What is a Pressure Gauge and How Does It Work?

We asked our certified Master Water Specialist, John Woodard, to give us some insight on pressure gauges. In this video, he'll help you understand exactly what a pressure gauge is and how it can improve your water treatment system. Here's John's expert knowledge on what to expect when using a pressure gauge.

What is a pressure gauge? 

A pressure gauge is a device that helps monitor performance parameters. Our water systems and tanks function because the water or air that runs through them is pressurized. A pressure gauge measures the force of the pressure in the water or air so that you can determine whether you have any errors in your tanks or systems.  

What is a pressure gauge's purpose? 

Pressure gauges are used for a variety of things. We can use them to gauge household pressure if we want to see if the pressure regulator on the house is still working. We use them on a storage tank for a well system to make sure the pump is turning on and off properly. And, we use them on water treatment equipment or things like reverse osmosis where pressure is a key component to the operation of that system. Sometimes, even a simple tire gauge enables us to test pressures on a storage tank. 

There are two main types of pressure gauges 

Pressure gauges come in a lot of different forms, but the two most common types of pressure gauges used in the water treatment industry are the manometer (U-tube) and the bourdon tube gauges. 

Manometer (U-tube) 

Manometer-style pressure gauges contain a little U-shaped tube with liquid in it. When pressure is applied to either side of the gauge, the water in the tube rises one way or the other, and you can determine how pressurized your system is by reading the markings indicated by this tube.

Bourdon tube 

The bourdon-type pressure gauge is most commonly used in the water industry because it is very easy to use. It has a readable dial with a needle that points right to the operating pressure. They can be used on storage tanks for well systems to let you know if your pump is working properly. They can also be used on a filter setup to gauge how much pressure is entering the filter and how much pressure is leaving it. 

The bourdon tube type of gauge contains a little, sealed tube on the inside. When pressurized liquid or air enters the gauge, that little curved tube will begin to straighten out, just like a balloon does when you start putting air into it. As the tube straightens, it interacts with the gears on the inside to move the needle. These gauges are preset to measure a certain range of pressures, so there is no need to try and calibrate them yourself. 

What is the pressure differential? 

Pressure differential is the variance, or the delta, between two pressures. In any given filter application, we have a certain pressure coming in, and a certain pressure going out. The difference between those two pressures is the differential. So, the higher the variance, the more pressure drop you will experience across that filter. 

How do you know if pressure is too high or too low? 

Pressure gauges come in a variety of calibrations. They can range 0 to 15 pounds per square inch (PSI), all the way up to a range of 0 to 1,000 PSI. So, the trick with a pressure gauge is to make sure the gauge that you are using is compatible with the scale of the application you are using it in. You can determine whether the pressure is too high or too low based on what parameters you are looking to operate under. 

What does it mean if our pressure is too low?

Pressure gauges provide information that allows us to monitor equipment. If we see pressure going too high or low, it could be an indication that we need to fix something in our tank or filter system. For example, if we are monitoring pressure differential across the inside of a filter and the outside, or the effluent side, of that filter, and the pressure is dropping way low, it may mean that the filter is clogged up and needs to be changed. If you do not take action, it could stop water from flowing into your house or through your equipment.  

What does it mean if our pressure is too high?

If the pressure on your gauge reads too high, you may also have to take action. Extra-high pressure could result in a catastrophic failure. Fittings or tubing could burst, or housings could come apart. If this happens, you will begin to experience leaks that could result in flooding and be potentially dangerous for your home or office. 

How do you install a pressure gauge? 

Pressure gauges typically come with a threaded mount that you either put into a pipe fitting or into a manifold. The location of those threads on the gauge determine where and how you install your pressure gauge. Some of the gauges come with threads on the very bottom. The gauge is typically mounted to the top of a filter housing or some type of plumbing configuration. Other gauges that come with the threads on the very back would need to be mounted on a panel or system that is configured to face you. 

How do you calibrate a pressure gauge? 

Calibrating a pressure gauge is fairly complex, depending upon the style of gauge or the accuracy that you are looking for. Sometimes, calibration on a periodic basis is necessary. For example, if you are treating water in an application where a very specific pressure has to be met, it is very important that your meter, or gauge, is calibrated correctly. These gauges come in different accuracy classifications. In the water treatment industry, typically for residential or light commercial use, calibration is not quite as necessary, or as frequently needed, as something that requires ultimate accuracy. 

How do you read a pressure gauge? 

You can read a pressure gauge by simply matching the needle to the number on the dial. Digital pressure gauges will read the exact PSI, and an air pressure gauge, like a tire gauge, will shoot out a little stick marked with measurements of PSI. The stick will line up with the end of the gauge so you can read the pressure. 

What does it mean if the pressure gauge reads negative?

It is pretty obvious that a pressure gauge reading a negative number has a problem. Typically, pressure gauges range from zero up to any positive number. So, if your gauge is showing a negative number, either the gauge is malfunctioning, or it’s working on a vacuum that is pulling the bourdon tube into a further curve, which would make the needle go down. It could be that the meter is calibrated poorly or needs calibration. 

Pressure gauges are great tools for measuring the pressure of your water treatment systems. They enable us to really look at how our equipment is operating, and how our filters are performing. They are, very specifically, monitoring devices. A pressure gauge is not going to create a problem, but it will certainly tell you if you have a problem with any of your water filtration equipment or systems.