Water pressure regulator (C) Carson Dunlop Associates How to Diagnose & Repair Building Water Pressure Regulators & Water Pressure Reducing Valves

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Water pressure regulator controls:

This article describes how to diagnose & repair a bad water pressure reducing valve or water pressure regulator that can result in either building water pressure and flow that are too weak, or building water pressure that is dangerously high. Distinguishing between static water pressure, dynamic water pressure, and water flow rate can help diagnose water problems in a building.

Here we explain these concepts and we describe how to measure water pressure and flow at a property where either municipal water supply or a private well and pump water supply is in use. Our sketch at page top, courtesy of Carson Dunlop, shows the key components found where municipal water supply enters a building.

We also provide a MASTER INDEX to this topic, or you can try the page top or bottom SEARCH BOX as a quick way to find information you need.

What is a Water Pressure Regulator or Pressure Reducing Valve, Where are They Installed, Why?

Example of a low pressure regulator Watts 123LPArticle Contents

What's the difference between a water pressure regulator valve and a water pressure reducing valve?

Looking over water safety and flow control products offered by Watts, that company lists a range of low pressure regulators and a wide range of high capacity water pressure reducing valves.

We notice that in low pressure regulation applications such as on steam heating systems and on residential water supply systems, control valves are referred to as low pressure regulators (Watts 123LP low water pressure regulator for example - sketch at left).

Series 123LP Low Water Pressure Regulators are used in residential and point-of-use applications to regulate water pressure in piping systems that require low pressure regulation. ... Maximum Working Pressure: 200psi (13.8 bar), Adjustable Pressure Range: 10 to 30psi (69 to 207 kPa), Reduced Pressure Setting: 25psi (172.4 kPa).

Most of the pressure regulators we see listed refer to low pressure applications on steam systems, residential water systems, or fuel oil systems.

Watts high capacity water pressure reducer Watts LF223

igher capacity water pressure reducing valves are used in commercial or industrial applications (and some residential applications) where it is necessary to protect the building plumbing system (pipes, water heater tanks, relief valves, etc). from high incoming water pressures and also to conserve water usage.

(Watts LF223 lead-free high capacity water pressure reducing valves, for example - sketch at left).

Series LF223, LF223S Lead Free* High Capacity Water Pressure Reducing Valves are used in commercial, industrial, and institutional applications to reduce incoming water pressure for protection of plumbing system components and to reduce water consumption.

It consists of a Lead Free* brass body construction (2 1/2 in. is iron), enlarged diaphragm, spring cage and seat orifice for super capacity, sealed spring cage for waterworks pit installations and an optional thermal expansion bypass. ... Maximum Working Pressure: 300psi (21 bar), Adjustable Reduced Pressure Range: 25 to 75psi (172 to 517 kPa), Standard Pressure Setting: 50psi (345 kPa).

Watts 127W high capacity pressure reducing valve

Watts and other manufacturers produce a wide range of types of water pressure regulators and water pressure reducing valves to handle fluid types, operating pressure ranges, and also responsiveness where the drop in reduced pressure should be kept to a minimum even as the water volume demand varies widely.

An example of a commercial grade high capacity water pressure reducing valve, the Watts Model 127W is shown at left.

In our articles we use the terms water pressure regulators and water pressure reducing valves interchangeably as referring to devices that both regulate the pressure or flow of water from a supply source into a building, and (if high water pressures are present) protect building plumbing systems from excessive water pressure damage by reducing incoming high water main pressure (that can be more than 150 psi in some communities) to a safe level (typically 50 psi) in the building.

OPINION: even after you've seen these two prototypical sketch of a low pressure water regulator and a higher-capacity water pressure reducing valve, in the field, rather than guess which water pressure operating range was intended by the device you're looking at, look for a model number or part number instead.

Water pressure regulator control (C) Daniel Friedman

Why are water pressure regulators installed on water supplies? Often municipal water supply pressure can run quite high, say over 80 psi and in some communities, more than 150 psi.

Our photo (left) shows typical incoming municipal water piping at a building. From left to right we see a main water shut off valve, a water meter (wires lead to an outdoor water meter reading device), a water pressure regulator, and water piping rising into the building.

This high pressure would cause leaks at many ordinary residential plumbing fixtures like sink and tub faucets or toilets, as well as some actually dangerous conditions - see WATER PRESSURE TOO HIGH: DANGERS. So where city or municipal water supply pressures exceed 80 psi, the building should have a pressure reducing valve, also referred to by some as a water pressure regulator installed, usually right after the water meter where water enters the building.

Building Code Requirement for Pressure Reducing Valves

In fact most national and local plumbing codes require that a water pressure reducing valve should be installed at buildings where municipal water supply pressures (in the water main in the street) exceed 80 psi. Excessive water pressures can burst pipes, cause dripping faucets, and can even cause rupture and explosion of both cold water pressure tanks and hot water storage tanks.

Examples of Pressure Reducing Valves Used to Regulate Municipal Water Supply Pressure

According to Watts Corporation, a producer of water pressure reducing valves,

There are two types of water pressure reducing valves, direct acting and pilot operated. Both use globe or angle style bodies. Valves used on smaller piping diameter units are cast from brass; larger piping diameter units are made from ductile iron.

Direct acting valves, the more popular type of a water pressure reducing valves, consist of globe-type bodies with a spring-loaded, heat-resistant diaphragm connected to the outlet of the valve that acts upon a spring. This spring holds a pre-set tension on the valve seat installed with a pressure equalizing mechanism for precise water pressure control.

Direct-Acting Pressure Reducing Valves in Residential Properties

In residential properties the pressure regulator likely to be encountered is a direct-acting pressure regulating valve such as the models shown in photographs on this page. Direct acting pressure reducers automatically reduce the incoming water pressure from the municipal supply or water main to a level that is less likely to cause operating or safety problems in the building. Quoting again from the Watts Corporation,

Water entering the valve from municipal mains is constricted within the valve body and directed through the inner chamber controlled by an adjustable spring loaded diaphragm and disc. Even if the supply water pressure fluctuates, the pressure reducing valve ensures a constant flow of water at a functional pressure, as long as the supply pressure does not drop below the valve's pre-set pressure.

Watts produces a Watts Governor 80™ used for this purpose, but other manufacturers also produce a wide variety of water pressure regulators.

How to Regulate Very High Incoming Water Pressure: Pressure Reducers in Two Stages

Serial pressure reducers - Watts Corp.

For very high incoming water supply pressures, a two-stage serial reduction method is used:

two pressure reducing regulating valves are installed in series.

The sketch of serial pressure reducing valves (left) is courtesy of Watts Water Technologies and appears in "Water Safety & Flow Control" by that company.

The first pressure reducing valve (for example a

Watts Model U5B) reduces incoming water pressure to 150 psi, and

the second valve reduces water pressure to 50 psi.

Importance of Selecting the Proper Pressure Reducing Valve

If your building already has a water pressure reducer installed, it may be defective or it may be set too high, or the wrong model pressure regulator may be installed.

If the wrong pressure reducing valve model is installed it may not be operating at the water pressure range and flow rates for which it was designed.

The result can be poor performance, noisy plumbing, poor water flow at least at times, not enough water pressure under high-draw conditions, or Wire Draw Leaks at Pressure Reducers and even dangerous building conditions or risk of building leaks and flooding under low water flow conditions. A more complete catalog of high water pressure problems is found

Using Parallel Pressure Reducing Valves for Better Maximum Building Water Flow Rate

Parallel pressure reducer schematic - Watts Corp.

Variations in building occupancy levels: Where building demand for water flow varies widely, a single pressure reducing valve may not be able to handle the maximum water demand flow rate.

This condition occurs at buildings where there is a large water supply main to an apartment or office building whose water demand can vary enormously (0.5 gpm to 100 gpm) depending on the building occupants. Watts and other pressure reducing valve producers recommend a nice solution to this problem (Image at left, courtesy of Watts Controls).

As Wattsand other manufacturers suggest, parallel pressure reducing valves are sometimes installed to correct this difficulty. One pressure regulator control is set at a higher psi flow rate than the other.

For example installing a Watts Model 223 pressure reducer set at 50 psi in parallel with a second Watts 223 pressure reducer set to 60 psi will allow increased total water flow capacity during periods of peak water demand.

Water pressure regulator (C) Daniel Friedman

he water pressure regulator can be adjusted to improve building water pressure and thus flow, by loosening a lock nut on the regulator and screwing the adjustment screw up or down a few turns.

Our photo (left) shows the water pressure regulator (photo bottom) and the regulator screw and lock-nut.

Be careful not to set the building water pressure too high, as you'll cause leaks.

For details on adjusting a municipal water pressure regulator

Watch out: don't set the water pressure reducing valve higher than necessary.

Doing so wastes water and as we discuss
at WATER PRESSURE TOO HIGH: DANGERS, setting water pressure too high can cause both plumbing problems and actual serious safety hazards at buildings.

Auxiliary Bleeder Pressure Relief Valves for Thermal Expansion Relief

Watts Corporation points out [in their discussion of their Watts Auxiliary Thermal Expansion Pressure Relief Valve No. 53, Serie3s 530C, 30L, or 111] that a pressure reducing valve may sometimes be ineffective due to high incoming water pressure from the municipal water supply system.

To protect the building heating, hot water, and plumbing system from thermal expansion pressure buildup during intervals of unusually high incoming water pressure, an auxiliary or bleeder pressure relief such as the Watts 530C valve can be installed on either a hot or cold water supply pipe and over a convenient drain location.

Watts also reminds us that some national and regional plumbing codes require that the maximum static water pressure should be not more than 80 psi (5.5 bar). See Definition of Static Water Pressure.

Expansion tanks to relieve high water pressure:

An alternative to installing or changing a water pressure regulator when building water pressure is occasionally 80 psi or higher is the installation of an expansion tank to temporarily absorb that pressure increase. Proper use of an expansion tank can help avoid unnecessary opening of the pressure/temperature relief valve on a hot water heating tank or a hot water heating boiler.

At HOT WATER PRESSURE EXPANSION RATE we discuss how we measure water pressure and how temperature changes affect water pressure in a closed water heater tank or heating boiler. For a discussion of temperature and pressure relief safety devices also


Causes of Variation in Building Water Pressure

As we discuss in more detail
at WATER PRESSURE VARIATION CAUSES, there are several causes of variation in building water pressure:

  1. Number of plumbing fixtures being run at once
  2. Variation in municipal water delivery pressure
  3. Variation in small community water systems and private well pump water delivery pressure Details are
  4. Water pipe diameter, length, elbows and bends:
    See Definition of Static Water Pressure

    and Definition of Dynamic Water Pressure.
  5. Clogged water pipes reduce water flow rate, not water pressure.
  6. Variations in building occupancy levels

How do we Diagnose Poor Municipal Water Pressure & Flow in a Building - 5 Key Checks

Key things to check when water pressure and flow are inadequate in a building served by municipal water supply are

  1. The condition of individual plumbing fixtures, faucets, valves, and controls. A clogged sink or shower strainer will cause bad water pressure at individual fixtures while others may flow freely. A plumbing shutoff valve that is partly closed or clogged with debris will cause bad water flow at that fixture.
  2. The incoming municipal supply pressure. The municipal water supply source may be delivering water at low pressure.
  3. The condition of water piping between the building and the street water main. An older water supply pipe connecting the building to the water main in the street may be small in diameter, clogged with minerals, rust, or debris, or it could be leaking underground.
  4. The condition of building water supply piping. Clogged pipes due to minerals or rust, small diameter piping, long piping

    For details about the above items,
  5. The setting of the water pressure regulator at the building water meter or water shutoff valve. This topic is discussed just below.

Photograph of a water pressure regulator on municipal water supply

Bad water pressure regulator or bad pressure regulator adjustment: (poor municipal water pressure) if the building is connected to a municipal water supply there may be a water pressure regulator installed, usually close to the water meter or where the water supply pipe enters the building.

If the water pressure control was set too low to start with or if there is a problem with the water pressure regulator, you may see an improvement in water pressure by diagnosing and adjusting or repairing this control.

If the loss of water pressure was sudden, it's not likely to be a problem the pressure regulator except in the less common cases of a blockage or failure in the regulator itself. In this photo our flashlight lights up a (rather amateurish looking) water pressure regulator installed on a municipal water supply.

You can see that a previous connection to the water meter was cut, left shut off (see that shutoff valve at the left hand vertical pipe - what happens if someone opens that valve?), and new fittings were installed to conduct incoming water to the building water supply piping.

The use of smaller diameter flexible copper tubing might restrict the incoming water flow, but the presence of a pressure regulator at all suggests that the incoming pressure may have been excessive. (Too high water pressure leads to fixture leaks.)

Details about how to adjust the building water pressure regulator or pressure reducing valve are found

Increasing the building water pressure by adjusting the pressure regulator (or a pump pressure control switch) will not fix a poor water delivery rate from the source (municipal water main or local private water pump), but if the pressure was set too low to start with you may see an improvement by this adjustment. If your loss of water pressure or flow was sudden, it's not likely to be a problem with the pressure regulator except in the less common cases of a blockage or failure in the regulator itself.

Watch out: don't set the water pressure reducing valve higher than necessary. Doing so wastes water and as we discuss
at WATER PRESSURE TOO HIGH: DANGERS, setting water pressure too high can cause both plumbing problems and actual serious safety hazards at buildings.

Water Pressure Diagnosis & Improvement Articles


Continue reading at WATER PRESSURE REGULATOR ADJUSTMENT or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.

Or see WATER PUMP PRESSURE CONTROL ADJUSTMENT to adjust the pressure output of a pump and tank water system,

Or see WELL WATER PRESSURE DIAGNOSIS for details about diagnosing poor well water pressure and flow

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WATER PRESSURE REDUCER / REGULATOR at - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.


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