Low water pressure in the house is usually due to low flow of water at the main source.
Water comes out of a pipe, nozzle, or showerhead with high velocity, but in low volume due to it being spread over a wide area.
The more quickly water flows through an opening under any kind of pressure (measured as PSI), the less area the water spreads out over, and the more it spreads out over, the lower the velocity.
In this article, we will discuss the most common causes of low water pressure in a house.
What Causes Low Flow At Main Source?
Water pressure is measured as pounds per square inch (PSI). If water is running through a pipe under 100 PSI, then it can push with 100lbs of force per square inch.
If you’re running water with 30 PSI, then it can push with 30 lbs of force per square inch.
People often measure the amount of flow as gallons per minute (GPM). If your water meter is marked with a GPM dial, then turn the handle until the needle lines up exactly with those marks on the dial.
If your water pressure is 80 PSI and your flow rate is 30 GPM, it means that 1 minute of time you can push up to 240 lbs of force through the pipe. This does not mean to press down on the handle for exactly one minute, but if you were to block or close off the end of the pipe at the faucet, then the water would stop flowing because it has reached the end of the pipe.
If your water pressure is 80 PSI and your flow rate is 30 GPM, then you have enough force to push through a pipe that’s two inches in diameter or smaller. You can also think of this as saying that if you had a 30 GPM flow rate, then you’d need to have a pipe with an internal diameter of less than two inches.
This is why water pressure goes down in the whole house; it spreads out over more area (makes for longer plumbing lines), and since it can’t go faster through each opening, the decreased velocity makes the pressure decrease.
3 Main Reasons For Low Water Pressure
The three major reasons for low water pressure are: high friction loss, backflow, and high head. If you have symptoms that indicate any one of these problems, consult your plumber to see what should be done. Let’s go over these causes one by one.
High Friction Loss
This includes loss due to valves, fittings, and the actual line itself. Even though water is incompressible (meaning you can’t squeeze it out of a pipe), the velocity of the water through the line does not remain constant as it has to change direction at each fitting, causing the velocity to decrease each time. This causes a “pressure drop”.
If there’s something between the water source and the area where you want it, such as an unopened valve or faucet closed too tightly, it can cause some of the pressure to remain behind in the line. This makes it harder for the water to flow out of that area, which causes low pressure.
Head is just another term for altitude. If you are very high up off the ground, gravity won’t pull on your water pipes as much since they’re not as long. Since there’s less pressure due to gravity pulling down, the velocity of the water is higher because there’s actually more force behind it. This causes high pressure in the lines.
How to Solve Low Water Pressure In The Whole House?
It’s very important to call a plumber right away if you experience low water pressure. Different reasons for low flow can cause different kinds of damage, and it’s best to let a pro check out what the problem is and how to solve it.
If you’re having problems with your shower or tub faucet, then there are some things you can try to fix it yourself, such as:
- Tighten all pipe fittings. You can usually do this by hand or with a pair of adjustable pliers, but make sure you only tighten the fittings and not strip them out; they’re made for low pressure and aren’t designed to withstand much force.
- Check for leaks and/or loose pipes. Tighten them if necessary, and replace any parts that are worn out.
- Put a short aerator on all your faucets. This will increase the water pressure inside the building because it increases the velocity of what’s coming out of the faucet.
- Call a plumber if these steps don’t work. If the problem is simply that your flow rate is too low, you can install an efficient water filtration device on all of your faucets to increase the pressure without increasing the velocity. This way, you won’t have to worry about ruining your plumbing or water heaters with the increased pressure.
How To Solve Low Water Pressure For Dishwashers?
A dishwasher works the same way as a sink faucet does, so you can try using an aerator to increase your flow rate. If this doesn’t work, it’s probably because of either high back-pressure or high friction loss.
If your dishwasher isn’t getting enough water, there might be a clog in the hose that carries it back to the sink or in another section of the line. It’s also possible that one of the pumps got worn out and is no longer pumping water into the dishwasher when it should. In these cases, you can either replace the faulty part yourself or call plumber to ask for help.
However, most dishwasher can work without any water pressure at all; they only need to be connected to your faucet and hot water line, which can run even if it’s not much strong.
If you’re having problems with the drainage of water after the cycle has completed, there might actually be too much difference between the “high” and “low” levels of your dishwasher.
So, low water pressure in the whole house is actually a pretty complicated thing. There are three main reasons for this problem, and all of them require different solutions. It’s best to consult a plumber to see what exactly your home needs to solve its flow rate problems.
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