Pool Filter Pressure Gauge - How It Works

Pool Filter Pressure Gauge

Pressure gauge on a pool filter system with well-adjusted pressure for optimal filtration of the pool water

Figure 1: Pressure gauge on a pool filter system with well-adjusted pressure for optimal filtration of the pool water

A pool filter pressure gauge measures the pressure inside the pool's filtration system and helps determine when it's time to clean or replace the filter or even replace other plumbing components. They are essential for maintaining a swimming pool's cleanliness and health. By understanding how to interpret the pressure gauge on a pool filter, one can gain insight into the overall functioning of the pool system. This article discusses the critical role of a pool filter pressure gauge in maintaining the proper functioning of a swimming pool and explains how to interpret its readings to assess the overall condition of the pool's filtration system. Read our article on pressure gauges for more information on the working and various types of pressure gauges.

Table of contents

Pressure gauge for pool filter

When water flows through a pool filter as intended, the pressure within the filter remains steady. A pressure gauge, typically attached to the top of the filter, can help monitor pressure levels and fluctuations. Any fluctuations indicated by the pressure gauge may indicate water is not flowing through the filter as it should. Read our article on water pressure gauges for more details on the working and selection criteria of pressure gauges used for water.

What should the pool filter pressure gauge read?

Most pool filter pressure gauges have a bourdon tube element. The normal pressure reading on the gauge depends on several factors, such as:

  • pool and filter size
  • how clean the filter is at the moment
  • the condition of the pool water
  • plumbing on the pool
  • the pool system setup

After installing a new filter, turn on all equipment and record an initial measurement. This initial measurement, known as a baseline reading, should be taken each time the filter is replaced. The baseline reading serves as a reference point for determining the ideal pressure level for your pool. A pressure gauge reading of approximately 10 Psi (0.7 bar) is considered normal.

As part of the regular pool maintenance schedule:

  • Check the pressure gauge on the pool filter at least once a week. If the gauge readings are moving too far in either direction, address it immediately.
  • Note the gauge readings so it can easily be seen if and when the pressure starts to drop or rise. This helps determine if something is wrong for system troubleshooting.

How does a pool filter gauge work

Dirt, oil, and other impurities accumulate on the filter over time. As a result, the water flow gets restricted through the filter. The pool filter gauge is measuring this flow pressure, and according to industry standards, when the pressure gauge indicates a reading of 10 PSI (0.7 bar) above the typical baseline, it indicates that the filter needs to be cleaned to restore an adequate flow rate. The baseline (normal) reading is the pressure gauge reading when the pool filter is installed and everything is running as it should. The user can also refer to the manufacturer’s manual to determine the value.

Pool filter gauge issues

Increase in pool filter pressure

High pressure on a pool filter gauge usually indicates a dirty pool filter. If ignored, increasing pressure in the filter tank can lead to the tank rupturing. If the pressure increases steeply, shut off the pump and check for the following issues:

  • Broken internal filter parts
  • Dirty pool filter
  • Closed or partially closed return side pool valves
  • Lime deposits inside the gas heater heat exchanger

Decrease in filter pressure

A decrease in pressure indicated by the pool filter pressure gauge generally suggests an issue with the water flow before it reaches the filter. Likely there is an obstruction in the skimmer basket, pump basket, pump, or main drain. Other causes of low pressure can be a low water level, an undersized pump, or a leak somewhere in the system.

Pool filter pressure gauge is not working

  • If the gauge appears inactive, try tapping it gently. If this does not work, turn off the pump. The gauge should then read zero. If the gauge remains at zero even when the pump is turned on, the air bleeder assembly under the gauge may be clogged. To fix this, remove the gauge and assembly and clean the air relief valve.
  • The dial may be bent if the pressure gauge needle remains in the same position even when the pump is turned off. This can happen with metal gauges due to rust on the pin that holds the needle or with plastic gauges due to warping from exposure to sunlight. In this case, replace the gauge.

Air relief valve for pool filter

Actions such as cleaning the pump basket or backwashing the filter can trap air in the system. Accumulation of trapped air can lead to an increase in overall pressure within the filter. It is recommended to regularly release this trapped air using an air relief valve, particularly when a slight increase in pressure is observed. The pressure gauge in a pool filter operates with the air relief valve, which releases any air trapped within the filter system.

Filter pressure gauge on the pool is leaking water

At times, it can seem like a pool pressure gauge is leaking water, but it is typically the air relief assembly that leaks rather than the gauge itself. Try the following remedies if the air relief valve leaks:

  • Repair the air relief valve with a Teflon tape
  • Replace the o-ring on the valve knob
  • Install a new air relief valve

Broken pool filter gauge

If the filter pressure remains unchanged for several weeks, it's possible that the gauge is not functioning correctly. Pressure gauges can malfunction for several reasons. An obstructed air bleeder assembly, typically situated beneath the gauge, can cause the pressure gauge to malfunction. To fix this issue, remove the gauge and clean it thoroughly. If the gauge still does not move, replace it with a new one. If the gauge doesn't return to zero when the pump is turned off, it may be a sign that the gauge is faulty and needs to be replaced.

Read our article on troubleshooting pressure gauges for more details on maintenance and troubleshooting pressure gauge issues. For other pressure gauges, see our bellows pressure gauge or diaphragm pressure gauge articles.


How high should the air pressure be on a pool filter?

Clean the filter when the pressure reading exceeds 0.7 bar (10 psi) above the base measurement. Take base measurements after cleaning and backwashing the filter to ensure proper pool operation.

How will I know if my pool pressure gauge is defective?

A broken gauge may read zero or be warped when the pump is on, indicating distortion or deformation due to exposure to high pressures that cause inaccuracies in gauge readings.

What is a pool sand filter pressure gauge?

A sand filter is a filter type that removes suspended, floating, and sinkable particles. A pressure gauge for a pool sand filter helps determine when it's time to clean or replace the filter.

What should the pressure gauge for pool pump read?

A pool pump pressure gauge should normally read between 0.7-1.4 bar (10-20 PSI).