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Step #2
Water Meters and Flow Sensors

You may or may not have a water meter. If you buy your water from a water company or municipal water district you probably have a meter. If your water comes from a well, lake, or stream you probably don't have a meter. The water meter measures how much water you use, that way the water company can charge you for the amount you use. Even if you get your water from a water provider you may not have a water meter, I didn't have one at a couple of the homes I've owned (water was provided for a flat monthly fee regardless of how much was used.) If you do have a meter it will most likely be located near where your water supply taps into the water company's pipes. This is usually right next to the curb, or perhaps adjacent to an alley behind your home. In climates with extreme cold weather the meter may be under the house in the crawl space, or often is inside the basement. Many newer meters are electronic, they send your water usage information to the water company via wires or radio signals.

Flow Sensors (optional)

Some people install their own water meter, or flow sensor, on the irrigation system. This allows them to monitor how much flow the irrigation system is using. Typically an electronic "flow sensor" is used for this purpose rather than a water meter like the water companies use. The flow sensor typically creates an electronic pulse when a given amount of water has passed through it, for example a cubic foot of water. The flow sensor connects up to the irrigation controller that is used to turn on and off the irrigation system. Some higher-end models of irrigation controllers have the ability to monitor the number of pulses from the sensor and use the data to determine how much water has been used and to evaluate the irrigation system performance. For example the controller might detect that the flow is higher than normal, indicating a leak in the irrigation system, or maybe a broken sprinkler head. Likewise a flow that is lower than expected might indicate a valve did not open when it was supposed to. The controller then sounds an alarm, or may shut off the water to limit damage from the leak. Flow sensors and controllers that monitor flow are features that are common on many larger irrigation systems, like parks and golf courses. Now, as the price of the equipment drops and water conservation becomes an issue in more places, homeowners are starting to implement these optional flow sensing features as well.

If the meter is buried in a box, be careful when you open the box. Over the years I've encountered just about every creepy thing one can imagine in those boxes! Turtles, rats, snakes, various dead things. Ants and spiders are most common. It's not a bad idea to be prepared to jump back, and maybe have a can of bug killer handy when opening a underground box. Once you find the meter you will likely need to clean it off so you can clearly see it. The meter should have a size stamped on it, if not, call your water company and ask them for the meter size, it should be in their water billing information. The pressure loss in water meters is based on the meter size and the flow rate.

The charts below give typical pressure losses for various meter sizes and flow rates. If your meter is a combination of two sizes (like 5/8 x 3/4) use the smaller size. These dual-size meters are made by taking a small meter and putting a larger size inlet and outlet on it. So it is really the smaller size meter. For flow sensors you will need to contact the sensor manufacturer to find out how much pressure loss to expect in your unit. Flow sensor losses are generally less than those for a standard water meter, so if you can't find a manufacturer's flow loss table, in most cases you can safely use the values in the water meter tables below for flow sensors.

Find your meter size below, then use your "Initial Design Flow" (from your Design Data Form) to find the PSI loss. Enter the PSI loss from the table below on the water meter line of the Pressure Loss Table. If you don't have a water meter just enter 0 on the table.

5/8" meter:
5 GPM	1 PSI loss
7 GPM	2 PSI loss
9 GPM	3 PSI loss
11 GPM	4.5 PSI loss
13 GPM	6 PSI loss
15 GPM	8.3 PSI loss
Don't exceed 15 GPM

3/4" meter:
4 GPM	0.5 PSI loss
8 GPM	1 PSI loss
11 GPM	2 PSI loss
14 GPM	3 PSI loss
17 GPM	5 PSI loss
20 GPM	6.5 PSI loss
Don't exceed 20 GPM

1" meter:
8 GPM	0.5 PSI loss
13 GPM	1 PSI loss
19 GPM	2 PSI loss
23 GPM	3 PSI loss
26 GPM	4 PSI loss
29 GPM	5 PSI loss
32 GPM	6 PSI loss
34 GPM	7 PSI loss
Don't exceed 34 GPM

1 1/4" meter:
This is not a standard water meter size. If you have one it may be a 1 1/2" with a 1 1/4" inlet and outlet. But, then again, it might be a 1". What do you mean, that's not very helpful? Unless you are reasonably sure by looking at it that it is a 1 1/2", you should assume it is 1".