All About Water Flow Meters

The device that can measure the flow of water in a pipe is called a water flow meter. Flow meters, used for a wide variety of liquids, gases, and steam are in use all over the world sensing the flow of water in a variety of applications and processes. There are many different flow meter technologies that are suitable to measuring the flow of water in a pipe. Each flow meter technology type offers something unique that allows them to be best suited for different types of applications.

A water flow meter can measure, monitor, and help to control the flow of water through a pipe, hose, or other manner of conveyance. It can provide a continuous reading of the water flow rate. Many flow meters for water can also perform other functions essential to different applications, like batching precise amounts into a process or totalizing the total volume of flow for a certain specified time frame.

A water flow meter is simply a subset type of flow meters. Flow meters can be used with a wide variety of different media besides water. So, all water flow meters are flow meters, but not all flow meters are water flow meters as some flow meters are not designed for use with water.

Based on the different flow meter technology types, there are many flow meter technologies that can handle the measurement and monitoring of water. As a generalization, the only flow meter technology type that is not the best choice for water are positive displacement flow meters as they generally require viscous media or media with lubricating properties to protect the gear mechanisms.

The other most popular flow meter types, that typically are used for water are magnetic flow meters, ultrasonic flow meters, variable area flow meters (also known as rotameters), paddle/flap/vane/target flow meters, differential pressure flow meters, paddle/pelton wheel flow meters, turbine flow meters, vortex flow meters, Coriolis flow meters, and thermal dispersion flow meters. Visit our flow meter technology articles to learn more about any specific water flow meter technology type.

Each technology type varies in its ability to function correctly with different water properties. For example, magnetic flow meters cannot process water that doesn’t have a sufficient minimum conductivity. So even though magnetic flow meters can be compatible with water, they are only compatible with certain types of water.

It is important to understand how the properties of the water to be measured determine which water flow meters will work for your application. Other examples of water types would be water with particulate matter, water with bubbles, aggressive water, salt water, pure water, deionized water, potable water, distilled water, dirty water, process water, and many other characteristics that can determine the appropriate choice of a flow meter for a particular application. Another consideration would be the temperature of the water in the application. Certain technologies and specific flow meter models are more limited in their temperature capacities than others.

Which flow meter you choose depends on other application variables as well, such as do you need switching, alarm, totalizing, or batching capabilities? Do you need a flow meter that can handle a large variation in flow rates, which is also known as turndown? Will the flow be turbulent? Will it be installed indoors or outdoors? Will the flow direction be vertical or horizontal? There are many other factors than just the media that go into choosing the correct water flow meter.

Based on where they are being used, there are three main usage categories of water flow meters: industrial, municipal, and residential/personal. Each of these broad application areas can help determine which types of water flow meters are appropriate for the exact need.

The variety of application areas where industrial water flow meters are used is almost endless. Because industrial processes often require a great deal of precision for the process or product, flow meter accuracy is usually a prominent consideration for industrial applications, as opposed to someone who just wants to know how much water their garden hose may be consuming. Industrial flow meters also need to be durable and reliable. Industrial processes can be demanding as far as high pressures, high temperatures, and the continuous operating time that the flow meter is in service. While a cheap little plastic flow meter with a simple readout of flow may suffice for a garden hose that is in service a few minutes or hours a week, industrial water flow meters are usually installed in heavy-duty processes that run 24-7.

Because shutting industrial processes down usually means less product is produced and less money is made, industrial water flow meters need to offer the lowest amount of maintenance possible. Again, while it costs a homeowner nothing to clean any accumulating gunk out of a little plastic flow meter, it can cost businesses thousands of dollars to shut down processes as it often means removing whole sections of process line for inline flow meters. This is the reason that insertion and clamp-on flow meters are used in certain applications and are becoming more popular as they reduce or eliminate the downtime required for any maintenance or calibration.

Industrial water flow meters may also need to perform additional tasks that are not possible with other flow meter types. For example, industrial processes may require totalizers that calculate exactly how much water was used in total or for a predetermined time frame. Batching control is also a common need in industrial applications, where the flow is stopped after a certain quantity has been dispensed into the process.

Municipal flow meters also require accuracy. When someone comes to read your water meter on your house to generate your bill, they want to make sure that they have accurately accounted for the water usage, so they do not charge you too much or too little. Residential or personal use water flow meters are usually small, inexpensive, and not designed for heavy-duty frequent usage. The cost of industrial water flow meters can vary greatly in price, depending entirely on the demands of the application.

Hot water flow meters are used in many different applications. The most important requirement for hot water flow meters is a high temperature tolerance for both the flow meter materials and any integral flow meter electronics. Most hot water flow meters will be made of metal as various plastics are not suitable for high temperatures. Some hot water flow meter models will place any sensitive electronics away from the flow body to help isolate them from the high operating temperatures. Certain flow meter technology types do not lend themselves well to hot water measurement as the principals of operation limit the maximum temperature capacities. Some common hot water flow meter technology types are Variable Area (Rotameters), Differential Pressure, and Vortex.

Industrial processes can produce what is known as “wastewater”, which can be comprised of any number of elements in addition to water. To monitor or measure the flow of this after-the-process-water, wastewater flow meters are needed. Wastewater is also a term commonly used for sewage. Many typical water flow meters are not suitable to be used as wastewater or sewage flow meters.

Flow meters for cooling water are used in a wide variety of water-cooling circuits in many different industries and applications. They are commonly used to ensure that the water is flowing at a rate that enables the cooling system to maintain proper process temperatures. If the water is not flowing sufficiently and the process area is not cooled enough, the product could suffer quality issues.

One example of a cooling application is MRI machines where water cooling is used to keep the coils cool. This application requires a water-cooling flow meter with good accuracy, high turndown, and the reliability of no moving parts, like our DUK Ultrasonic Flow Meters.

Steel mills also use a lot of cooling processes like cooling for castings. Induction furnaces that create the heat to process the metal generate high magnetic fields that would affect certain types of flow meter technologies like magnetic flow meters. Metal processing applications also require a heavy-duty build that can withstand the rigorous process conditions.

Water flow meters for pumps are used to verify that the pumps are doing their jobs correctly. They are typically inline flow meters. They need to provide an accurate representation of the flow rate being produced by the pumps, so higher accuracy is normally a necessity for water flow meters for pumps. If the pump and process is creating a lot of pressure, then higher pressure capabilities would be required from the flow meter. Flow meters can also be used to protect pumps as pumps should not operate without the media flowing through them. Flow meters can verify that sufficient flow is occurring to eliminate pump burnout from them running dry.

Most flow meters offered in the US will be available in units of gallons per minute, or GPM. The exception to this would be flow meters that measure flow by other units like feet per second, or pounds per hour. KOBOLD offers an extensive line of flow meters that provide flow rate readings in gallons per minute or gallons per hour.

Water flow meters with digital displays come in a wide variety of options. Choosing one version of a digital display over another version depends on both the functionality that the flow meter needs to provide and the cost. Simple displays that cost less may be more than enough to display a simple ongoing rate of flow. More complex digital water flow meters can display meter functions like totalizing or batching. Some can show different variables simultaneously on the display and others can be programmed to show different variables depending on the process requirements. Display screens can vary in visibility so make sure the option you choose will be readable at the place of installation if it is being read in-place. Another consideration is the power source for a digital water flow meter. Some are battery powered and others are externally powered.

Inline flow meters are flow meters that have an integral “flow body” that is installed in between two sections of pipe via connections on the inlet and outlet side of the flow meter. The measuring tube in the flow body becomes part of the piping. There are many types of inline water flow meters. Most any flow meter technology is available in inline installation models. There are many different types of process connections to secure the meter into the piping system. Common connection types in the US are male or female NPT thread, ANSI flanges, Tri-Clamp, socket connections, hose connections, and weldable connections.

The advantages to inline flow meters are that they are available in technology types that do not have any protuberances within the flow stream. That reduces the possibility of wear and tear or damage. Certain inline models can also offer less straight run requirements than insertion models, depending on the exact flow meter technology type. Inline meters can generally provide a more accurate reading than a similar insertion counterpart. KOBOLD has one of the largest flow meter lines in the industry and offers countless inline flow meters that are suited for water measurement.

Insertion water flow meters are installed in a method that is different from inline flow meters. Insertion meters can be introduced into an existing system with much less system disruption as they do not require pipes to be disassembled as inline flow meters do. Instead, a hole is introduced to the current pipe and the probe is fitted into the flow stream. Any electronic display elements are kept outside of the pipe and are either affixed to a surface or are held up by the long rigid probe body.

Insertion water flow meters also offer the advantage of easier removal for periodic cleaning or calibrating. Some models, like our PIT Insertion Magnetic Flow Meter, can be supplied with a supplemental extraction device that does not require system shutdown while the meter is being removed. Insertion water flow meters are also a good choice when the installation area is cramped or difficult to get to. It only requires access to the desired entrance point for the probe.

Clamp-on flow meters are almost exclusively ultrasonic technology due to the inherent measurement principle that does not require media contact like other flow meter technologies. They are referred to in many ways including strap-on flow meters and portable flow meters. Clamp-on installations can be temporary or more permanent in nature depending on the method used to affix the transducers to the pipe.

Ultrasonic technology requires that the pipe have sufficient conductivity to carry the acoustic signals. Because clamp-on installations do not intrude into the pipe, it is ideal for water applications where the water is contaminated or has large particulate matter that may damage other flow meter installation types with sensitive measuring elements.

As mentioned above, water flow meters come in all sorts of shapes, sizes, technologies, and have a variety of different features. Most water flow meters are going to be inline installations, inserted into the pipeline via integral connections on each side, the inlet and the outlet, of the flow meter.

Insertion water flow meters require a hole to be made in the pipe and a connection to be added to the pipe that can screw into the process connection on the flow meter. Clamp-on flow meters are simply affixed to the outside of the pipe with a permanent or removeable strap or chain.

How you read the rate of your water flow meter will be determined by the technology type of your water flow meter. For instance, variable area flow meters are typically read on the top of the float that sits inside a glass or plastic tube. Other flowmeters will offer a mechanical scale where the arrow moves up or pivots to show the rate of flow. Other types offer an output that can power digital displays. Visit our article to learn more about how to read a flow meter.