Shock or not?

[peloncito]

I have a SWG, pebble pool that looks great and the water is crystal clear, however..... when I test my FC & TC there is enough of a discrepancy towards the higher TC level that makes me think I should shock the pool according to my "The Pool Calculator". Basically it says that if my CC is above .5, which I believe it is, I should shock the pool based on the Pool Calculator recommendation of a shock level of 11. What I need to know is for how long? I just started adding CYA so my levels are relatively low (see below). Oh yeah, I just started using the BBB method with absolutely great results but I am still a newbie to this whole thing. I have had my pool for about three years and I have never shocked it. I have changed about 1/2 of the water once so far.

Advice is very much appreciated.

Mike

Pool Size: Apprx: 20,000G
FC= 2.0, TC = almost 3 which should translate to CC being higher than .5 (time to shock?)
pH= 7.6
TA= 80
CH= 280
CYA= 20
Salt= 3400
Temp= 76° (pool is in Mexico)

 

[polyvue]

Hello Mike, Welcome to TFP :-D

What kind of test kit are you using to determine FC, TC etc? In spite of the clear water if the CC is definitely above .5 ppm I would shock the pool. A constant 12 ppm FC level should work in view of such a low level of CYA. Shouldn't take long to get those combined chloramines down -- maybe just a day.

Here's an excerpt from Pool School that may prove informative:

Shocking:

• 1. Measure the FC level
  2. Add enough chlorine to bring FC up to shock level
  3. Repeat steps 1 and 2 as frequently as practical, as often as once per hour, and not less than twice a day, until:
  [list:5npspmx5]a. CC is 0.5 or lower;
  b. An overnight FC loss test shows a loss of 1.0 ppm or less;
  c.And, if you don't have a FAS-DPD test kit, the water is clear

[/list:u:5npspmx5]

• Source: Shock Your Pool