Duckbill Valve in Chlorine Pump Not Sealing

[DUCK01]

I’ve had a Stenner chlorine pump for 2+ years with no issues. I replaced all of the lines, injectors, and the feed tube this past Spring.

Starting last month, I noticed my FC levels were really low even though everything was running status quo. I’d manually dose to bring up my FC levels and keep the pool balanced.

My 15 gallon tank was almost empty on Thursday, so I picked up 15 more gallons from Pinch A Penny on Friday. When I opened the tank to fill it, it was almost full. Pool water had backflowed into tank, meaning the duckbill valve had failed. I got the tank emptied and refilled with chlorine and replaced the duckbill. I’ve been monitoring since then and am still getting pool water back flowing past the duckbill valve.



If I stop the pump, pull out the duckbill valve and rinse it off, it seals and the water no longer backflows. I’ve tried three different valves and they all perform the same.

I found an injection port that uses a spring loaded check valve instead of a duckbill, but don’t know if that’ll help, considering duckbills have worked fine for 2 years. Is there something else I should check? I think I’ll replace the feed tube to ensure it’s tight and sealing well. After that, I’m at a loss.

 

[PoolStored]

Have you ever cleaned the tank and replaced the lines? Salts can form anywhere and migrate to the duck bill and get lodged leaving it open.

 

[DUCK01]

I cleaned the tank really well when I drained it on Friday. All of the components are salt free (I replaced the injection valve yesterday) and removed quite a bit of salt from the inside of the cap and tee where the injection valve resides. Based on what came out, you’re likely right about that being the cause of the 10 gallons of backflow on Thursday/Friday. All of the tubing is only a few months old and I ran chlorine into a cup for a while last week to measure output and to make sure there wasn’t any salt in the line that was preventing a normal flow of chlorine. It was clean when I was troubleshooting to figure out while my chlorine levels were so low last month. Knowing what I know now, that’s because I was pumping super diluted chlorine into my pool due to the backflow issue I’m currently chasing.

I just replaced the white feed tube based on info I found on an old thread from 2015. Aftee running the Stenner pump on manual for a few minutes to prime everything, there’s still a little bit of water back flowing through the duckbill valve in the injection port. I can’t say that that’s abnormal, so I hooked the tubing back up to the injection port and unhooked the line that runs from the tank to the feed tube on the Stenner pump. I have a cup under the inlet side of the feed tube and will see if there’s any backflow. I’m betting that there’s always been some small level of backflow through the injection port, but the tension of the feed tube is enough to block it from going back into the tank.

I’ll update after an hour or two and see if replacing the white feed tube was the fix.

 

[DUCK01]

Just to wrap this up, replacing the white feed tube seems to have done the trick. After an hour, there’s no water getting through to the inlet side of the feed tube.

The duckbill by itself isn’t enough to prevent water from migrating back into the holding tank when the pool pump is running, but the pressure is so low that any pool water won’t make it through a good pliable feed tube. The rollers must hold enough pressure to block off any low flow of pool water back flowing through the system.

 

[Lake Placid]

For about $16 on Amazon, you can install a Stenner AK600 or AK700 flow indicator after the pump which will allow you to visually see if you’re feeding correctly and also act as a check valve behind the duckbill valve. You could also move to a Stenner ball check valve instead of the duckbill valve.