You need something to test the water - some use test strips others use liquid drop kits. The best kit IMO is the Taylor K-2005, it tests for everything and it has a great water balancing and troubleshooting guide. Always test your water with lower chlorine in the water, anything over say 5 PPM will make the readings wrong.
First you need to have your fill water tested to see where that is. Once you know that ...
PH - 7.2 - 7.6 range
Calcium - 150 - 400 PPM
Alkalinity - 80 - 120 PPM
You can add PH down to adjust alk and PH down, baking soda to adjust those up. If Alkalinity is OK and you need to adjust PH up - add soda ash.
Calcium if it's too high may be a problem, maybe someone can address that - I don't have that problem. If you need to add calcium, then get some calcium increaser. You can buy larger lots at a pool store (same as with PH down)
Now for chlorine (dichlor) you want to add enough to get a 2 to 3 PPM reading 20 minutes after you add it. If you go to
http://www.rhtubs.com/bbs/FAQ.htm and 1/2 way down is Northman's and Vermonter's guides. Most of us follow these for our tubs.
Adding chlorine may be as simple as adding 1 teaspoon per person depending on the gallons ... the smaller the tub the less you need to add to get to that desired level.
I have a 400 gallon tub and typically use 1 teaspoon per person (1.5 PPM). You also may need to add chlorine when you don't use the tub ... hot water can go bad (cloudy from bacteria) in a day. Continual adding of chlorine (I add every other day) will keep the bacteria in check and the tub safe.
Every so often you need to shock either with dichlor or something called MPS (a long sceintific compound name).
Reading it may seem dificult but it really is EASY!
