Most swimming pool owners take for granted the significance of one of the simplest gadgets included in their pool equipment, the pressure gauge on the main pool filter. This one instrument is the equivalent of a thermometer to the human body. When the variance from 98.6 is too large, either high or low, we know our body is sick and needs attention. The same rule applies to the pressure gauge on a main swimming pool filter. Used properly it can be a pool owner's best tool to avoid, diagnose, and solve common pool problems.
The first key to using the pool filter pressure gauge as the tool it is intended to be is to establish and document a "normal operating pressure". This reading should be established immediately after the filter cartridges have been cleaned or when new cartridges are installed. Record this reading, in other words write it down, and store it somewhere that is convenient and easily accessible during your daily or weekly pool maintenance routine.
Then, simply make sure to consult the pressure gauge each and every time you service the pool. Don't be lazy about checking the pressure. It literally only takes a second or two and it could help avoid a hefty pool repair bill and the embarrassment of a green swimming pool. Typically the main filter should be cleaned or backwashed when the pressure rises no more than 10 psi. But as you monitor the pressure gauge, if the pressure seems abnormally high or low, it means the pool needs attention. Of course it is always possible that the gauge itself could be broken, but for this discussion we will assume it is in good working order.
Pressure Abnormally Low - if the pressure gauge is reading lower than expected it could indicate several different problems. Typically it means something is obstructing the water from getting to the filter. Check to make sure there is an adequate water level in the pool. If the water level is good, check all baskets to make sure they are not clogged with debris and blocking the water flow. Also check the skimmer weir door to make sure it is not stuck in the closed position (up). Another common problem is debris getting past the pump basket and clogging up the impeller.
Pressure Abnormally High - if the pressure gauge is reading extremely high, it most likely means the filter media is clogged and needs to be cleaned. Another common reason for a high pressure reading is a valve to one of the return lines has been accidentally moved to the closed position. When this happens the water is obstructed from moving back into the swimming pool, which leads to back pressure to the filter and a abnormally high reading.
Unstable Pressure Readings - if the pressure reading is not stabilizing and constantly moving from low to high and back to low, it usually indicates an insufficient water level in the pool or a skimmer weir that is getting stuck. In either of these cases, there isn't enough water to consistently supply the pump. When there is sufficient water supply the pressure goes up and when the pump starts drawing air the pressure goes down. This is known as "cycling" and should be avoided because it will inevitably lead to damage to the pump motor.
Out of all the tools used to maintain your swimming pool, the main pool filter pressure gauge can be your best friend and save you a lot of time and money in the long run. Monitored properly, the pressure readings will actually tell you a story of the status of the pool in just a few seconds. It is worth the time to document the readings on your main pool filter pressure gauge and start listening to the story it's trying to tell you!
