to move, having a toilet that leaks into the bowl, and only refills the tank periodically, will likely not be detected (unless you happen to check right when the tank is filling).  Periodic leaking outdoors is far less noticable also. As opposed to visible leaks with fixtures inside the home, leaks and overwatering with irrigation often only occur when the control valves open for a watering cycle.  This generally occurs in the middle of the night or early morning when these cycles are scheduled, often sight unseen by the homeowner. Before making any decisions about dual metering, customers should first manually switch on each control valve independently and verify leaking and/or overwatering is not occurring in their irrigation system.  Regardless of whether dual metering is being considered or not, we recommend you regularly monitor and maintain your irrigation system components. 

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What should I expect my new sewer fees to be?
To determine what to expect for new sewer fees, you need to first know what your current sewer fees are (from a recent bill).  Sewer fees are comprised of a volume rate (dependent on reported water usage) and a service fee (a base rate for sewer connection).  Only the volume rate is affected by a reduction in the water usage reported.  When you have calculated what all outdoor usage is per month (see above), you would then contact Pima County and verify what your new sewer fee would be if the use reported is reduced by this calculated amount (determination of sewer fees can also be found in the Pima County Code, Title 13, §13.24.030.C). This lower fee would then form the basis of expected savings to be gained each month to offset any initial or monthly costs of a dual metering system, and allow you to determine a cost recovery period.

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When can I expect to see lower sewer fees on my water bill?

Once a dual metering system is in place, ideally only the water going to the house (excluding the outdoors) will be reported to Pima County as usage subject to a sewer fee.  This lower, home-only usage will likely be less than the last calculated Dec/Jan/Feb winter average, so this lower usage will be used to calculate the sewer fee.  If this is the case, you should see savings in sewer fees as of the next full billing cycle.

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How do I know if dual metering is really worth it for me?

Since the usage and outdoor setup among customers differ, there is no general answer to this question, though it is possible for customers to determine given their individual circumstances.  To be cost effective for any customer, the savings received from lower sewer fees need to be substantial enough to recover the initial setup costs ($380), the reconfiguration costs to supply the outdoor uses from the dual meter (varies by customer), and the ongoing costs to read the dual meter each month (1/3 the Water Availability Rate for 5/8-inch meter), over a recovery period acceptable to the customer. Since upfront costs can potentially be substantial for reconfiguration, recovery of dual metering costs is generally harder for low or average outdoor water users, as opposed to customers with large amounts of year-round outdoor water use.  The most likely candidates are customers that own a combination of pools, orchards, large turf areas, large gardens, etc.  However, what each customer considers an acceptable recovery period is a personal decision based on their own circumstances.

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Are there any other options to lower sewer fees?

If it is possible to reduce/minimize outdoor usage during the winter months of Dec/Jan/Feb, this is the simplest means to minimize sewer fees throughout the year.  As mentioned above, if this is not possible, but there are three different consecutive months of the year when a customer can regularly use far less water (other than the winter months), you can petition Pima County to evaluate sewer fees using these other consecutive months that have a lower usage.  Targeted reduction, if possible, is the least costly way to lower your sewer fees apart from dual metering.  To reduce/minimize usage, this will likely involve making landscaping and other outdoor changes.  For some examples, this could mean only having summer grass (and letting it go dormant in winter without water) or removing grass altogether in favor of xeriscape, using more native low-water plants, more efficient and/or drip irrigation, using a pool cover to prevent evaporation, using a graywater/water harvesting system to offset the need for irrigation water, and other water reduction techniques.

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For all inquiries or assistance related to the above, please contact our general
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  • 6265 N. La Cañada, Tucson, Arizona 85704
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