Spa has brown ring at the waterline?

[CalMan]

700 gal spa overflows into the 15,000 gal pool and I run in overflow for 4 hours each morning with the chlorine generator (pool pilot) at 100%. At the end of the 4 hours the chlorine is at 2 PPM. By the next morning, the chlorine is down to about 1ppm. pH is between 7.5 and 7.8.

With no one using the spa, each day there is a brown ring in the spa at the water line. It washes off easily, but I'm concerned that something is wrong. Can anyone tell me what's going on?

Thanks,

al

[waterbear]

Post a full set of test results including FC, TC, pH, ALKm CH, CYA, and Salt and also the finish of the spa and pool (plaster, fiberglass, vinyl) so the good folks on the forum can get an idea of what is going on in your pool. Also, what type of filter are you using and is the pool new construction or an established pool. It would also be helpful to note any other chemicals or additives you might be using (enzymes, clarifiers, metal treaments, algawcides, etc.) The airation from the spa jets sometimes can cause some products to create more of a scum line in the spa than in the pool.