Combined chlorine increased after shocking? Please help, I’m new to this!

[JGhottub]

Hello. I am new to this forum and also a fairly new hot tub owner. I am having trouble with my chlorine levels, specifically getting rid of combined chlorine. For the first couple months I was just using non-chlorine shock and a chlorine floating thing. After doing more research I realized I should also be using chlorine shock. So last night my FC was at 5.0 and by CC was at 1.2. I threw in 2 Tbs of Dichlor (that’s how much the instructions said to use to get my FC to 12) and left the jets on and lid off for an hour. 12 hours later I tested it and my FC is at 11.2 and CC is 2.4. Why has my CC doubled?  I thought the shock was supposed to kill it?

[Jackbt]

I’m roughly in the same boat can’t get rid/lower the combined chlorine.  I haven’t come across any helpful answers as I’ve research hopefully someone has some ideas.

[Splashman]

Hi Jghottub,

I think you might have your reading wrong. There is 3 different factors when reading Chlorine.

"FC" Free Chlorine

"TC" Total Choline 

"CC" Combined Chlorine

When you are testing your water with a reagent test kit using drops. You are testing FC & TC. The CC is what you get when you subtract the two together. For Ex....

FC = 2.0  TC = 3.0  : CC = 1.0

Now the problem you are having is your not reaching "BREAKPOINT". This is a chemical term used in the pool and spa industry that allows you to overcome the CC levels in pools and spas.

The formula is a little more complex because you need to know the chemical numbers to match up. But here is the basics

TC - FC = CC

CC x 10 = Desired Free Chorine Level

Desired Level - Existing free Chlorine = Adjustment 

Now that we have the basics lets get more complex.

(A) Amount of chemical indicated by label   x   (B) Actual spa volume /(B2)Divided by product label gallons (most say 300 or 500 gallons) = (b3)  x (C)Desired chemical Change aka adjustment / Divided by Product label by PPM (usually 1ppm) = (C3)

(A)  x (B3) x (C3) = your number

 

If you do not put the right amount to over take the CC you will always fight the ever climbing CC.

I hope this gets the wheels turning for you. It seems over whelming but it is not. But you know you can just wing it and just always add more than what your gut tells you. One thing to note is to make sure you leave your hot tub uncovered so the chloramines which is the CC burning off don't bake the underside of your cover. Give it like 30 min. Also anything over 10PPm in Chlorine is unsafe to bath in. 

Good Luck

 

[RDspaguy]

Non chlorine shock will work, but give a false high chlorine reading for days. If your spa has an ozone system you should not need to shock, as ozone provides oxidation and will reduce tc, then fc. 

I would recommend you get rid of the floaty thing and the tablets that go in it, as they are trichlor, or even worse bromine, which is the reason you battle ph. Use 1 tsp plus 1/2 tsp per additional person of dichlor after you use the spa, at least 2 tsp per week if used infrequently. Leave cover open for 30 minutes after you add dichlor to extend cover life. Shock with dichlor or non-chlorine shock each week. It should not take much. You will find you seldom have to adjust your alk and ph, your cover and pillows do not bleach out, your cover lasts longer, your topside controller lasts longer, you do not smell chemicals when you open your spa, you don't itch after using your spa, and you enjoy owning a hot tub more than ever.

The use of a mineral purifier adds silver and copper into the water which interferes with the reproductive cycle of single celled organisms such as bacteria and algea. It does not actually sanitize or destroy organic contaminants so is not a substitute for chlorine, it just slows down multiplication. This can be helpful for those who struggle with water chemistry.