How Do Industrial Regulators Work?

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A regulator does not need power, instrument air, or any other electronic or pneumatic control devices. Let’s discuss why that is so.

A regulator is a classic force balance machine. Two forces are set up in opposition, and as the balance between the two forces change, different actions take place. If we look at the simple diagram below, we see a set screw, spring, diaphragm, and plug.

The spring and the diaphragm represent the two opposing forces, and the plug acts on the balance between the two. We use the set screw to show the regulator how much pressure we want by turning it to compress the spring. A compressed spring generates a force tending to push downward which in turn opens the plug and results in more flow. As the flow builds up pressure downstream, that pressure acts as an upward force on the diaphragm. This upwards force balances the downward force of the spring. The plug stops moving toward open and the flow and the pressure are now balanced.

Now let’s suppose the downstream demand for flow decreases causing more pressure to build in the downstream line. This will upset our force balance. The increased downstream pressure will exert more upward force on the diaphragm, causing the plug to move toward closed. This limits the flow to prevent further pressure build up. As the diaphragm continues to move upward, the spring is being further compressed, and the downward force it exerts increases. Once the downward force from the spring equals the upward force from the diaphragm, we are now back in the force balance condition and the flow and the pressure are now balanced once more.

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Frequently Asked Questions About Household Water Pressure Regulators

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A household water pressure regulator reduces the water pressure from potentially high pressure of a public water main to a pressure that is usable by the customer and compatible with normal household plumbing and fixtures. It also helps prevent pressure surges from entering the household plumbing from the public water main. High water pressure can result in dripping faucets and damaged water pipes, and it can damage fixtures and appliances. Sometimes, however, the device itself can develop problems. The repair will often require a new regulator, but knowing what kind of problems can occur with this equipment can help users to minimize the cost of the eventual collapse.

A pressure regulator is a spring-loaded automatic valve that regulates pressure on the downstream (house) side of the valve. Altering the spring compression changes the downstream pressure.

The pressure regulator should be installed just downstream, (on the house side) of the water meter.

The best way to know if the pressure regulator is working is to install a pressure gauge on each side of the regulator. If the upstream gauge reads higher than the downstream gauge, then the regulator is probably working. If there are no gauges, you might notice symptoms of pressure regulator malfunction. These include sustained or initial bursts of unusually high pressure at faucets and showerheads and water being discharged from the relief valve of your water heater.

A Typical Pressure Gauge

A homeowner or a plumber can use manufacturer’s instructions for adjustment. The adjustment mechanism is usually a screw on top of the regulator. Turning this screw changes the spring compression. Generally, turning the screw clockwise increases house water pressure and turning the screw counter-clockwise reduces house pressure. Repair kits for rebuilding pressure regulators are usually available from the manufacturer.

NOTE: Do not adjust your regulator if pressure drops or rises until you have checked your plumbing system and/or contacted the water utility.

A drop in pressure could be caused by the utility main or a leak in your plumbing. Contact the utility company about a possible pressure drop on the lines in your area and check your plumbing or have a qualified professional check your plumbing. Increasing your regulator setting could be harmful to your plumbing once the system has been restored to normal operations.

A rise could be caused by water expansion due to the water heater.

Most homeowners set their pressure at approximately 50 pounds per square inch (psi).

Note: According to the theory, the rate of leakage through a hole in a pipe is proportional to the square root of the pressure, determines how pressure affects leak rates. However, using measurements in real water distribution systems it has been found that pressure has a much greater effect on the leakage rate than the theory predicts. To illustrate this point, doubling the pressure in a pipeline will increase the theoretical rate of leakage by approximately 40%. However, in practice the real increase in the rate of leakage is typically 100%, and increases as high as 570% have been reported. So lower settings will help conserve water and prolong plumbing and fitting life while higher settings will have the opposite effects.

Why must I have a pressure regulator if the water pressure at the public main is low or moderate?

There are two reasons:

  1 - Most public water mains are supplied by pumps or pressure reducing valves. This equipment may produce temporary high pressure surges, which can be transmitted to household plumbing. A properly operating household pressure regulator will help prevent these surges from entering your plumbing.

  2 - Your municipality might increase the pressure in the main that supplies your house.

The property owner is responsible for installing and maintaining the pressure regulator, as well as any and all damage associated with the failure of it. The property owner is also responsible for any and all damage caused if there is no regulator.

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Typical House and Irrigation System Pressure Regulator Valve and Shutoff Ball Valve Arrangement in Sun City

Typical Pressure Regulator Valve Data Plate

Directions for Adjusting a Pressure Regulator Valve

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