Common Causes of Low Water Pressure


Low water pressure is one of the most predominant issues that plague almost all homes at one point or another. Whether you are a new or experienced homeowner, chances are that you will most likely struggle with this tricky phenomenon. Adequate and consistent water pressure is a crucial factor in the quality of living that we enjoy on a daily basis. Everyday activities, such as washing dishes, doing laundry, cooking, and showering can become burdensome tasks if the water pressure in our household piping system is below standard.

In addition to the inconveniences associated with low water pressures, finding its root cause can sometimes be equally frustrating. While some of the causes are relatively straightforward and easy to rectify, others are more complex and may be indicative of more severe issues; thus requiring the services of a licensed professional.

Pressure vs. Flow

Before we can investigate the causes of low water pressure, it is essential to first understand the difference between two generally misunderstood terms: pressure and flow. One of the most common misconceptions, even among experienced plumbers, is that water pressure can be increased by using a smaller diameter pipe. This, however, is not the case.

Water pressure is used to describe the force responsible for pushing or driving the water through the plumbing system. In households that receive water from public utilities, the water pressure is controlled by the municipal water system; for homes with private well systems, this pressure is governed by the quality and configuration of the well pump. Water pressure is measured in terms of force per unit area or pounds per square inch (psi). In most households, acceptable water pressures typically range between 40psi and 60psi. This parameter is usually measured with a pressure gauge or pressure sensor (transducer) screwed into a fitting on the pipe.

Flow rate, on the other hand, is defined as the volume of water passing through a pipe or fixture within a fixed amount of time. The higher the flow rate through a fixed opening, the greater the velocity of the water through the opening. Flow rate is expressed as volume per unit time, typically cubic feet per second.

While these two terms may seem similar, they are independent of each other. While pressure refers to the force required to move water from one point to another, flow refers to the amount of water coming out of the pipe. They are two distinct parameters that are adjusted in different ways. Flow can be altered by adjusting the shape or size of the opening at the end of the pipe, for example, changing the type of showerhead or faucet aerator. Whereas, water pressure can be altered by changing the diameter or texture of the piping, using different pump/regulator settings, or varying the elevation of water passing through the line. Bigger and smoother pipes provide less frictional resistance and, therefore, results in a higher, more consistent pressure through the pipeline. Smaller pipes, while they can increase the velocity of the water flow, tend to reduce water pressure due to increased friction.

Common Causes of Low Water Pressure

The causes of low water pressure vary widely; however, knowing is half the battle. Understanding the reasons behind pressure fluctuations is crucial in determining the appropriate and most effective plumbing solution. Addressing these problems in the early stages of development can also help minimize inconvenience and prevent the onset of more severe issues. Here, we present the seven most common causes of low water pressure in both municipal and well water household plumbing systems.

  • Clogged Pipes and Fixtures – Objects like dust, dirt, and grease can make its way into the plumbing, accumulating at various sections of the piping. Hard water (i.e., water with high mineral content) can also leave behind residue, which can adhere to the walls of the piping, resulting in the buildup of mineral deposits. This debris reduces the effective diameter of piping while obstructing flow; thus resulting in increased frictional losses and decreased water pressure.

In homes supplied with well water systems, a common cause of low pressure is clogging of the sediment filter. In some cases, the pressure switch which activates and deactivates the pump at the required pressure setting may also become blocked due to sediment accumulation in the pressure sensor tube. As a result, the pump may fail to operate at the correct water pressure.

If the problem is limited to a particular faucet, the problem may be the aerator, in which case, the issue is restricted flow as opposed to low pressure. Normal flow can be restored by simply removing the aerator and cleaning it with a brush. If the pressure is observed to be inconsistent throughout the household, a licensed plumber should be contacted to assess the situation.

  • Corroded Pipes – Corrosion is a destructive chemical or electrochemical reaction which causes the walls of steel pipes to dissolve or deteriorate. This natural process occurs when steel reacts with the surrounding air and water. During corrosion, the walls of the steel pipe dissolve, while corrosion products are formed in its place. These products, commonly known as rust, occupy a significantly greater volume than the steel, resulting in a buildup which reduces the effective diameter of the pipe; thus hampering the delivery of sufficient water pressure.

Corrosion is a relatively slow process. It can proceed for many years before water pressure issues are evident. Therefore, low water pressures due to corrosion are fairly common in older houses consisting of cast iron or aging galvanized steel plumbing. If left untreated, corrosion can eventually penetrate the piping walls, leading to cracks, leaks, and rupture; all of which can also cause the pressure to drop significantly.

Depending on the severity of the corrosion, the solution to corroded piping usually entails re-piping of the system with plumbing manufactured from corrosion resistant material (copper, plastic, etc.). This issue is, therefore, one that requires the services of a licensed plumbing professional.

  • Faulty Pressure Regulator

Low water pressures may also be caused by a defective pressure regulator (this issue, of course, is only applicable to homes where these devices are installed). Pressure regulators are essentially control valves that adjust the input pressure to safe levels. This ensures that damage to the piping system is minimized during pressure fluctuations. Unlike clogged piping or corrosion, where pressure reduction is a gradual process, low pressures due to failed regulators usually occur suddenly. Pressure regulators fail due to several reasons; however, wear due to consistent operation over years of service is most common. In well systems, pressure regulators are also susceptible to fouling from sedimentation.

Pressure regulators issues can be rectified by installing a replacement device of the same make and model. This operation requires some technical proficiency; therefore, like most plumbing repairs, it is best to contact a licensed professional.

  • Shutoff Valve Issues

Shutoff valves, as their name implies, are valves that are used to restrict or allow the flow of water into the household. The main shutoff valve is usually located inside the house, near to where the supply line enters the property. In some cases, the main shutoff valve may also be situated outdoors.

Although it may seem obvious, low pressures may be caused by a partially open shutoff valve. Partially opened valves usually occur after repair or maintenance operations have been performed on the system. This reduces the area which the water is allowed to traverse; thus, restricting flow and lowering output pressures.

If the valve is a gate valve (indicated by a wheel-like handle), ensure that the handle is rotated all the way in the clockwise direction. Ball valves, or quarter turn valves, consists of a lever-type handle. This valve is fully opened when the handle is parallel to the direction of the pipe. It is important to ensure that excessive force is not applied to the lever to minimize the risk of damage. If the valve is contaminated with debris, gently working the valve back and forth can help to loosen sediments, and achieve full water pressure.

  • Insufficiently Sized Main Supply Line

As mentioned previously, the notion that smaller diameter pipes can increase water pressure is a common misconception. In fact, the smaller the pipe diameter, the higher the frictional forces in the pipe, and the greater the pressure drop as the water is pumped through the line. For supply lines located within the property boundary, a licensed plumbing contractor can verify the sizing of the pipe and its connections.

If the problem persists, then it is possible that the problem may lie with the municipal water supply infrastructure. This can be verified by confirming if other residents in the area are experiencing the same problem. Issues with the city’s water supply usually occur after mainline maintenance and repairs. In this case, the matter should be reported to the local municipal supply company for further action.

  • Pressure Tank Problems

Faulty pressure tanks are a common cause of water pressure issues in well water systems. The pressure tank is an essential component in pumping systems. These devices help to ensure that consistent pressure is delivered to the home without continuously running the well pump.

There are several types of pressure tanks, each with a different operating mechanism. The most common type of pressure tank consists of an inflated air bladder, or diaphragm, which imposes pressure on the well water contained in the tank. When the water level in the tank drops due to usage, the pressure in the tank reduces, activating the pump to replenish the water and pressure inside the tank.

Under-inflated bladders or diaphragms can ultimately result in low water pressure outputs from the tank. As with many plumbing hardware issues, this problem is best looked at by a professional. The air valve located at the top of the pressure tank allows pressure measurements to be verified using a standard air gauge. Depending on the reading, plumbing contractors determine the appropriate repairs or adjustments to be made.

  • Failing Well Pump

Another common cause for low water pressure, particularly in well water systems, is a faulty well pump. While pumps are relatively durable, they consist of several high-velocity moving components, making them susceptible to several types of failure such as mechanical breakdown, cavitation, and erosion.

In addition to reduced water pressure, some of the signs of pumps failure include odd, loud noises, and unusually high electricity consumption. Water-logged pressure tanks, i.e., too much water in comparison to air, can also contribute to premature pump failure as continuous on and off cycling can accelerate mechanical wear and tear. Also, while submersible water pumps can last a number of years, poor well water quality can also shorten the pump’s lifespan. The inner workings of pumping systems can be complicated, and their repair is beyond the scope of most homeowners. A plumbing professional should, therefore, be contacted immediately to diagnose and repair any pump-related problems.

In Summary

Inadequate water pressure can be attributed to a wide array of factors. While some issues, such as faulty or clogged fixtures are relatively easy to identify and can be addressed by novice homeowners, other causes, such as corrosion and hardware issues (pressure tank, valves, pumps) need to be addressed by a licensed professional. Regardless of the reason for inconsistent pressure, proper diagnosis and swift repair can help minimize inconvenience and minimize piping infrastructure and pumping equipment damage.