When To Install a Check Valve in Your Pool Plumbing


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This guide discusses the function of a pool check valve and when and where to install it in your pool's circulation system.

Step by Step


Step 1

PURPOSE OF A CHECK VALVE - In general a pool check valve in installed in your circulation system to keep water from flowing backwards in the system when the pump is turned off. Common uses of a check valve are discussed in the following steps.

Step 2

CHLORINATION - Most pools have an automatic chlorination device like a chlorinator or a salt chlorination generator. The concentrated chlorine level that is discharged from these devices should not flow thru your pool equipment and for this reason the device is installed as the last unit before water is returned to the pool. To prevent water from backing up thru the system after the pump is shut off, a check valve must be installed just before the chlorination device - on the side going to your filter of heater.

Step 3

SOLAR HEATING - Most solar panels are installed on a house's roof 8' above the pump. To capture the sun's heat efficiently the piping in the solar panels must be full of water continuously. Without a check valve to stop backward flow, the water in the piping would be suck back down when the pump is shut off. The check valve should be installed in the pipe leading up to the solar panels.

Step 4

SPA - The level water in your spa is often higher than the water level in your pool. When water to the spa is shut off, the spa water level would drain to the level of the pool water. A check valve is installed to maintain the level of the spa water.

Step 5

WATER FEATURES - Many water features have reservoirs. A check valve is installed in the line to the water feature to keep the reservoir from draining when the pump is shut off.


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 Posted: 5/9/2019 

For equipment installed in an elevated placement compared to the pool, check valves should be prior to the pump on the suction side to assist with holding water for priming? Thank you.

InyoPools Product Specialist  Posted: 5/9/2019 

Yes, if the pump is in an elevated position, 2-feet or more above the water surface, a check valve would be a great way to maintain a prime.

 Posted: 10/10/2018 

Hi inyo, Thanks for all the information you've put online, it's great! I've just bought a 3 speed pump that I'm going to install, but my previous pump seems to have air permanently in the lid with no real air bubbles coming back into the pool at the jets. I can't find an air leak. When I manually prime the pump water just flows down the suction side into the pool and leaves air in the top of the pump. Should I be installing a check valve prior to the pump to stop this, or should I be looking even harder for an air leak? Thanks

InyoPools Product Specialist  Posted: 10/10/2018 

Hello Graham - If you are only using the lower speeds on your multispeed pump, the strainer housing may not completely fill with water. Since there are no air bubbles flowing from your jets there does not appear to be an air leak.If you have a cartridge or DE filter you can try the air relief valve to clear out any trapped air. But I wouldn't be too worried until you begin having trouble priming or see bubbles.

 Posted: 9/10/2018 

Hello Rodney - You can install a check valve after a chlorinator but it won't protect your heater or filter. The purpose of the check valve is to prevent highly concentrated chlorine from flowing back to your equipment.

 Posted: 9/10/2018 

Can the check valve be installed after the chlorinator?

 Posted: 12/19/2017 

Dale - Even though the Salt Chlorine Generator is not producing chlorine when the pump is off, there is a concentrated level of chlorine in the water between the SCG and the returns. When the pump is shut off, there is often a reverse flow of water back into the system. This backflow water after the SCG could damage the equipment before the SCG.

 Posted: 12/13/2017 

why is a check valve required for a salt cell generator? when power is off to both the pump and salt cell its no longer generating chlorine. i understand the need for an erosion chlorination device where concentrated chlorine can be produced after the system is powered down, but a salt cell doesn't produce chlorine after the power is off. Please advise why additional pressure drop should be added to the plumbing via a check valve, if it doesn't really add value in a salt cell system.

InyoPools Product Specialist  Posted: 5/15/2017 

Tom murphy - Yes, a check valve can be mounted in any position. They are operated by water pressure against the flapper of spring.

 Posted: 5/13/2017 

Can the check valve be mounted in a hormonal position ?