When air pockets form in your swimming pool filtration system the pump has to work harder to circulate water through the filter and into the pool. The system loses efficiency and operates with reduced performance resulting in less than clean pool water.
Learn how to bleed air from your pool filter by running the pump and opening the pressure relief valve located at the top of the tank. When air is trapped in the filter it becomes compressed at the top of the filter tank. Check the reading on the filter pressure gauge. When the reading is high it indicates there is air trapped in the system. Open the air pressure relief valve to clear the build-up of air pressure in the filter. Close the relief valve when water shoots out of the valve indicating all the air has been released. Now the reading on the filter pressure gauge should be back in the normal operating range.
Table of Contents
How is Air Trapped in the Pool Filter
The pool filtration system is an air tight (and water tight) system. If there are any leaks in the system it will cause problems leading to reduced filtration and unclean pool water.
Here are the most common reasons for air becoming trapped in the pool filter.
Skimmer Flap Stuck
A pool skimmer is a plastic box fitting with a rectangular opening built into the side wall of the pool. The skimmer box has a weir flap that floats open and closed with the water level and pump suction. When the pump is off the weir flap floats to the closed position preventing trapped debris drifting back into the pool. When the pump is operating the weir flap is drawn open and pool water flows into the skimmer box.
Sometimes the skimmer weir flap becomes partially stuck due to debris causing the skimmer box to quickly empty of water when the pump is running. The pump draws air into the plumbing which ends up in the filter tank.
Ensure the skimmer flap is clean and free of debris to operate correctly.
Low Pool Water Level
The pool water level determines how effectively the skimmer box cleans the surface of the pool. The pool water level only has to be slightly lower than normal for the skimmer flap to not open fully when the pump is running. Surface debris will not be drawn into the skimmer box.
If the water level is too low the skimmer box will partially empty of water when the pump is running. This will cause air to be drawn into the plumbing which is eventually trapped in the filter tank. Ensure the pool water level is at least midway up the skimmer flap.
Note: Never let the skimmer box run dry as this will damage your pump motor. Pool pumps must have water flowing through them to operate properly. Without water the pump will over-heat and burn out.
Plumbing Leak
There may be a tiny leak in the plumbing pipes where outside air is being drawn into the pipes where it makes its way to the filter. Theses leaks most often occur in the pipe joiners where the pipe fits into a bend connector or three-way connector. There is a tiny leak in the join and the pump pressure sucks in air through the leaking joiner. Usually it’s caused by pipe joining glue failure or not enough glue was used when first installed.
These leaks are difficult to detect as air is sucked inwards rather than pushed outwards. If there is water dripping from a join then that indicates there is a leak. If water can leak out then air can be sucked inwards as well. Spray soapy water over the suspected leak when the pump is running to check if soap suds are drawn into the valve.
When you find the leak the joiner has to be replaced with a new joiner and plenty of pipe joiner glue.
Pump Basket Lid Leak
The pump basket lid is a clear plastic screw on lid that allows easy access to the pump basket. Sometimes the pump basket lid is not screwed up tight and air can be drawn through the screw mounting. Always ensure the lid is screwed on properly and is air tight.
Check the lid rubber gasket for wear and tear. There may be a tiny split or tear in the gasket which would need to be replaced.
Filter Tank Leak
A filter tank leak will not cause air to trap in the filter but water will leak from the filter tank.
Cartridge filter tanks have a screw on lid that allows easy access to the filter cartridge for removal and cleaning. A leak may be caused if the lid is not screwed up tight or the lid seal gasket is worn.
Sand filters can leak water when the seal gasket is worn or split.
Vacuuming the Pool
When vacuuming the pool you may have inadvertently introduced an air pocket when connecting the vacuum hose to the skimmer box plate or pipe. Before connecting up the vacuum hose hold it over an outlet jet with the pump running to expel air from the hose.
The vacuum hose may have a split or leak at the end where it is exposed to the air and is drawing air into the pump. If the hose has a leak it’s time to replace it.
Trapped Air after Cleaning the Filter
After opening the filter tank and cleaning the filter air will be trapped in the filter tank. Once the pump is switched on the trapped air will be compressed at the top of the tank. The trapped air should be bleed from the system. The filter will still work but not as efficiently as when there is no air in the system.
Air Pockets after Refilling the Pool
When a pool is emptied the water also drains from the plumbing pipes and filtration system. When the pool is refilled with water it created air pockets in the filtration system and plumbing. Most of the air is pushed through to the pump and filter.
The Pool was Prepared for the Winter
When a swimming pool is prepared for the winter the water is flushed out of the plumbing lines to prevent ice forming and damaging the pipes. When you are opening the pool for the summer season you need to remove air in the system to prime the pump.
Please read our article on How to Prepare Your Pool for Winter
Pump Valve in Wrong Position
An incorrectly positioned pump valve or multiport valve may allow air to be drawn into the plumbing from the drain. The valve may not be fully clicked into the position and the inside of the valve is leaking to another port. Always ensure your valve handle is correctly locked into position.
Multiport Valve Gasket Leak
A pump valve or multiport valve with a worn gasket seal may allow air into the system.
Spray soapy water over the valve when the pump is running to check if soap suds are drawn into the valve. If there is a leak replace the gasket seal.
How to Bleed Air from a Pool Filter
All filter tanks (cartridge and sand) have a pressure relief valve located at the top of the tank. When air is in the filtration system it becomes trapped and compressed at the top of the filter tank.
Opening the air pressure relief valve clears the build-up of air pressure.
- Run the pump motor with the multiport valve in the default “filter” position.
- Check the pressure gauge. If the reading is above 10psi there may be air in the system.
- Slowly open the pressure relief valve. Be ready for a hiss of compressed air. Release all the trapped air.
- When water shoots out of the valve all the air has been forced out. You can close the valve now.
- Check the pressure gauge again. Has the reading reduced?
- The gauge reading should be back in the normal pressure range for your type of filter.
- If the pressure is still high, repeat the process until all air has been expelled from the tank.
Always perform this procedure to bleed air from your pool filter after cleaning your filter as there will be an air pocket in the tank.
Conclusion
How to bleed air from your pool filter tank is a simple operation and should be part of your normal pool servicing routine. Bleed the air every time the filter tank is opened or backwashed. Also bleed the air after the pump basket has been cleaned.
If you have any questions or would like to know more information, please leave a comment below and we will get back to you as soon as possible.
