I'd just like to take a minute to say that thanks too this forum my hottub(and pool) are troublefree!
The pool is sparkly and the hottub is too. It's SOO simple to keep the tub looking great, even having 3-5 teens in it at least twice a week for anywhere from 30 min. to 3 hrs. Had 5 teens in for 3hrs total yesterday actually . I just use the simple OTO test for PH and Cl. I don't even test the PH often. I check chlorine daily when the tub isn't being used.
When we have people over I check the Cl 10-20 min before we get in and usually add 1/8 cup to bring it to 4-5 ppm. Depending on how many people and how long we're in, I'll check the cl. multiple times. If it's low, I'll add another 1/8 cup to bring it back up. I just pour it in the skimmer and don't even bother with making everyone get out.
PH makes its way to 7.8ish and stays there for as long as I keep the water in the tub. I drain into and refill from the pool whenever the water looses its sparkly clarity. I've done this twice so far.
No complaints from any bathers, nobodies gotten sick, nobody comes out itchy. Nobody complains of a strong chlorine smell either, but EVERYBODY enjoys it.
Just like to give a GREAT BIG THANKS to everyone and the Pool Calc. for helping me maintain a trouble free very fun hottub and pool!
P.S. The solar heat works WONDERFULLY! On a sunny day I can go from 90 to 120 in 2-3 hrs.