Frustating Green Pool

May 16, 2010
St. Louis, Mo.
My pool is has been green for a week now coming back from vacation. I've adjusted the chemicals, but the pool is still green. My readings from 10 minutes ago is. Should I add more bleach?
CC- 5
FC- 5
PH- 7.8
TA- 120
CH- 160
CYA- 50


TFP Expert
LifeTime Supporter
In The Industry
May 20, 2007
SWSuburban Chicago, IL
FC + CC = TC so if your CC is indeed 5 then you have a problem.
Looks like you may be testing with a DPD test - you need an FAS-DPD test - which is easier to determine CC counts and also can test FC up to 50ppm - and since your shock level is 20, your test won't go that high....

You need to shock the pool, and purchase an FAS-DPD test.

Shock until the FC holds overnight
the CC is .5 or less
the water is crystal.
Jun 28, 2009
North Texas
1. Go to and plug in your existing values in the "now" column;

2. In the last row "Suggested Goal Levels" select "" in "Use suggested goal levels from:"

3. Select "Bleach" for "Primary source of chlorine"

4. Select "Fiberglass" for pool surface

5. In "Target" column for FC select 16 (this is the recommended value for Shocking based on your CYA levels - see recommended FC levels in second to last row)

6. In the third column in the "FC" row set to your bleach %/jug size. In my case I get big ultra bleach jugs from Sams so it's 6% bleach/182 oz. Yours might be different. Float your mouse over the "Add 319 oz" and it will show you how many gallons (or jugs) to add in the white field. For you it's 2 gallons 2 quarts or 1.8 (182 oz) jugs."

7. Add this amount to your pool at night with the filter running (run 24/7 until process is done). Next morning retest (using a Fas DPD kit - see this link: The Fas DPD measure is the only way to test chlorine higher than 4 or so. If you don't have it it's almost a waste of time to shock although you could try if you don't have it and just shock until clear).

8. Go back to Repeat above steps, adjusting the "Now" column to reflect the morning's pool read. Add the amount of chlorine to get it back to 16.

9. Repeat the prior step at night. Repeat this procedure morning and night until the pool is clear. When it is clear, at night test again an hour after you put in whatever chlorine you need to get it back to the shock level. Next morning test again - if the difference between the morning's test and the previous night's test is 1 ppm or less you are done. Otherwise keep shocking morning and night until your difference is 1 ppm or less.

10. Read these for background and reference:
and generally:

11. My experience has been that the key is shocking to the shock level recommended by the pool calculator based on the CYA. If you don't have the CYA plugged in right or don't consistently shock to the level recommended based on the CYA (in this case 16) even if it seems high, you will spend endless days and $$ and chlorine trying to get the pool clear. Bite the bullet and put in the high levels of chlorine up front, keep it to that level until done, and you will get a clear pool.

12. I would recommend getting the PH down to 7.2 also before shocking as low ph helps to make the chlorine more effective.

13. When done, keep the chlorine at the regular non-shock level recommended by the poolcalculator.
May 16, 2010
St. Louis, Mo.
I will do all this and thank you for your help. It never has gotten this bad before. The test kit I have is a Taylor. I wonder if the hot weather in the 100's mix with 15minute down pours of rain every other day has something to do with it?