HomeMy WebLinkAbout12 Water meter replacement program Agenda Item # 12
IL
WORKSHOP
To: Board of Directors
From: Ed Taylor
Date: November 19, 2008
Subject: Discussion of Large Water Meter Replacement Program
1. WHY THIS MATTER IS BEFORE THE BOARD
This item is informational relating to the implementation of a Large Meter Replacement
Program.
2. HISTORY
The Water Department currently has about 670 commercial accounts. Any customer that is
not single-family residential (commercial, school, park, apartment building, etc.) falls into this.
category. These accounts are equipped with a meter and the meters range in size from 3/4"
to 8".
3. NEW INFORMATION
For revenue metering, there are three basic types of meters in the size ranges utilized by the
District.
1) Positive Displacement
2) Turbine
3) Compound
Positive displacement meters are available in sizes from 5/8" x 3/4" to 2" from a number of
manufacturers. These meters are quite accurate at low flow ranges, with a 2" meter having
about 99 percent accuracy at a flow of 2 gpm. A 2" positive displacement meter is rated for a
continuous flow of 80 gpm with a peak of up to 160 gpm.
Turbine meters are available in sizes from 2" to 20" from a number of manufacturers. Turbine
meters are very accurate for higher flow rates but will under-register at low flows. As an
example, a 4" turbine meter is 99 percent accurate at a flow of about 8 gpm but will barely
sense flows of 2 gpm or less.
A compound meter is essentially a small positive displacement meter and a turbine meter
combined into a single unit. The small positive displacement meter will measure the low flows
with the turbine meter measuring the large flows. Compound meters will normally have two
registers, but single register units are available.
For situations where higher flow rates are required, the usage patterns of the customer will
normally dictate the type of meter that is used. Turbine meters are less expensive than
compound meters, so the cost of the meter must be weighed against the revenue lost by
under-registration of low flows.
As an example, a park might normally have low flows of 0 to 10 gpm during the daytime
associated with drinking fountains and toilets. At night, while irrigation is occurring, flows
could easily exceed 200 gpm. Other customers such as apartment buildings, schools, and
hospitals will also have flows that vary widely throughout the day. In contrast, an irrigation
service to a golf course normally does not vary widely and does not have low flows. In the
past, the District has only installed turbine meters on its larger accounts. Compound meters
have not been utilized.
In November 2008, the General Manager directed the Water Department to review its meter
inventory regarding both meter type and age of meter and for its large accounts. It appears
that some of these large meters may be as much as 27 years old. Based upon this review, 20
accounts have been identified where the installation of a replacement meter may be
warranted.
If new meters are installed on these customers, it will likely result in an increased metering
accuracy and an associated increased monthly bill. The new meter would not result in a rate
change for the customer, but it would measure low flows that are not currently being
measured, increasing the volume charge to that customer. The District's Conversation
Department will be working with these customers to mitigate these increased costs.
It should be noted that compound meters are longer that turbine meters, and in some cases it
may be necessary for the District to upgrade the meter box to house a compound meter.
Prior to the installation of a new meter, the District will notify the customer that the meter will
be replaced and the meter box upgraded if necessary.
4. FISCAL IMPACT
The Water Department is currently conducting a field survey of the meter installations in
question to assess whether meter box upgrades are required. Once this review is complete, a
cost for the overall project can be developed.
5. RECOMMENDATION
Re is r port and provide comment.
Ed Ta for Michael D. Holley
Y
Water Utility Manager General Manager