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PLUMBING TOPICS OIL TANKS SEPTIC SYSTEMS WATER PRESSURE & FLOW MEASUREMENT Definition of Static Water Pressure Definition of Dynamic Water Pressure How to Measure Water Flow Rate in a Building WATER PRESSURE GAUGE ACCURACY WATER PRESSURE LOSS DIAGNOSIS GUIDE BAD MUNICIPAL WATER PRESSURE or FLOW BAD WELL WATER PRESSURE or FLOW Water Pressure Intermittent No Water Pressure Well Tank relation to Water Pressure Shaking the Water Tank? Water Pressure Tank Problems Water Pressure Tank Diagnosis Water pressure Later Returns "on its own" Water pipe clog diagnosis Water pipe clog repair guide Making the "right" repair Typical Water Tank & Pump Prices Typical Pressure Tank & Pump Prices WATER PRESSURE REGULATOR ADJUST What's a Water Pressure Regulator? Causes of Variation in Water Pressure Diagnose Poor Municipal Water Pressure Adjust Bad Pressure Regulator on Municipal Water WATER PRESSURE REPAIR GUIDE & COSTS Questions about lost water pressure Advice to a homeowner Adjusting Water Pump Pressure Control Right Repair to Pump & Tank? Well Pump & Tank Replacement Costs WATER PUMPS & WELL TANKS WATER PUMP CONTROLS & SWITCHES IDENTIFY WELL PUMP TANK COMPONENTS MAIN WATER SHUTOFF VALVE WATER PUMP ELECTRICAL SWITCHES WATER PUMP PRESSURE CONTROL WATER PUMP PRESSURE CONTROL ADJUSTMENT WATER PUMP PRESSURE CONTROL REPAIR WATER PUMP PRESSURE CONTROL REPLACE WATER PRESSURE REGULATOR ADJUST WATER PUMP RELAY SWITCH WATER TANK AIR VOLUME CONTROLS TANK AIR INLET VALVE TANK AIR VALVE REPAIRS WATER TANK PRESSURE GAUGE WATER TANK DRAIN VALVE WATER TANK RELIEF VALVE CHECK VALVES WATER FILTERS WATER PUMP TYPES & LIFE EXPECTANCY WATER PUMP & TANK SAFETY WATER SUPPLY & DRAIN PIPING WATER TANK TYPES: WATER, OIL, EXPANSION, ALL WATER TANK LIFE EXPECTANCY WATER TANK REPAIRS CONTROLS & SWITCHES on WATER TANKS INTERMITTENT CYCLING WATER PUMPS WATER TANK AIR, HOW TO ADD WATER TANK BLADDERS & CAPTIVE AIR WATER TANK REPLACEMENT WATER TANK BLADDER PRESSURE ADJUSTMENT WATER TANK PRESSURE CALCULATIONS WATER TANK SIZE & VOLUME WATER TANKS HOW THEY WORK WATER TESTING WATER TREATMENT EQUIPMENT CHOICES WELLS CISTERNS & SPRINGS WELL LIFE EXPECTANCY WELL PUMP TYPES & LIFE EXPECTANCY More Information InspectAPedia Blog - News Updates Air Conditioning & Heat Pumps Bookstore Electrical Environment Exteriors Heating Home Inspection Insulate Ventilate Interiors Mold Inspect/Test Plumbing Water Septic Roofing Structure Accuracy & Privacy Policies Contact Us |
This article describes how to measure water pressure and water flow in buildings in order to diagnose bad pressure or bad water flow. The process of water pressure problem diagnosis and the costs of the repair are explained. Readers whose building is served by a private pump and well system should see WATER PUMP PRESSURE CONTROL. 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. © 2009 Daniel Friedman, All Rights Reserved. Information Accuracy & Bias Pledge is at below-left. Use links at the left of each page to navigate this document or to view other topics at this website. Green links show where you are in our document or website. Causes of Variation in Building Water PressureThe water pressure regulator setting may not be the same as the water pressure you'll actually get in the building. Depending on the size of the building, its piping size and length of piping runs, and the number of fixtures and number of occupants (and similar variables) in a building, it is possible to draw water out of the building supply piping at such a high rate that the overall building water pressure drops considerably below the pressure setting at the water pressure regulator. With a municipal water supply the water pressure will vary depending on how many fixtures are being run, and also the municipal water system pressure may vary in the street as well. Water flow rate in a building also depends on the diameter, length, and number of bends or valves in the piping system. Clogged water pipes reduce water flow rate, not water pressure. With a private well and pump water supply, water pressure will also vary depending on the water pump on and off cycle and possibly on the ability of the well to deliver water. How to Measure Building Water Pressure: Static Building Water Pressure & Dynamic Water PressureDefinition of Static Water Pressure
Typically on a municipal water supply the static water pressure in the building will be 30-60 psi, depending only on the setting of the water pressure regulator - the regulator determines static water pressure in the building. On a private well and pump water supply system water pressure varies between 20-40 psi or 30-50 psi depending on the equipment installed and the pump pressure control switch settings. (See WATER PUMP PRESSURE CONTROL ADJUSTMENT). Our photo (left) shows a simple and inexpensive home-made water pressure measuring gauge that we attached to the cold water faucet for a washing machine hookup. Building suppliers also sell water pressure gauges with the same fittings to attach the gauge to a hose or faucet hookup (see our page top photo). To measure static water pressure, attach a pressure gauge anywhere in the building on water supply piping. Make sure that no plumbing fixtures are running, and if the building is served by a well and pump system, make sure that you have run water until the pump starts running, then turn water off. The pressure read on the gauge with all fixtures "off" is the maximum static water pressure at the building. Static municipal water pressure may vary at different times of the day depending on what pressure is being delivered by the municipal supplier. In some communities municipal water pressure varies little while in others the variation can be significant. Static well water pressure depends on the setting of the pump controls. Definition of Dynamic Water Pressure
On a municipal water supply system the dynamic water pressure and flow seen in a building will drop to a number lower than the static water pressure but will normally remain steady when you turn on one or more plumbing fixtures. On a pump and well water supply system the dynamic water pressure and flow seen in the building will drop to a lower number than the static water pressure, and will also vary as the pump cycles on and off. Example of variation in building water pressure:
On a pump and well water supply system when multiple plumbing fixtures are operating, the dynamic water pressure will fall to a lower number and will hover there once the quantity of water being drawn causes the pump to turn on and stay on - that is, when you are running water fast enough that the pump cannot "get ahead" of the water draw out rate. How to Measure Water Flow Rate in a Building
For example, if the time required to fill the five gallon bucket is one minute, then the water flow rate at this plumbing fixture is 5-gallons per minute or 5 gpm. One can purchase "flow meters" that connect to various plumbing fixtures to pretend to make this measurement, but remember that we are measuring the flow rate at the particular fixture - to obtain a number that does not necessarily describe the water flow rate capability of the water supply system. The measurement of water flow rate at a particular plumbing fixture does not accurately measure the true water flow rate of the plumbing system because:
On a pump and well system when we turned on water at just the kitchen sink (Dynamic Water Pressure photo above) the flow rate dropped slowly until the pump turned on. Then the water pressure rose slowly until the pump turned off. Water pressure varied between 38 psi (pump off) and 25 psi (pump on). When we turned on water at a bath tub faucet (photo just above) water pressure dropped to about 28 psi and stayed there as the well pump ran continuously, delivering water to the building at that rate. You can see our pressure gauge reading 28 psi. How to Fix Bad Water Pressure or Bad Water or Well Flow RatesOur water pressure and flow diagnosis and repair guide starts at WATER PRESSURE LOSS DIAGNOSIS GUIDE. If your dynamic water pressure is too low on a municipal water supply system you can boost building water pressure by installing a pressure booster pump and water tank. See WATER PRESSURE REGULATOR ADJUST and see PUMP, WATER PRESSURE BOOSTER. If your dynamic water pressure is too low on a private pump and well system you may be able to boost water pressure by adjusting the pump pressure control switch. See WATER PUMP PRESSURE CONTROL ADJUSTMENT. ... Technical Reviewers & References
Use links just below or at the left of each page to navigate this document or to view other topics at this website. Green links show where you are in our document or website. PLUMBING TOPICS | ||||||
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11/03/2009 - 09/15/2006 - InspectAPedia.com/water/Water_Pressure_Measure.htm - © 2009 - 1988 Copyright Daniel Friedman All Rights Reserved - InspectAPedia® is a Registered U.S. Trademark