The pool filter pressure gauge indicates the water pressure within the filtration system. It’s the only item of instrumentation that tells you about the condition of your pool filter. High pressure indicates the skimmer basket and filter media requires cleaning. Low pressure indicates there is a hole in the filter media and water is bypassing the filter.
Table of Contents
What is a Pool Filter Pressure Gauge
A pool filter pressure gauge indicates the water pressure within the filter tank usually in units of pounds per square inch (psi) or kilo Pascals (kPa).
A standard pool filter pressure gauge reads from 0 to 60 psi.
Pool filters work by passing dirty pool water under pressure through a filter media to clean the water. A pool filter works at optimal efficiency when the water pressure is within a normal operating range.
Check the pool filter pressure gauge every week as part of your pool maintenance routine. When the pressure is high clean the filter to ensure the pool is kept clean and clear.
What Should the Pool Filter Pressure Gauge Read?
The reading on a pool filter pressure gauge varies between models and types of filter. Most filters have a normal operating range of 5 to 20 psi (30kPa to 130kPa).
The reading depends on a few factors:
- The type of filter – cartridge, sand or DE filter
- The type of filter media in the filter tank
- The age of the filter media
- The power of the pump motor
- The diameter of the plumbing pipes
- Distance between the pump and pool
- Additional equipment – chlorinator, water heater
Please read the manufacturer’s operating instructions to find out what is the normal pressure operating range for your filtration system.
Otherwise, follow this procedure to find out the low end of the pressure operating range. Clean the skimmer and pump baskets and install a new cartridge element or sand in the filter tank. Run the pump and note the reading on the filter pressure gauge. This reading is your lowest pressure reading.
Clean the filter cartridge element once the pressure gauge has reached 50kPa (7 or 8psi) above the normal operating pressure. For example, a filter that normally operates at 50kPa (8psi) needs to be cleaned at 100kPa (15psi).
Pool Filter Pressure Gauge is Low
If the water pressure in the filter is too low the filter will not clean the pool water effectively. This usually indicates a blockage restricting water flow to the pump.
Common causes are:
- Dirty skimmer basket
- Blocked pump basket
- Main valve set in an incorrect position
- Multiport valve is not set correctly
- Blockage in the plumbing before the pump
- Undissolved salt in the plumbing system. Remove the filter cartridge and run the pump to clear it.
Low pressure can also occur when there is a hole in the filter cartridge and water is bypassing the filter element.
Pool Filter Pressure Gauge is High
If the water pressure in the filter is too high the water flow is too weak and the filter will not turn over enough water to clean the pool. This usually indicates a blockage restricting water flow after the pump to the filter or after the filter back to the pool.
Usually, the water pressure gradually increases as the filter fills up with dirt and debris. Cleaning the filter reduces the water pressure back down to the normal operating pressure.
Common causes are:
- Pool filter is dirty
- Pool filter element is old and needs replacement
- Filter media (sand) needs replacement
- Multiport valve is not set correctly
- The water heater has a blockage
- The saltwater chlorinator has a blockage
- Return jets are blocked or too small
- Undissolved salt in the plumbing system. Remove the filter cartridge and run the pump to clear it.
- Calcium scale build-up in the plumbing pipes
The high pressure may cause damage to the filter cartridge or other equipment. The pump motor will run hot while straining to move the water through the filter.
How to Reduce High Pressure in a Pool Filter System
When your pool filter pressure gauge is reading more than 10psi the system starts to become less operationally efficient. Operating the filter at over 20 psi is too high and puts a strain on your pump. The water flow is reduced and the filter cannot clean the pool effectively.
1. Clean the Pool Skimmer Basket
When leaves, insects, or any other larger pieces of debris enter the pool they float on the surface for a while before sinking to the bottom. The skimmer box is a suction device powered by the pool pump. Its purpose is to remove all floating debris from the surface of the pool and trap it in the basket.
When the skimmer basket is dirty it restricts the water flow to the filter. This puts a strain on the pump motor which must work harder to move the water through the filtration system.
Clean the skimmer basket to allow correct water flow in your pool filter system.
2. Clean the Pool Filter
Cartridge Filter
Clean the filter cartridge element with a hose and install back into the filter tank.
If cleaning the element does not reduce the pressure back to the filter’s normal operating pressure the cartridge must be replaced.
When you are cleaning your filter cartridge and you notice it has become more difficult to clean, has any damage to the pleats or won’t clean easily it’s time for a new cartridge.
Please read our article on How to Clean a Pool Cartridge Filter
The cartridge filter element becomes embedded with fine particles of debris that cannot be removed with simple hosing. Hosing only cleans the outside of the cartridge element while the inside becomes more clogged with fine particles.
There are filter cleaning products available that claim to dissolve the embedded fine particles within the element. However, once a cartridge filter has become clogged I recommend to replace the cartridge rather than spend money on additional products.
Pool filter cartridges can last from 2 to 4 years depending on how you clean your pool and filter. I recommend replacing the filter cartridge every 3 years.
We recommend having two filter cartridges. When the filter needs cleaning swap out the filter cartridge element with the clean one so your filtration system can operate immediately. Clean the dirty cartridge, dry and store.
Sand Filter
When the pressure increases above a threshold (usually indicated on the gauge) the filter has become dirty and needs backwashing.
When backwashing doesn’t reduce the pressure back to the filter’s normal operating pressure the sand must be replaced.
Please read our article on How to Clean a Pool Sand Filter
3. Suction Air Leak
Air is being sucked into the filter tank through a leakage in a plumbing joiner. The air becomes trapped at the top of the filter tank and is compressed causing high pressure in the tank. The water flow through the filter element is reduced leaving your pool unclean.
4. Over-sized Pump Motor
This is a common problem when an existing pump motor is replaced with a new and more powerful motor. The new motor has an increased capacity and produces higher water pressure through the filtration system. It’s important to always match the power output of the new motor to the power of the old motor.
5. Replace the Return Jets
The return jet covers in the pool may be too small with a narrow opening which will cause higher pressure in the system. You can lower the overall system pressure by replacing the return jet covers with larger opening covers that allow increased water flow thus reducing the overall water pressure.
Pool Filter Pressure Gauge is Not Working
The filter pressure gauge is not working when:
- The needle is stuck on zero.
- The reading on the pressure gauge changes very little.
- The reading does not go to zero when the pump is off.
If your pressure gauge is not working switch off the pump and remove the gauge. See below on how to replace a pool filter pressure gauge.
Try cleaning inside the screw assembly of the pressure gauge. Sometimes the gauge is clogged with fine particles of dirt or pollen.
If you find rust inside the gauge screw assembly you will need to replace the filter gauge. These gauges are inexpensive at around $30.
How to Replace a Pool Filter Pressure Gauge
The pressure gauge on your pool filter may have become old, inaccurate, damaged or unreadable. It’s time to replace the gauge. Gauges are inexpensive (around $30) when you order them online.
1. Order a New Pressure Gauge
Purchase a new pool filter pressure gauge online for the best price.
2. Switch off the Pump Power
Always turn off the power supply to the pump at the wall before doing any work on your filtration system. This will prevent the system from automatically activating causing damage to the system (and spraying water everywhere).
3. Open Filter Relief Valve
Open the relief valve on top of the filter to relieve the pressure from the tank.
4. Remove the Pressure Gauge
Unscrew the pressure gauge in a counter clockwise direction.
If the gauge doesn’t turn easily spray the base of the gauge with a lubricant spray and wait 5 minutes for it to loosen the gauge. Try again to unscrew the gauge.
If the gauge still doesn’t turn easily use small spanner on the nut at the base of the gauge. Try not to apply to much force or you may damage the thread.
5. Apply Teflon Tape
Apply plumbers’ Teflon tape to the thread of the new pressure gauge. Wrap the tape in a clockwise direction so it stays on the thread when screwing on the gauge. Use two or three layers of tape to get the best seal.
6. Screw on the Pressure Gauge
Screw the gauge into the pressure relief valve in a clockwise direction ensuring the tape stays on the thread. Use a small spanner on the nut at the base of the gauge to tighten the final quarter turn. Do not over tighten the gauge. You may want to be able to remove it again in the future.
7. Switch on the Pump Power
Turn on the pump so that you can test the water flow through the filter.
8. Close the Pressure Relief Valve
Close the pressure relief valve when water is escaping from the tank and all air has been forced out of the tank. There must be no air in the system for the filter to function effectively. Also the pump must have water and be completely free of air to function correctly.
Conclusion
The swimming pool filter pressure gauge is a simple device that operates for years without problem. Like measuring the blood pressure in the human body, it displays the water pressure inside the filter which indicates the condition of the filter. When the pressure is too low or high there is a problem. Usually, the water pressure gradually increases as the filter fills up with dirt and debris. Cleaning the filter reduces the water pressure back down to the normal operating pressure. After cleaning, if the pressure is too high or low there is some other issue such as a blockage in the filtration system.
