Usually sitting at the top of your pool filter, the pressure gauge can look very insignificant and unimportant.
But like what the famous quote says: “Don’t judge a book by its cover,” because that insignificant piece of equipment plays a vital role in understanding the condition of your pool filter system.
Understanding this device may seem daunting, but in this comprehensive guide, we will help you understand how a pressure gauge works, its importance, and how to use it for troubleshooting.
What Is A Pool Filter Pressure Gauge?
As the name implies, a pool filter pressure gauge measures the amount of pressure inside the pool filter. Usually, people only know pressure as psi or pounds per square inch, but it’s more than that.
So what is pressure? Technically speaking, pressure is the amount of force applied by a fluid over a surface area. Pressure is only applicable to fluids, such as liquids and gases, because their molecules are free moving. And since we are working with water in a swimming pool, pressure is an important measurement to gauge the filter status.
Pressure gauges are one the most used measuring instruments and have a wide application of uses not only in the swimming pool industry but in the engineering field as well. That is why pressure gauges have a lot of types and have become more and more advanced as technology progresses. 
But since pool filters do not require complex operating reading and pinpoint accuracy, the traditional mechanical pressure gauge is enough for pool maintenance. And although modern pool filters have built-in pressure gauges, some opt to install multiple pressure gauges for cross-checking. We’ll discuss more on this later in the troubleshooting tips.
Why is A Pool Filter Pressure Gauge Important?
As we have briefly mentioned, the readings of a swimming pool filter pressure gauge are important in knowing the current status of the pool filtration system. How? Let’s take a moment first to consider how the pool filtration system works.
A pool filtration system consists of a pool pump, a pool filter, a chlorinator, pipes, valves, and sometimes a heater. Through moving mechanical parts, a pool pump makes water flow from the pool skimmer and pool drain to the filter and back again into the pool.
This normal operating flow creates a baseline pressure reading or what we call normal pressure. On most filtration systems, these normal pressure or baseline pressure readings range from 8 to 10 pounds per square inch (psi).
Now let’s say we turn off the pump. Since there is no pool water flow, we can expect that there will be no pressure reading on the pressure gauge.
Now, what if the filter gets too dirty and gets clogged? Then expect the pressure readings to increase since the pump continues to apply force to the pool water without any release. Don’t worry. It won’t explode because there is always an installed air relief valve in a filter.
How Does A Pool Filter Pressure Gauge Work?
Now that we know what a pool filter is, what it does, and its importance, let’s now take a closer look at how it works. In other words, how it is able to read pool water pressure.
For this discussion, we will only be considering the most basic and most used type of pressure gauge, the mechanical filter pressure gauge.
There are more than four types of measuring elements for pressure. But we will only talk about two, the Bourdon tube type and the diaphragm type, since these are the most commonly installed gauges. Both of these types work using the same principle: elastic deformation due to pressure changes. 
The Bourdon tube pressure gauge uses a circular hollow metallic tube that straightens when the pressure changes. The tip of the tube is attached to a connecting link and pinion gear which moves the needle pointer on the scale.
The diaphragm type uses a circular diaphragm, clamped between two circular flanges, that change shape due to the changes in water pressure. Connecting link and gears are attached to this diaphragm that moves the needle pointer of the pressure gauge.
How To Use A Pool Filter Pressure Gauge?
Now that we have a grasp on the workings of a pressure gauge, it’s now time to learn how to use it. We will talk about this in two sections: operating and troubleshooting.
Operating Using A Pool Filter Pressure Gauge
If “using a pool filter pressure gauge” can be summed up in one word, it would be “monitoring.” Yes, if you want to use a filter pressure gauge properly, then you only need to monitor it.
But first, you’ll need to ensure that it is working properly: no leak, not clogged, and needle pointer is working. If not, then you may need to replace it, which is what we’ll talk about later.
Monitoring the operating pressure requires you to set a baseline pressure for operation. It would be better if you know what this is right after installation. But don’t worry, most built-in pressure gauges on a filter tank have indicators on the gauge on what is the normal range. Or, if there is none, record the pressure reading after cleaning or backwashing the pool filter as your baseline pressure.
Ready a monitoring sheet. You’ll need to record what the gauge read after turning on the pump at the start of operation and before turning off the pump at the end of the day. This way you’ll get the pressure trends of your filtration system and can adjust your cleaning schedule accordingly.
Troubleshooting Using A Pool Filter Pressure Gauge
Significant changes in filter pressure reading indicate that there is a problem with the filters. So you’ll need to troubleshoot it. Below we’ll discuss three possible scenarios that you’ll encounter on a pool filter gauge.
What A Low Filter Pressure Reading Means
If your pool filter gauge gives a lower reading than your baseline pressure, then it means that there is a low flow of water in the system.
So you’ll need to check for excessive leaks, clogs before the filter, or debris build-up in the system. You can check your skimmer basket, pump basket, pool drain, and pipes for blockage.
If there are no clogs present, then there could be problems in your pump, such as a damaged impeller, damage in the motor, or too much water leak. Or, if the pump is above the water level of the swimming pool, you may need to check the priming of the pump.
What A High Filter Pressure Reading Means
The next possible scenario is having a high filter pressure in the system. Usually, this problem means that your pool filter is dirty. For a sand filter and DE filter, you’ll need to backwash it. And for a cartridge filter, you’ll need to manually disassemble and clean it.
Read here how to properly backwash your pool filter to keep it clean and hygienic.
If you have already cleaned or backwashed it, but the filter pressure remains high while running, this means that there are other problems that are causing it.
The first one that can cause it is that your filter media is too old, so you’ll need to replace it. This is to be expected if your filter media have been in operation for too long.
The second one is that there is air inside the system. A good indicator of air inside the system is that parts of the equipment will feel hot due to air being compressed. Don’t worry. Just use the air relief valve to purge the air out of the system.
How To Know If You Need To Replace Pool Filter Gauge
If in case you’ve done all the troubleshooting above, and the pressure reading is still high or low, then the pressure gauge may be the problem. If so, you’ll need to replace the gauge you are using.
One thing you can do to fully check if it’s broken is to test it. A quick test would be turning on and off the pump and then check for movement in the dial indicator. A good pressure gauge will move according to the changes in the flow of water. But if you’ve turned it on and off but the dial indicator gets stuck at some point then you’ll need a replacement for it.
Another test you can do is to buy a new gauge, since it’s not really that expensive, then install it on the filter. It only costs around $10 to $25, depending on the accuracy. Though there are two things that you should check before buying a replacement: working pressure range and size of pipe connection.
In summary, the pressure gauge is an essential part of your filter system. It acts as a monitoring device. It tells you the current running condition of your filter system and if there’s a problem that needs to be addressed.
As its name implies, the pressure gauge works by its moving mechanical parts that measure the force applied by the water pressure. The amount of force or pressure is then reflected on the dial gauge to which it is connected.
If the pressure reading is high or low, it indicates that there are problems inside the system or it could be that the gauge is defective. You’ll need to troubleshoot to know the reason.
Learn why a pool filter is essential and how to choose the right one for your home. Read also our collection of pool-related articles to find interesting reads. I’m sure you’ll discover a lot about Pools.