So I put an inline chlorinator into my system last year-above ground 21 foot round pool. At the end of the season last year after only a few months, I found that my check valve had failed and it was letting the chlorine go back into the filter. I went back to the pool store and they replaced it for free. This year, I again put the check valve in (between the filter and chlorinator) horizontally (and facing the right way and all that) and tested it first by taking the plumbing and putting a garden hose into the end that would be the return end. I turned the water on and it worked perfectly, didn't let water exit on the other side (filter side), only backed up the water toward the return side. 7 days later, I had a suspicion it had failed again and took the plumbing system out and did the garden hose test again. this time, it let the water through the other side (check valve flap not engaging).
I am using trichlor pucks if that matters. Also, the chlorinator is mounted on the ground below the level of the filter and the return on the pool (via 90 degree elbows to get it down there). The brand is FLO and it is a flapper type check valve.
Is this the wrong kind? What am I doing wrong here? The pool store said they will give me another kind-the type that is always closed and needs front pressure to open rather than the flap that is always open and requires back pressure to close. But I am afraid this kind that needs front pressure to open will restrict the flow into the return because of the valve mechanism in the center of the valve (the flapper kind which is very open allows maximum flow)
Please help me, this is VERY frusterating!