Quote Originally Posted by waterbear View Post
If your water level drops when running the spa jets then start looking for a leak or possibly a back check valve in the spa return line.
Adding dry acid "a little at a time" is not going to do the job. You need to drop the pH to 7.0, test TA, then aerate to bring it above 7.4 and repeat this until the TA is on target. You do not need to aerate but it will take longer for the carbon dioxide to gas off. There are other ways to aerate besides using your spa jets BUT if your water level drops when running the spa jets then start looking for a leak or possibly a back check valve in the spa return line.
Oh, no, my water level isn't dropping while the system is on. It's just that once the filter pump shuts off, water stops pumping into the spa (which is what creates the waterfall), and then the water in the spa "seeks its own level" with the pool. I was told by the pool company that this is normal. Is that wrong?

BTW, you're probably right about not having a big chlorine demand right now. I'm on Long Island, NY, and the weather is turning cool as well as having some cloudy, rainy days. We keep our pool open into October because we use the spa at night in cool weather, but we'll be closing it fairly soon. We did have warm weather the past two weekends, heated the pool, and did swim all day, though. Our pool temp had been up to about 90 last weekend; now it's down to about 65. Cooler water and less sun means less chlorine demand, right?