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What is water pressure? What is a Water Pressure Regulator? What is wrong with high water pressure? Does high water pressure cause “water hammer”? What is the difference in water flow from a fixture when the pressure is at 100 psi vs. a pressure of 50 psi? Where are Water Pressure Regulators most commonly used? Why do we now call Regulators “Primary Conservation Controls”? How do Regulators save water? How much does a typical family of four use? How do Regulators affect the waste water system? How do Water Pressure Regulators save on energy? How do these savings benefit the water and energy utilities? How do Regulators save on maintenance? Do codes require Water Pressure Reducing Valves? How long will a Regulator last? If I install a Pressure Regulator, what savings can I expect? Should we consider using other water and energy conservation devices? Do flow-restricting devices actually save water? What are some tips the user can employ to save water and energy? How do I know if I have high water pressure? How can I get a Water Pressure Regulator installed? |
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What is water pressure? Pressure is a force per unit area and is usually measured in pounds
per square inch (PSI or pounds/in2). You are probably
already familiar with measuring pressure. Every time you weigh
yourself, you are measuring the pressure exerted by your body on the
scales.
The area of the bottom of the container is found by
multiplying the length of two of the sides.
0.43 pounds = 0.43 pounds/in2 = 0.43 PSI A dull knife slicing through bread is a perhaps more familiar example of pressure. Once the knife has exerted a certain amount of pressure on the bread, the bread will break apart. Once again, think of pressure as a force per unit area. If you are using a dull knife, then the area of the knife blade which presses against the bread is large. You will have to use a large amount of force to cut the bread since the surface of the knife is so big. But if you sharpen the knife, the smaller blade surface will exert the required amount of pressure on the bread when you apply less force. So, in order to increase the pressure, you either need to increase the force being applied or decrease the area which the force is being applied to. There are two types of water pressure: static and dynamic. Static is pressure supplied by the mass of water per unit area and dynamic is pressure supplied by mass combined with the energy of motion. Static Pressure There are two components of pressure: static and dynamic pressure. The water pressing down on the bottom of a container is an example of static pressure. Static pressure is pressure applied by non-moving water as a result of gravity. Gravity pushes the still water down and applies pressure on the bottom of the container. Static pressure is a form of potential energy. Potential
energy is energy which is not currently causing any sort of motion, but
which has the potential to cause motion. A ball sitting at the top
of a hill is another example of potential energy. The ball is sitting
still, but if it started to roll, it would go all the way to the bottom
of the hill without anyone pushing it.
A reservoir is also an example of potential energy.
The water is sitting still in the reservoir, exerting pressure on the
reservoir bottom and on the dam.
Kinetic energy is the energy of motion. Once a
ball begins rolling down a hill, it is moving and has kinetic energy.
Similarly, if the floodgate in a reservoir is opened, then the water's
energy becomes kinetic energy and gushes out of the reservoir.
Static pressure is what causes water to seek its own
level. When you pour water into a dish, the water quickly
spreads out to cover the entire bottom of the container in a flat layer.
Any high points in the water are pushed down by gravity until they are
level with the rest of the water.
Water in different parts of the pipe will have different pressures. This difference in pressure is measured by differential pressure meters. By reading the pressure at two points in a pipe and taking into account the resistance of the pipes, the flow rate of the water can be determined. Resistance, or friction, in pipes is caused when water rubs against the edge of the pipe and slows down. In a hydraulic system, the pressure of the water at one point against the water at another point causes the water to flow. If a pressure gauge on a pipe reads 40 PSI, that means that the water is pushing against the nearby water with 40 pounds of pressure for every square inch. If the pressure in the pipe was greater, the water would push harder against the surrounding water and cause the water to flow faster. When a fixture in a home is opened and water flows from it, it is because the water is "pushed." This "push" is pressure. The speed at which water flows from the opened outlet depends on the amount of "push" or pressure which exists at that time in the system. In short, the higher the pressure, the stronger the "push" behind the water. What is a Water Pressure Regulator? Also called water pressure reducing valves, they are compact, inexpensive devices that perform two functions: (1) they automatically reduce the high incoming water pressure from the city mains to provide a lower, more functional pressure for distribution in the home; (2) they "regulate" by maintaining a set pressure in the home usually 50 psi -- thereby insuring that the home piping and appliances operate under a safe, more moderate, but satisfactory pressure. What is wrong with high water pressure? High water pressure, which is generally considered anything above 60 lbs., has some advantage, such as in firefighting systems. However, in the home plumbing system, it can be damaging because water, with a strong "push" behind it, can erode or wear away many materials and cause water heaters to leak, banging water pipes, dripping faucets, excessive dishwasher and clothes washer noise and breakdown, and leaking water pipes. Therefore, water flowing at a rate in excess of that necessary to satisfy normal fixture or appliance demands becomes damaging, wasteful and reduces the life expectancy of equipment in the system. But, most important to the average homeowner is that high water pressure can add to the cost of water, energy and waste water bills. 3 Leaking water heater Banging water pipes Dripping faucets Dishwasher breakdown Does high water pressure cause “water hammer”? Yes. Water hammer is simply the noise generated by the shocks of high-speed water flowing in a pipe when a fixture is suddenly closed. This abrupt stoppage causes a “bounceback” of the water and is called water hammer, causing banging pipes, noisy systems and damage to appliances. It might be compared to driving your car at slow speed into a wall where the effect is negligible. However, if you drove the car at a much higher speed, the impact would be greater and, consequently, so would the bounceback or shock. Another description of the water hammer effect of high water pressure can be easily demonstrated. First, walk around a sharp corner and then run around the same corner. We can equate walking around the corner to a lower, more functional, controlled water pressure. However, when you run around the corner, the momentum forces your body to swing in a wider, uncontrolled arc. This principles based on the fact that moving objects, and this includes water, tend to move in a straight line. They resist changes in direction. Therefore, in a home where the piping has many changes in direction, water hammer shock can be limited by reducing the water pressure. 5 What is the difference in water flow from a fixture when the pressure is at 100 psi vs. a pressure of 50 psi? Reducing the pressure from 100 psi to 50 psi will result in a saving of approximately 1/3 because 1/3 less water flows at this lower pressure. Remember, there is more "push" behind the water at 100 psi than at 50 psi and most of this water is wasted. Note the illustration where almost twice as much water flows at 150 psi than 50 psi, most of which is wasted. A moderate savings would result if your supply pressure was reduced to 65 psi However, even at this lower pressure, savings with a regulator would be 20%. 5 150psi 100psi 50psi 30 65psi 36 80psi 40 45 56 6 gals 10 gals 15 gals 26 gals Supply Pressure Water Flow in Gallons Faucet with 10 minutes running time. Fast motions exert greater forces. Where are Water Pressure Regulators most commonly used? Water pressure regulators are commonly installed at the meter in residential, commercial and industrial buildings. This location is desirable because it then controls the water pressure flowing to all appliances and outlets within the building and provides an inexpensive means of supplying lower, more functional water pressure to outlets and appliances. Why do we now call Regulators “Primary Conservation Controls”? Most people have considered regulators as pressure controls because, as described in the foregoing, they are used to protect appliances and piping from the effects of high water pressure. However, because of water and energy shortage and cost problems, regulators have become increasingly more important because they automatically provide the advantage of conserving water and energy. How do Regulators save water? As mentioned before, 1/3 less water flows at 50 psi than at 100 psi Therefore, when you reduce the _________ main pressure to a more moderate pressure of 50 psi, you can look forward to conserving up to 1/3, or more, of the water previously consumed. How much does a typical family of four use? A typical family of four uses an average of 255 gallons of water each day. This is broken down by: dishwashing - 15 gallons; cooking/drinking - 12 gallons; utility sink - 5 gallons laundry - 35 gallons; bathing - 80 gallons; bathroom sink - 8 gallons; toilet - 100 gallons. When you multiply this by a year, typical family usage totals 93,000 gallons of water. Your family particularly if it includes teenagers, would undoubtedly use more than the above averages. How do Regulators affect the waste water system? When we can save 1/3 of the water previously consumed, this also represents a similar saving of water which will not be going into the sewer system where it has to be treated. Water does not evaporate after we use it and it has to be piped to the wastewater system. Many sewer bill taxes or surcharges are based on the amount of water you use, with the assumption that this water is going into the wastewater system. This is billed to you as a sewer surcharge and, in many cases, the sewer tax can equal the water cost. Therefore, when pressure regulators save 1/3 of the metered water, they also contribute to saving up to 1/3 of the wastewater load and this is extremely important because it benefits both the user, by a lower sewer bill, and the community, as this is water they do not have to treat. How do Water Pressure Regulators save on energy? The Environmental Protection Agency estimates that 30% of the water used in households is heated. In order to heat this water, it takes energy. Logically, therefore, if a pressure regulator can reduce consumption by 1/3, we automatically cut down on the amount of hot water we're using in lavatories and showers and, therefore, it follows that we automatically reduce the amount of energy required to heat that load. Thus, it can be easily seen that water conservation has a direct relationship to energy conservation. An average shower, for example, costs approximately 17 cents in energy and a shave with the faucet running cost 10 cents in energy. How do these savings benefit the water and energy utilities? A high rise office building in Chicago was designed using water conservation products which resulted in savings of more than 3,000,000 gallons of water per year. This is significant in that the municipal water utility did not have to pump that extra gallonage, the water purification plant didn't have to treat it, the building itself saved on pumping of 3,000,000 gallons, and there must have been significant savings in energy by conserving hot water. Also, there were further savings by the fact that 3,000,000 gallons of water, or the normal portion thereof, did not have to be distributed to the wastewater system and consequently the water treatment plant did not have to retreat this water. The heating of water takes energy and it should also be remembered that "pumping" water from one place to another also requires a considerable amount of energy. How do Regulators save on maintenance? We have previously described the effects of high water pressure on piping and appliances. By having these appliances work under a lower pressure, their life expectancy will be much longer. Use of lower pressure will also cut down on service calls caused by problems with dish washers and clothes washers, leaky water heaters, leaking water pipes and the potential water damage which could result. Do codes require Water Pressure Reducing Valves? Yes. They are required by the Federal Housing Administration, the regional plumbing codes such as IAPMO, Southern Building Code, and BOCA, and numerous city and state codes. The requirement is that whenever the city main water pressure exceeds 80 psi, a regulator must be installed. However because of the recently acknowledged advantages of regulators conservation wise, regulators could be economically installed even where supply pressures are in the vicinity of 60 psi because of the water and energy saving benefits they can provide. How long will a Regulator last? Regulators have been described as "life-of-mortgage" products, because historically a malfunctioning pressure regulator is not replaced but simply cleaned or repaired via an inexpensive service kit. Design wise, it is similar to the kitchen faucet in that dirt or foreign matter on the seating area can cause problems. Actually it is no more difficult to repair a regulator than it is to fix the kitchen faucet. 13 Leaking water pipes Washing machine breakdown Water Pressure Regulator Seating area easily accessible. As easily cleaned or serviced as a kitchen faucet. Regulators are designed to be maintained with the minimum of care. Should we consider using other water and energy conservation devices? Certainly. The water pressure regulator we're talking about today is the hub of a conservation program; but you should also consider other flow control devices, low-flush toilets, improved water heating equipment and better disciplined usage habits. However, if none of these other devices were installed, the water pressure regulator would still serve to contribute important and significant savings in energy and water. Do flow-restricting devices actually save water? Yes, and they can effectively be installed on showerheads, fixtures and tankless heaters in boilers. Many showerheads, for example, supply water at a rate of 6 gpm. Applying a 3 gallon per minute flow restrictor will cut the flow in half providing savings in water and energy. It should be remembered however that their capacity is based on a "fixed" supply pressure like 50 psi and operating under a higher pressure will permit greater flow. That's why we say a water regulator is the "hub" of a program because it maintains a constant pressure throughout the home, thereby even improving the performance of flow-restricting devices. 20 What are some tips the user can employ to save water and energy? 1. Put a stopper in your sink or use a dishpan when you wash dishes. Washing with running water uses 30 gallons per meal. 2. Keep a bottle of drinking water in the refrigerator -- running the water from the faucet until cold will waste a gallon. 3. Wait until you have a full nine-pound wash before you run your washing machine. The average machine uses 50 gallons per load. 4. Turn the hot water off while you shave, and turn the cold water off while you brush your teeth. Shaving with a running faucet uses about 20 gallons. 5. Take showers instead of baths. The usual bath requires 36 gallons, the usual shower, only 25. Ten gallons is enough for a shower if you turn it off while you lather. 6. Don't use the toilet bowl to dispose of cigarette ashes, facial tissues, and other materials. A normal flush requires 5 - 8 gallons. 7. Use dishwasher only when completely full. 8. Fix dripping faucets promptly. Nearly two gallons can be wasted per day of dripping. 9. Running toilets can waste four gallons per hour. Keep them in good repair. 10. THINK before you turn on the tap. NOTE: Tips provided through courtesy of Plumbing Manufactures Institute. 17 Based on 50 psi supply pressure 18 How do I know if I have high water pressure? A rule of thumb is: If you hear banging pipes in your home or observe water splashing in your sink, you probably have excessive pressure. However, for a precise reading, your local plumbing contractor or utility can test your pressure with a gauge. 23 How can I get a Water Pressure Regulator installed? The easiest way would be to call your local qualified plumbing contractor who can provide you with an estimate and also advise of the various type regulators available and the one best suited for your home. Although regulators are fairly simple to install and could be a do-it-yourself project, there are some laws which provide that only a licensed plumbing contractor be permitted to work on the home potable drinking water system for health and safety purposes. Maintain minimum operating pressure of 35 pounds per squire inch (psi) throughout the water distribution system. * Maintain minimum operating pressure of 20 psi under fire flow conditions. Where the water pressure within a building exceeds 80 psi, an approved water pressure reducing valve or regulator must be installed. The pressure reducing valve should be capable of limiting the water pressure in the building water distribution piping to 80 psi or less. What are the normal flow rates from a water service? Most water services provide about 20 gallons of water per minute. However, the flow rates from faucets can vary significantly. Bathtub faucets and outside hose spigots usually have flow rates of 7 to 10 gallons per minute. Kitchen and bathroom faucets, showers and toilets usually have flow rates of about 3 gallons per minute. What is considered normal water pressure? There really is no such thing as "normal" water pressure. Since water pressure is influenced by the elevation of the reservoir that serves your neighborhood versus the elevation of your water meter, water pressure varies from property to property. Water pressure in the District typically ranges from 45 - 125 psi; however, typical residential systems are designed to function best under a pressure of 40 - 60 psi. If the water pressure entering you home exceed this level, you should install a pressure regulator in the line to reduce the pressure to an acceptable range. This protects your equipment and piping in your home from damage from excess force exerted by the water. Symptoms of high pressure include "clanging" or "rattling" of pipes that occur when a faucet, dishwasher, or washing machine shuts off; water heater pressure relief valve malfunctions, and reoccurring leaks. The symptom of low pressure is typically a noticeable reduction of flow. What is a Pressure Regulating Valve? picture of pressure regulating valve, or PRV Pressure regulating Valves (PRVs) are a type of valve installed in a plumbing system to regulate water pressure. PRVs are designed to reduce too-high incoming pressure from water mains to a lower, more functional water pressure for distribution throughout the property. Why would you want to reduce water pressure? High water pressure can damage a property's plumbing system. The increased force of the water can erode or wear away system components more quickly than at normal pressures, and can cause leaks in water heaters or other appliances and pipes. Installing PRVs can reduce friction and help prolong the life expectancy of plumbing fixtures, appliances, and irrigation systems. PRVs are also a water conservation tool, since higher water pressure equals higher water use during everyday activities (showering, hand washing, lawn watering) and especially when there is a leak. How do I find out my home's water pressure? When are PRVs required? State________ Code requires the installation of a PRV on properties with pressure greater than 65 pounds per square inch (psi). For most purposes 50 psi water pressure is adequate. Most residential PRVs have an operating range between 25-75 psi, and are preset at the factory at about 45-50 psi. Where is the PRV installed? Here are further guidelines. |
