Dichlor/bleach EasyPeasy!

[waterbear]

Get a GOOD test kit. My recommendation is the Taylor K-2006 which uses the FAS-DPD test for FC and CC and is superior to DPD testing. The LaMotte ColorQ is my second choice but it is much more expensive than the Taylor Technologies K-2006 Don't try to balance your water with strips, even with a strip reader. They don't have the required precision.

Balance water in this order:

If CH is less than 150 raise it to 150 to 200 ppm. If it's above 400 ppm add a calcium sequestrant (metal sequestrant) every 1 to 2 weeks and make sure your pH does not go above 8.0 to help prevent scale deposits.

If you know your fill water had metals (iron or copper) treat accordingly with a metal sequestrant.

adjust TA (50 to 70 ppm)

IF needed adjust pH once TA is in range. Maintain pH NO LOWER than 7.6 and NO HIGHER than 8.0

OPTIONAL BUT RECOMMENDED:  Add 50 ppm borate if desired, using boric acid, borax (sodium tetraborate decahydrate), sodium tetraborate pentahydrate, or a commercial borate product for pools and spas.This will help with pH stability and help keep it around 7.8 for a longer time than without. Borax and sodium tetraborate pentahydrate will need the addition of acid to maintain pH since they are alkaline. Boric acid will drop pH slightly but it will rise on it's own once the tub is running The aeration created by the jets will cause the pH in your tub to rise because of the out gassing of CO2 from the water. Most commercial products are a mixture of boric acid and sodium tetraborate pentahydrate so they are pH neutral. Some of the older products on the market are just sodium tetraborate pentahydrate and must be used with the addition of acid. Follow manufacturers directions for commercial products.

Use Dichlor for chlorination until CYA is 30 ppm or slightly higher then switch to bleach. 

Monitor the total amount of FC added, For every 10 ppm FC you are adding 9 ppm CYA with dichlor.

9 parts CYA/10 parts FC = 30 ppm CYA/X ppm FC (solve for X by cross multiplying)

9X=300

X=300/9=33.333 PPM FC added in total (round to 33 and you are close enough, certainly closer than testing CYA because of the inherent error in the CYA test. The FC is more precise.

Now that you know that you have to add 33 ppm FC in total just track how much you have added. So if you fill and shock to 10 ppm, FC dops to 4 ppm and you add enough dichlor to raise it to back to 10 (which means you have added another 6 ppm FC)  you have added 10 + 6 ppm FC at this point.

FC drops to 3 ppm and you bring it up to 8 ppm so you have added another 5 ppm FC for a total of 16 +5=21 ppm.

FC drops to 4 ppm and you bring it up to 7 ppm (adding 3 ppm FC) so you are now at  21 + 3 ppm or 24 ppm.

FC drops to 3 ppm and you shock to 12 ppm  (adding 9 ppm FC) and you are at your target of 33 ppm FC (24 + 9 = 33). At this point stop the bleach and switch to dichlor.

IF and when the CYA drops to 20 ppm because of splashout then bump it back up to 30 ppm by going back to dichlor.

IF your test kit only goes down to 30 ppm on the CYA then bring the initial CYA to 40 ppm and bring it back up when it hits 30.

IF you slightly overshoot your target don't stress,. Just maintain your FC in the 4 to 6 ppm range for a CYA of 30 to 50 and a 3 to 5 ppm range for 20 to 30. IMHO, the 4 to 6 ppm is more desirable given the high bather to water ratio in a tub vs. a swimming pool.

Shock when combined chlorine is over .5 ppm. If you have persistent CC over 1 ppm then shock with MPS weekly AND leave the spa uncovered to allow volatile oxidation byproducts to gas off.

This is the dichlor/bleach method simplified.