Infinity Edge Pool possible problem

[Losmond]

We have an infinity edge pool and today we installed a timer on the pump so it wouldn't run 24 hours a day. After a couple of hours the pool water lever was down 3" below the edge and the catch tank which the water level is usually 12" below the top was overflowing. Im guessing this is a symptom of gravity but does this mean my pump needs to run 24 hours a day?

[Denniswiseman]

I would suspect that the catch tank is piped into the pool which will try to equalise levels
I would assume that it should only pull from the catch tank and then pump over into the pool
A check valve (non return) on the suction line from the catch tank should stop the pool water flowing back into the catch tank and overflowing

[Teapot]

Spot on