Shop Talk: The 3 Types of Water Meters

Hi there! I’m Megan McCallion, another Aquicore-ian project engineer. In this post, I’m going to go into detail about the three types of modern water meters

All three types of meter use different strategies to measure how much water is flowing through a pipe, and these differences mean that they are appropriate for different situations. We spend a lot of time thinking about which meter will be the most reliable in various client scenarios. At the same time, we balance this against the cost of equipment and the labor needed to install it to keep costs within our standard client budgets, which we try to keep as low as possible for obvious reasons.


In-Line Metering

The oldest and simplest type of water meter is the faithful “in-line” meter. These are pretty much exactly what you would expect from a water meter. The contents of the pipe being measured flow through the meter, turning a dial as they go.

There are still some advantages to an in-line meter. For one, they’re extremely easy to read if you’re taking readings the old fashioned way. Water consumption is displayed on the face of the meter, and because the measurement is analog, it is always up to date and accurate.

For small pipes in the 0.5″ to 2″ range, in-line meters are also the cheapest option. These meters are generally only a few hundred dollars. Once you get into pipes 3″ in diameter and above, though, they rapidly become more expensive than other options.

In-line meters are also more expensive to install. They require water to be shut off to the pipe because a section has to be removed and replaced with the meter. A lot of times, this can mean a whole building shutdown, which means the installation has to be done late at night or early in the morning.

Installation is also reasonably complex. A mechanical contractor might take a few hours to install an in-line meter or up to a day, depending on the job. If she’s installing a smaller meter, this generally makes up the bulk of the cost that gets passed on to the client.


Insertion Metering

Insertion metering is by far the most exciting kind of water meter to install! Sadly, it’s also a little too expensive and impractical for most situations. 

The name gives it all away: Insertion meters are essentially rods that are inserted into a pipe through a small hole. The meter sits on a “saddle” that fixes it to the pipe, and a measuring device is fixed to the end of the rod that sits inside the pipe.

The measuring device may be a turbine that uses kinetic energy to measure flow, or it may be an electromagnetic wave meter. Functionally, though, the two are basically the same.

The exciting part of installing an insertion meter is the art of the “hot tap.” Insertion meters only require a small hole, so they can be installed without turning off the water flow. The meter’s saddle comes equipped with a ball valve to keep water from going everywhere while you’re preparing to stick the rod in, but you’ve got to be quick!

Insertion meters are small, so they don’t require a long section of pipe, and they don’t take a long time to install. A mechanical contractor can usually hook one up in an hour or two. That said, they’re usually more expensive than either of the other meter types, and because installation requires specialized knowledge, you still need a mechanical contractor to make a trip out to the site.

In situations where pipes are not long enough for ultrasonic metering and a shutdown is not an option, insertion meters are the perfect fit. In most other situations, they aren’t the right choice.


Ultrasonic Metering

The most modern type of water metering, and the one that we use the most often, is ultrasonic metering.

Ultrasonic meters are more expensive than in-line meters most of the time, though they’re less expensive than insertion meters. Where they really shine is ease of installation.

An ultrasonic meter consists of two bands with a preset distance in between them and a central display. The bands fit around the pipe and send an ultrasonic pulse back and forth between them. The meter calculates the speed the pulse is traveling at and uses that to determine the speed of the water flowing through the pipe. 

Ultrasonic meters are extremely easy to install. They can be attached to a pipe and calibrated in no time, and no special expertise is required. There’s also no need to shut down water to the pipe, so installation can be done during the day. That means the electrician, who is already there to set up the rest of Aquicore’s hardware, can handle this part of the metering too.

The downside to ultrasonic meters is that they must be attached to a long section of straight pipe. Lengths vary by design, but you generally need about 20x the diameter of the pipe before the first band and 10x-20x the diameter after the second band. That means that an ultrasonic meter on a two-inch pipe requires 40″ before the first band, 20″-40″ after the second band, and a few inches for the distance between the bands. In some buildings, particularly older ones, this isn’t an option.

Submetering water usage can help to make billing more fair, especially in a mixed-use space, where some types of business might consume a lot more water than your residential tenants and some businesses use none at all. It can also help to avoid disaster: One of our clients experienced a weekend cooling tower malfunction that could have wasted 80,000 gallons of water a day had we not caught it, not to mention the water damage it could have caused.

With submeters installed strategically throughout your building, you can get a better picture of where resources are going and how to conserve them.

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