Help with appropriate shock for vinyl in-ground

[aylad]

In a 25K gallon pool, each 2 gallons of 6% bleach will raise your FC by 5 ppm, so you can use that as a guide. As to how high your chlorine needs to go, that will depend on your CYA level. If you can see the blue links at the bottom of Watermom's sig, click on the "best guess chlorine" table to tell you how high your Cl needs to go, based on your CYA level. You can absolutely shock with bleach and still use your tabs in the floater, IF your CYA level is not too high--most folks keep it around the 40 ppm range.

Janet

[jeepers]

In a 25K gallon pool, each 2 gallons of 6% bleach will raise your FC by 5 ppm, so you can use that as a guide. As to how high your chlorine needs to go, that will depend on your CYA level. If you can see the blue links at the bottom of Watermom's sig, click on the "best guess chlorine" table to tell you how high your Cl needs to go, based on your CYA level. You can absolutely shock with bleach and still use your tabs in the floater, IF your CYA level is not too high--most folks keep it around the 40 ppm range.

Janet

Thanks, Janet.

Here are my numbers from 6/24:

FC 1.5
TC 1.5
CC 0
pH 7.7
Hardness 230
Alk 83
CYA 25
Copper 0.1
Iron 0

I brought the ALK up slightly after this test. I use 3" tabs in a floater and shock every 7-10 days with Calcium Hypochlorite.

I'll review the Best Guess chart again this evening. I looked at it briefly at work today but wasn't quite clear on how to read it so I'll see if it makes more sense now.

Jim

[aylad]

Why do you shock it so often? Unless you're having a problem, see algae starting, or are losing chlorine overnight, there's really no reason to shock it on a regular basis. However, with your CYA at 25, you need to keep the chlorine between 3 and 6 ppm at all times. Be careful about shocking with the cal-hypo, though--your calcium level is climbing, and it won't be too much longer before you start having cloudy water issues due to the calcium....

With the best guess chart, the left-most column shows your CYA level, the next one shows the minimum and maximum chlorine levels that you need to keep in your pool for that CYA level, and the next column shows how high you need to take your chlorine to achieve "shock" level. The right-most column is for those who have mustard or black algae, or some other water problem that does not respond to normal shock levels.


Janet

[jeepers]

Why do you shock it so often? Unless you're having a problem, see algae starting, or are losing chlorine overnight, there's really no reason to shock it on a regular basis. However, with your CYA at 25, you need to keep the chlorine between 3 and 6 ppm at all times. Be careful about shocking with the cal-hypo, though--your calcium level is climbing, and it won't be too much longer before you start having cloudy water issues due to the calcium....

With the best guess chart, the left-most column shows your CYA level, the next one shows the minimum and maximum chlorine levels that you need to keep in your pool for that CYA level, and the next column shows how high you need to take your chlorine to achieve "shock" level. The right-most column is for those who have mustard or black algae, or some other water problem that does not respond to normal shock levels.


Janet

Thanks again, Janet -

So to confirm that I'm understanding the Best Guess chart, assuming that my FC is 1.5 and if I round my CYA up to 30, would I add approximately 5 gallons of 6% bleach to achieve an acceptable "shock" of 15 ppm?

For my current practice, my local store recommended shocking 1x/week with the Calcium Hypochlorite. I've extended it to once every 10 days or so but now realize that even this may be overkill. The kids are in it literally every day so I've been trying to avoid getting behind the 8-ball with the chemicals.

Another question: the pool store told me to keep the FC between 1-3ppm. They didn't seem concerned about the CYA so long as my FC level stayed within reasonable limits. Should I be keeping it higher?

Jim

[PoolDoc]

The Best Guess page -- linked in my signature -- answers most of the questions you asked. Read it, and then we'll try to answer those that remain.

[Watermom]

Also, trichlor pucks are stabilized which means they add CYA. So, if you are going to continue to use them, you'll need to check your CYA every week or two. For every 10ppm of chlorine that the pucks add, they also add 6ppm of CYA. When your CYA hits about 50, you'll need to stop using them or your CYA level will get too high. At that point, just use bleach for your daily chlorination needs as well as shocking when necessary. (I rarely shock my pool. As long as you don't let your cl level fall lower than the minimum on the range listed in the Best Guess chart, you shouldn't need to shock.)

[SalemCastles]

Hi Jim,

Where about's are you and how much sunshine does the pool get per day?