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water pressure test gauge (C) Daniel Friedman Dangers of Excessive Water Pressure in Buildings
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  • What problems are caused by excessive water pressure in a building?
  • How do we diagnose & fix water pressure that is too high
  • Diagnosing a Bad Water Pressure Regulator at buildings connected to a municipal water supply
  • Questions & answers about the problems caused by building water pressure that is too high; diagnosis & cure of excessive water pressure; safety hazards of high water pressure;

This article describes the dangers of excessive water pressure in buildings: safety hazards include burst water tanks or boilers, clogged relief valves, and even building flooding and mold contamination.

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List of Problems Caused by Excessive Water Pressure in a Building

Also see WATER PRESSURE REDUCER / REGULATOR for a discussion of how we reduce building water pressure to a safe level and how we assure uniform building water pressure and flow using a pressure reducing valve or pressure regulator. See WATER TANK PRESSURE GAUGE and WATER PRESSURE GAUGE ACCURACY for a discussion of built-in water pressure gauges. Readers whose building is served by a private pump and well system should see WATER PUMP PRESSURE CONTROL SWITCH..

As we explain in more detail at WATER PRESSURE REDUCER / REGULATOR, often municipal water supply pressure can run quite high, say over 80 psi and in some communities, more than 150 psi. Some national and regional plumbing codes require that the maximum static water pressure should be not more than 80 psi (5.5 bar). Watts and other plumbing manufacturers recommend that a water pressure regulator should be installed in buildings where water pressure exceeds 60 psi. There are good reasons for this upper limit on building water pressure, as we list here.

To accurately determine the water pressure in a building using a simple water pressure test gauge, see WATER FLOW RATE MEASUREMENT.

If the building water pressure is too high, here are some problems that you may encounter

  • Banging or noisy water pipes when turning on or off water at a faucet
  • Spitting from the water faucet aerator when water is turned on
  • Short water heater life
  • Leaking faucets
  • Running toilets
  • Reduced washing machine or dishwasher life due to leaks
  • Septic drainfield flooding and failure if your building is connected to a private septic system
  • Increased sewer bill costs in communities who base their sewer charges on water usage metering.
  • Increased hot water heating costs: if water pressure is unnecessarily high, the increased volume and rate of cold water flowing through a home water heater increases the operating cost of that appliance.
  • Wasted water - running water at higher-than-needed pressure and flow wastes water in daily fixture use. Watts estimates that twice as much water flows through a plumbing system at 150 psi as flows at 50 psi and that "... much of this additional water is wasted."
  • Water heater tank explosions - see our warning notes below.
  • Wire Draw Leaks at Pressure Reducers are caused by excessive municipal water pressure, leading to relief valve spillage, relief valve clogging, possible BLEVE explosions or boiling liquid vapor explosion. Or less dramatic, building leaks that cause flooding can also lead to costly mold contamination.

Watch out: although normal municipal water pressure is under 70 psi, when the building's pressure reducing valve is set too high even if a water heater is protected by a thermal expansion bypass valve, that safety device may become ineffective due to the high inlet water pressure.

This combination of circumstances can produce high inlet water pressure at a water heater tank that combines with thermal expansion pressure to create unsafe water pressures in the system. If we add to this list of water heater overpressure risks the chance that an upper-limit temperature control is damaged or tampered-with, severe overheating at a water heater tank and even a BLEVE explosion can can occur.

BLEVE explosions or boiling liquid vapor explosions can occur at both domestic water heaters (calorifiers or geysers) and at hot water heating boilers (hydronic heating systems). We discuss the role of pressure/temperature relief valves in protecting against these hazards at RELIEF VALVES - TP Valves on Boilers and at RELIEF VALVES - Water Heaters. As we further explain at RELIEF VALVES - Water Heaters, in some locations where hard water is found, an expansion control valve is also used to drain excess hot water tank pressure.

If the building water pressure gauge reading is ever found at 80 psi or higher, you will want to install a water pressure regulator at the point where water supply enters the building. Watts produces a Watts Governor 80™ used for this purpose, but other manufacturers also produce a wide variety of water pressure regulators. If your building already has a water pressure gauge installed, it may be defective or it may be set too high.

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 see RELIEF VALVES - TP Valves on Boilers and RELIEF VALVES - Water Heaters.

And as we discuss at WATER PRESSURE REDUCER / REGULATOR, too-high incoming water pressure at a building can cause both dangerous conditions (bursting water tanks, heaters, boilers, piping, lime-clogged relief valves), and costly building flooding and mold contamination. That article also describes solutions to high incoming water pressure.

The articles listed at WATER PRESSURE REDUCER / REGULATOR explain how to adjust a water pressure regulator:

Watch out: If the building water pressure gauge reading is ever found at 80 psi or higher, you will want to install a water pressure regulator at the point where water supply enters the building. Watts produces a Watts Governor 80™ used for this purpose, but other manufacturers also produce a wide variety of water pressure regulators. If your building already has a water pressure gauge installed, it may be defective or it may be set too high. If your static water pressure is too high on a municipal supply, see WATER PRESSURE REDUCER / REGULATOR. The articles listed just below discuss how water pressure reducers / pressure regulators work and how to adjust a water pressure regulator:

Watch out: If your well water pressure is too high, see WATER PUMP CONTROLS & SWITCHES and see WATER TANK SAFETY.

What is Pressure Reducing Valve Wire Draw and Why is it a Problem?

"Wire draw" problems occur in a diaphragm-type (residential) pressure reducing valve at low or intermittent water flow rates that happen to be close to the shut-off or "close" point of the pressure reducer, the valve mechanism becomes unstable and begins to "hunt" for the proper valve seat position.

You'll notice wire draw on a pressure reducer valve if you hear chattering or noise caused by this rapid cycling, almost vibration, at the valve seat at low water flow conditions.

The underlying cause of wire draw problems on pressure reducing or pressure regulating valves occurs because the valve, probably the wrong model for where it is being used, is forced to operate for long periods at low flow rates very close to the "close" position of the pressure regulating valve. Water flowing over the valve seat through this nearly-closed very small opening can wear a groove or depression in the seat.

As a result, water may flow through that little opening even when the valve has closed. The continued flow of water through this worn groove or depression continues to form and enlarge this "wire-shaped" slot in the pressure reducing valve seat.

Mysterious Temporary Over-Pressure Water Pressure in Buildings: BLEVE explosions, Building Floods

What happens when a pressure reducing valve is suffering from wire draw? When no plumbing fixtures are being operated in the building for a period of time, water pressure will slowly increase above the intended or regulated pressure. The result, if we're lucky, is a mysterious leakage from pressure relief valves such as found on water heaters or boilers in the building. In the worst case, an overpressure condition at a water heater or boiler might damage the equipment or even render it unsafe.

Watch out: For example, chronic leaks out of a pressure/temperature relief valve, combined with a water supply high in mineral content, can lead to eventual pressure-temperature valve clogging and failure to operate in an emergency overpressure or overheating condition, resulting in a BLEVE explosions or boiling liquid vapor explosion. Or less dramatic, building leaks that cause flooding can also lead to costly mold contamination.

Watts discusses the wire draw problem in their literature on water pressure reducing valves. Watts points out that selecting a pressure reducer control that is properly-sized for the building and the incoming water pressure will avoid wire-draw and the potentially catastrophic failures to which wire draw can lead. A smaller pressure reducer valve or a pressure reducer with a stainless steel valve seat to resist corrosion is likely to be better in this case.

Watts informs us that:

In general, the minimum flow through a water pressure reducing valve should be 10% to 15% of the maximum flow rate desired in the system. Also, water pressure reducing valves should be selected based on the flow and pressure ranges listed in the literature, not the size of the pipe to which they will be attached. You should select a regulator whose operating pressures fall within the middle of its rated range.

WATER PRESSURE REGULATOR ADJUSTMENT explains how to adjust this device.

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WATER PRESSURE & FLOW MEASUREMENT
  WATER PRESSURE VARIATION CAUSES
  WATER PRESSURE TOO HIGH: DANGERS
  Definition of Static Water Pressure
  Definition of Dynamic Water Pressure
  Measure Municipal Water Pressure
  Measure Pump & Well Water Pressure
  WATER FLOW RATE MEASUREMENT
  HOT WATER PRESSURE EXPANSION RATE

WATER PRESSURE GAUGES
WATER PRESSURE GAUGE ACCURACY
WATER PRESSURE LOSS DIAGNOSIS & REPAIR
WATER PRESSURE PROBLEM DIAGNOSIS TABLE

  WATER PRESSURE REDUCER / REGULATOR
    What's a Water Pressure Regulator?
    Direct-Acting Pressure Reducing Valves
    Regulate High Incoming Water Pressure
    Select Proper Pressure Reducing Valve
    Wire Draw Leaks at Pressure Reducers
    Parallel Pressure Reducing Valves
    Expansion tanks relieve high pressure
    WATER PRESSURE VARIATION CAUSES
    WATER PRESSURE REGULATOR ADJUSTMENT
    Water Pressure Regulator Test, Repair
  WATER PUMP PRESSURE CONTROL ADJUSTMENT
  Water Tank & Pump Costs
  WELL PIPING LEAK DIAGNOSIS

WATER PUMP SAFETY

WATER PUMP WONT STOP RUNNING

WATER PRESSURE LOSS DIAGNOSIS & REPAIR
WATER PRESSURE PROBLEM DIAGNOSIS TABLE

  • Watts, 815 Chestnut Street, North Andover, MA, USA 01845-6098, web search 09/18/2010 Watts Regulator Corporation, 815 Chestnut Street, North Andover, MA, USA 01845-6098, provides pressure and temperature relief valves, water pressure test gauges, water pressure regulators, backflow preventers, check valves, and other plumbing and heating controls and supplies. Website: http://www.watts.com/
    • Watts Backflow preventers - 978-688-1811
    • Watts Control valves - 713-943-0688 for example Watts pressure reducing valves, original source: http://www.watts.com/pages/learnAbout/reducingValves.asp?catId=64
    • Watts Drainage products - 828-288-2179
    • Watts Potable water PEX plumbing - 978-688-1811
    • Watts Water safety controls - 978-688-1811
    • Watts Water quality & conditioning products - 352-465-2000
  • Water pump and pressure tank repair diagnosis & cost an specific case offers an example of diagnosis of loss of water pressure, loss of water, and analyzes the actual repair cost
  • Water pressure tank failures & water pump short cycling diagnosis and repair
  • Engineering toolbox properties of water - http://www.engineeringtoolbox.com/water-thermal-properties-d_162.html editor.engineeringtoolbox@gmail.com web search 09/16/2010
  • SI Metric.co.uk provides tables and constants for the properties of water - web search 09/16/2010 original source: http://www.simetric.co.uk/si_water.htm
  • Wikipedia on the Density of water at 1 atmosphere, web search 09/16/2010, original source: http://en.wikipedia.org/wiki/Density
  • Life Expectancy of Water Pumps - Well Pumps: how long should a water pump last? What affects pump life?
  • Life Expectancy of Wells & Water Tanks how long should a water well and its components last?
  • Smart Tank, Installation Instructions [ copy on file as /water/Smart_Tank_Flexcon.pdf ] - , Flexcon Industries, 300 Pond St., Randolph MA 02368, www.flexconind.com, Tel: 800-527-0030 - web search 07/24/2010, original source: http://www.flexconind.com/pdf/st_install.pdf
  • Typical Shallow Well One Line Jet Pump Installation [ copy on file as /water/Jet_Pump_Grove_Elect_Jet_Pumps_1.pdf ] - , Grove Electric, G&G Electric & Plumbing, 1900 NE 78th St., Suite 101, Vancouver WA 98665 www.grovelectric.com - web search -7/15/2010 original source: http://www.groverelectric.com/howto/38_Typical%20Jet%20Pump%20Installation.pdf
  • Typical Deep Well Two Line Jet Pump Installation [ copy on file as /water/Jet_Pump_Grove_Elect.pdf ] - , Grove Electric, G&G Electric & Plumbing, 1900 NE 78th St., Suite 101, Vancouver WA 98665 www.grovelectric.com - web search -7/15/2010 original source: http://www.groverelectric.com/howto/38_Typical%20Jet%20Pump%20Installation.pdf
  • Water Fact Sheet #3, Using Low-Yielding Wells [ copy on file as /water/Low_Yield_Wells_Penn_State.pdf ] - , Penn State College of Agricultural Sciences, Cooperative Extension, School of Forest Resources, web search 07/24/2010, original source: http://pubs.cas.psu.edu/FreePubs/pdfs/XH0002.pdf
  • Water pump and pressure tank repair diagnosis & cost an specific case offers an example of diagnosis of loss of water pressure, loss of water, and analyzes the actual repair cost

Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair

  • Our recommended books about building & mechanical systems design, inspection, problem diagnosis, and repair, and about indoor environment and IAQ testing, diagnosis, and cleanup are at the InspectAPedia Bookstore. Also see our Book Reviews - InspectAPedia.
    • Home Reference Book - Carson Dunlop The Home Reference Book - the Encyclopedia of Homes, Carson Dunlop & Associates, Toronto, Ontario, 2010, $69.00 U.S., is available from Carson Dunlop, and from the InspectAPedia bookstore. The 2010 edition of the Home Reference Book is a bound volume of more than 450 illustrated pages that assist home inspectors and home owners in the inspection and detection of problems on buildings. The text is intended as a reference guide to help building owners operate and maintain their home effectively. InspectAPedia.com ® author/editor Daniel Friedman is a contributing author. Field inspection worksheets are included at the back of the volume.

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