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Flow Restrictors & Regulators

How Do I Reduce the Flow Rate of Water?

To reduce the water flow rate of domestic or industrial applications, devices called flow restrictors are used. They are placed into the line of flow and essentially reduce the space that the water can flow through. This in turns decreases the flow output, for example a flow rate of 5 gallons per minute is reduced into a flow of 2 gallons per minute.

What Do Flow Restrictors Do?

Flow restrictors essentially create a barrier to the flow, decreasing the available area for the flow to move through. This decreases the flow output and less gallons per minute are released by the pipe or hose. Slowing down the flow rate cuts down the total water consumption/usage happening per minute.

A pipe or hose has a fixed cross-sectional area that the media flows through. Because of the fixed cross-sectional area, flow rate becomes a function of pressure where and increase in flow is a function of an increase in pressure. If you would like to control the flow within a fixed cross-sectional area with variable pressures, you need to accommodate the area in which the media flows.

To keep a constant flow, increasing pressure would need less cross-sectional area. This is where our REG Flow Restrictor excels. The passively activated, no power required, star leaf-spring mechanism decreases cross sectional area with an increase in pressure that keeps the flow rate constant. Our star leaf-spring will keep the flow constant between a differential pressure of 29 and 145 PSI.

Flow Restrictor Differential Pressure Curve

What Does a Flow Restrictor Look Like?

Flow restrictors can look different based on the purpose and the model. The thing that they all have in common is that they are designed to restrict flow by reducing the available area for the flow to move through. The shape of the element that restricts can look different, what they are made of can be different, and where they are installed can be different. They generally will have the same common piping thread for installation that is used in the US, an NPT threaded connection.

Shower Flow Restrictor vs Industrial Flow Restrictor

What is the Difference between an Industrial Flow Restrictor and a Shower Flow Restrictor?

Most shower heads purchased today will either have flow restrictors already installed/integrated within the shower head or will be included in the shower head package as an optional element to place within the shower head. This is to control water consumption and they have become more prominent in recent years due to an increased awareness of domestic water consumption.

Some shower flow restrictors are added as an additional link in the plumbing line itself, in between the shower head and the supply line. The housing for these will typically be metal like the supply piping, but the inside will be plastic. Both integral shower flow restrictors and added flow restrictors may offer multiple different plastic disks that are interchangeable and can be swapped out to allow different rates of gallons per minute flow. A typical flow rate for a water restrictor used in shower applications is 1.5 or 2.5 gallons per minute. Shower flow restrictors are usually plastic and are not built for rigorous service.

Industrial grade flow restrictors can also be used as shower flow restrictors. They are installed in the same way that the external shower flow restrictors are, in between the supply line and the shower head. Because they are made of more durable materials, the risk of them breaking and requiring an expensive trip by the plumber to fix is eliminated. The cost of an industrial grade flow restrictor is much less than plumber fees.

Industrial flow restrictors are used in a wide variety of industrial applications and deliver much higher pressure and temperature capabilities than simple shower restrictors. They also can be built for much larger line sizes and offer flanged connections in addition to threaded connections.

They are used anywhere that flow rates need to be held to a steady rate with no significant variation in the flow rate. Because flow restrictors only allow a predetermined amount of water through, the flow rate is constant on the downstream side of the device even if it is highly variable on the upstream side of the device.

Mechanical flow restrictors, like KOBOLD’s, are self-actuating. The force of the flow in the pipe creates the energy for operation and they do not require power to operate, nor do they require any pneumatic lines. This reduces the total elements involved in flow restriction. There is less to break and cost savings are delivered by only requiring one element instead of multiple elements to restrict the flow. They will also operate in areas where there is no power source and will continue to operate if there is a localized power failure.

What is the Difference between Flow Restrictors, Flow Regulators, Flow Limiters, and Balancing Valves?

Flow restrictors, flow regulators, and flow limiters are used interchangeably. They are all ways to describe the exact same result that they deliver: restriction, regulation, and limitation of a flow. Sometimes the word “valve” is also added on to these first three terms as well. For example, flow restrictor valve. The word “valve” is a general term used very broadly for something that slows or shuts off flow. The tap to a garden hose is a “valve”.

Balancing valves are sometimes also used as an interchangeable term for flow restrictors, but that is incorrect as their usual meaning is a bit different from the others. Balancing valves are used in HVAC applications to maintain certain flow conditions within a heating or colling system to assure that the heating or cooling function is operating the same system wide. If a system is “balanced”, it is operating correctly. If a system is “unbalanced”, then it results in situations like some tenants of an apartment building being delivered too much heat and some tenants not receiving hardly any heat. Balancing valves also control flow, but the nuance of what they do is a little different than flow restrictors.

What is the Difference between a Flow Restrictor and a Flow Meter?

A flow regulator is a device that restricts and reduces the amount of liquid flowing through a pipe. For example, it can reduce a flow rate of 10 gallons per minute output to 5 gallons per minute output by reducing the space that the water is able to flow through. Flow regulators do not measure the rate of flow and cannot perform any additional process functions.

A flow meter is a device that monitors, measures, and controls the flow of liquid though a pipe. It calculates the rate that the media is traveling at and can also perform other process functions such as switching, batching, and totalizing to allow for process control. Sometimes, both flow meters and flow regulators are used in the same process line to measure and control the flow.

Flow Regulator vs Flow Meter

Where are Domestic Flow Restrictors Used?

  • Shower Head Flow Restrictors
  • Reduction of Water Flow in a Fountain
  • Reduction of Water Flow from a Tap
  • Reduction of Water Flow from a Garden Hose
  • Flow Regulators for Washers

Where are Industrial/Commercial Flow Restrictors Used?

  • Fluid Metering, Controlling Flow Throughput
  • Actuator, Cylinder, or Motor Speed Control
  • Inkjet Printing
  • Medical Applications
  • Chilled Water Balancing
  • Semiconductors
  • Reverse Osmosis Systems
  • Water Flow Regulation for Stills
  • Food and Beverage

How Do Flow Restrictors Work?

For our industrial flow restrictors, constant flow is achieved by two stainless steel spring plates that are crosswise mounted and riveted together. The gap between the spring-loaded stainless-steel plate and the seal-surface is continuously varied as the differential pressure changes. As the differential pressure decreases, the gap widens, and it closes as the pressure increases, thus maintaining a constant flow volume through the device.

Flow Restrictor Components

Why Reduce Water Flow Rates with a Flow Restrictor?

For residential purposes flow restrictors can deliver cost savings by reducing unnecessary water use. For example, a shower producing 1.5 gallons per minute can probably do the job just as well as a shower producing 2.5 gallons a minute. The difference in the cost of one gallon per minute times the minutes your shower is running for a year can add up. As water scarcity becomes more prevalent in certain geographical areas and environmental concerns become more mainstream, it is considered responsible to eliminate any water wastage. Flow regulating valves can help in that goal.

The reasoning also stands true for industrial use. It can save money by reducing unnecessary water waste. In industrial applications they can also protect any sensitive equipment from spikes or lulls in flow rates and can better temper flow rates for any precision functions involved in the measurement process.

Is a Flow Restrictor Necessary?

For domestic applications, certain areas that are prone to drought have to strictly control water consumption. Flow restrictors can help lessen the amount used for each task and allow for more tasks to happen with the same amount of water use. In areas where water is not monitored as closely, they can still deliver cost savings.

Do you have to have one installed in your shower for your shower to function? No, they can usually be easily removed, either from inside the shower head or from the supply line. Removing them will effectively increase the flow output of your shower.

For industrial applications, if you require your flow to be held to a constant in your process line, a flow restrictor could be the answer to extreme flow variations. Reducing these variations reduces the necessary turndown requirements of any flow meters placed downstream of the flow restrictor.

Here is an example. Say a process line experiences a flow of 5 to 20 GPM but the desired flow meter for the process can only accommodate a maximum flow rate of 15 GPM. If a 15 GPM restrictor is installed upstream of the new flow meter installation, the turndown accommodation is now less, and the 5 to 15 GPM meter can be installed.

Does a Flow Restrictor Increase Pressure or Reduce it?

A flow restrictor will increase the pipe pressure on the upstream side of the restrictor. The increase in back pressure, coupled with the decrease in orifice size that the water can come through, results in a decrease in flow rate output (gallons per minute) but an increase in the flow speed and force.

A common example would be a garden hose. When it is flowing unobstructed from the bare hose end, the water does not travel very far, it basically falls out of the hose end and onto the ground. When a sprayer head is added to the garden hose, what happens? The water travels much farther with much more force, but less water is coming out of the hose per minute.

If you want to use the garden hose to fill up a bucket, will it fill up faster with the sprayer head on it or off it? Obviously, it will fill up faster without the restricting sprayer. But if you want to use the same hose to spray dirt off your sidewalk, do you want to use the open hose or a sprayer head? Obviously, a sprayer head is the best choice for this use because it delivers the water with an increased force and speed (but a decreased output of gallons per minute).

In short, a flow restrictor increases pressure on the upstream side of the restrictor. The flow output is decreased in water output per minute, but the force with which it comes out increases.

How Do I Install a Flow Restrictor?

For domestic uses, if a flow restrictor is not already integral to the appliance or device distributing water, a flow restrictor can be installed in the supply line before the device. To do this, the flow restrictor installation will need to be “inline”. This means that the current continuous supply line will need to be disturbed or replaced. One pipe or tube will connect to the upstream side of the flow restrictor, and one will connect to the downstream side. This will effectively insert the flow restrictor into the supply line. Ensure that the inlet and outlet connections on the flow restrictor are compatible for connection with the supply line ends.

The same installation process applies to industrial applications. The flow restrictor is installed inline to the piping system through connections on the flow restrictor and connections on the pipe. To install our industrial flow restrictors, here are some guidelines.

  • Remove any packaging parts left in the device.
  • Make sure that the permitted maximum operating pressures and temperatures for the device are not exceeded.
  • Install the flow limiter into the piping without mechanical stress.
  • Protect the measuring pipe against external damage.
  • Avoid pressure surges in the measuring pipe or blocking the flow quickly.
  • If possible, after mechanical installation, make sure that the connection between screw connection and pipe is tight and does not leak.
  • Inlet and outlet run: our flow restrictors do not require any inlet and outlet runs.

How Do I Remove a Flow Restrictor?

Flow restrictors that are not integral to shower heads are removed by unscrewing the device and reconnecting the two supply lines that were on either side of the device inlet and outlet. For integral flow restrictors, inspect the inside of the shower head and look for a small disc that is able to be removed.

What is an Inline Water Flow Restrictor?

Flow restrictors (flow regulators or limiters) are “inline” devices. This means that the body of the device is integrated into the piping system. Inline water flow regulators require pipe moderations to install into an existing line.

As opposed to flow meters, which can have insertion models where just the measuring element is inserted into the pipe through a hole, inline devices require that the piping be disassembled and reassembled with the device between an inlet side pipe and an outlet side pipe. Flow meters also come in clamp-on models, which are ultrasonic flow meters that are affixed to the outside of the pipe and the pipe is not disturbed in any way. Flow restrictors are generally “inline” devices only.

Where Do I Buy a Flow Restrictor?

Looking to buy a flow regulator recognized for it’s durable and dependable service? Do you need one that requires no power and is self-actuating? Do you need it to handle pressures up to 2,900 PSIG or temperatures up to 572 °F? Would you like one made in the USA that can be delivered quickly and is a top seller globally? We suggest our REG Automatic Flow Regulating Valve available in either brass or stainless steel.

How Much Do Flow Restrictors Cost?

Depending on whether your flow restrictor needs are domestic or industrial, flow restrictors can vary widely in cost. Simple plastic domestic flow restrictors can be purchased for less than 10$. More rugged and industrial models will cost more but compared to most industrial instrumentation they are relatively cheap. View the cost of our REG Flow Restrictors in our online store.

Who Makes Flow Restrictors?

KOBOLD is a global instrumentation company that designs, manufactures, sells, and supports a wide range of products for flow, level, pressure, and temperature. Our flow restrictors are an industry standard for reliable passive flow restriction. Our unique flow regulators are an all-metal construction, delivering great value by ensuring a long service life. To learn more about KOBOLD or to talk with one of our expert engineers, please call us now and we would be happy to help you find your ideal application solution for free.

Learn more about why you should partner with KOBOLD for your application.

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Automatic Flow Regulating Valve
REG - Automatic Flow Regulating Valve

Made in the USA | Passively Activated | Brass or SS | Up to 2,900 PSI | Up to 572° F | 0.13...10.56 GPM


KOBOLD USA is a subsidiary of KOBOLD Messring GmbH, a world-leading instrumentation engineering business founded in Germany in 1980 by Klaus J. Kobold. With patented technology and superior service, the company quickly established itself as one of the global leaders in sensor and control systems with high quality products. The KOBOLD brand name became synonymous with superior quality and technological advancement in instrumentation engineering.

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