The pressure from the street to your home is not constant; it fluctuates. Often the pressure will rise substantially at night when water demand in the neighborhood is at its lowest point. Maintaining a steady water pressure throughout your plumbing system is important. In fact, the pressure reducing valve (also called a pressure regulator) may be the most important single factor in your entire plumbing system.
Every faucet, angle stop, water heater, water closet, dishwasher, washing machine and hose bib in your home may suffer excessive wear and begin to malfunction if the pressure is not kept in check. If your home has reading of over 75 psi (pounds per square inch), it is not being controlled by a working pressure regulator; either one is not present, has been bypassed, or has failed. The only exception to this rule is in systems which use a multi-range pressure regulator to accommodate landscaping demands. In the unlikely event that someone has used one of these specialized pressure regulators on a house system, the pressure should be adjusted to below 75 psi. If the pressure reducing valve cannot be set below 75 psi then it should be replaced or repaired.
In order to adjust the pressure on your water pressure regulator you must have a pressure gauge attached downstream, i.e. after the regulator. Often you will find a hose bib just above the regulator coming into the house. Just be sure the hose bib is located after the regulator on the line going into the house. The water pressure gauges have a hose bib thread on a swivel adapter to attach them to a bib. House pressure should be between 50 and 75 psi.
Adjusting the pressure on a working regulator is not difficult. Instructions here are for a Zurn/Wilkins #600 but should work for most regulators, when in doubt check the manual or look up the manufacturer online for the product specifications. Some regulators use arrows on the cap assembly to indicate which way to turn the cap to increase or decrease the pressure. Keep in mind that a nonfunctioning regulator might start leaking if you try to adjust it so have a qualified plumber waiting in the wings if a problem develops. On the Wilkins #600, turn the adjustment bolt clockwise to raise the pressure or counterclockwise to lower it; be sure to loosen the locknut which holds the adjustment bolt in place. Keep an eye on the pressure gauge during this process, or if the gauge is somewhere else have someone watch it for you. Once you have obtained the correct pressure then secure the locknut.
There are several issues that can indicate a problem with your water pressure: valve noise, low flow from fixtures, unsteady flow, and creeping pressure build up. We will deal with each one of these in turn.
Your valve might hum, whistle or chatter. Water travelling at high speeds is the usual cause of vibration that leads to hum or whistle. If you are experiencing hum or whistle it is likely that either your pipes are too small or you have an undersized valve or two in the line; have a plumber check this out for you.
If the seat washer is worn or the seal ring is loose inside the regulator, this may cause chatter. Many regulators have repair kits available to deal with worn seat washers or seal rings but do take mechanical aptitude to install. Repair kits do not always work because the body of the unit may have worn due to water passage over time-think the Grand Canyon in miniature. You may spend about one-third of the cost of a new regulator on a repair kit and it might not do the trick. If you call a plumber they will probably replace the regulator because they understand about water wear. Most plumbers warranty their parts and labor. Be sure to ask.
Low flow can be caused by a clogged screen in your regulator, pipe that is too small in the home, or excessive demand by appliances. It also could be a combination of all three. Checking the troubleshooting guide for your regulator should give you a clue on how to clean the screen. Again, keep in mind that water wear could make the regulator impossible to take apart without a problem.
Unsteady flow is often caused by low pressure in the main supply from the street due to excessive demand at peak hours of the day. It can also be caused by appliances such as dishwashers and washing machines being used at the same time. If the pressure from the main fluctuates this is a problem brought on by your water department; there may be little that can be done about this. If, on the other hand, it is due to small house service lines then you can have the size of the lines increased. Before you consider that expense, though, try increasing the pressure at the regulator.
Creeping pressure build up in the house supply can be caused by thermal expansion. It may happen each time your water heater runs. A thermal expansion tank at the water heater should help; it will not prevent the pressure rise but it should limit the rise to a reasonable level. This small tank absorbs excess pressure by cushioning it. The burst of water pressure presses against the diaphragm in the tank; the diaphragm is forced down against compressed air and moves toward the base of the tank. This motion of the diaphragm against the compressed air relieves the shock of the excess pressure. In many areas thermal expansion tanks should be used to protect against excessive pressure build up. On the other hand, the regulator itself may be the problem because of worn or cut O-rings or seals. It might have foreign matter inside so you can try to flush it by opening at least two outlets to full volume for up to 5 minutes. There may be something stuck on the seating face of the seal ring that this may dislodge. For worn parts a repair kit might do the trick but keep in mind that the body of the unit might also be worn beyond repair. Replacing the unit might be the best bet.
Solving your problem could be as simple as turning the bolt on your regulator. It could be as complicated as increasing the line size throughout part or your entire home. Letting the situation continue will almost certainly add to your problems. Keep an eye on your water pressure. Your checkbook will love you for it.