Pool Opening - Amount of Chlorine Needed to Shock

[PoolGai]

Hey All,

I probably won't open my pool until the 3rd week in May and will be adding some bleach in the water until then, since the outside temps are getting warmer, but my question is this:

When I do open, based on my CYA level (~50) it says I should be shocking to '15' which is almost 933oz. of bleach - isn't that excessive? In the past, I've opened the pool to find a lot of green algae, primarily because it got warm and I have a mesh cover, and have added about 6 1lb. bags of shock. I'd prefer to use just straight Chlorox this year, but am struggling finding out how much I should really add, despite having algae or not. Any suggestions?

And, do I also need to add algaecide or not when opening since I added it when I closed the pool?

I'm just trying to get all my ducks in a row and make sure I have all of the proper chemicals before opening time rolls around.

My understanding is to 1) adjust pH & CYA levels then 2) shock.

Thanks,
Z

 

[JasonLion]

It appears you have done your calculations correctly. 6 lbs of 65% cal-hypo will raise FC by close to 15 in 30,000 gallons. 933 oz of ordinary 6% bleach will also raise FC by close to 15 in 30,000. It does take much more volume of bleach to have the same effect as the powdered/granular forms chlorine.

There isn't really any point in using algaecide when opening. Algaecide is most effective at preventing algae, and not very useful when you already have algae. That is the main reason why you use it when closing, but not when opening.

 

[PoolGai]

Makes sense, the bleach is still cheaper but raises the pH a bit...I'm not sure what I'll go with, just making sure my logic was correct. Thanks for your help.

 

[jblizzle]

I was under the impression that bleach had little long term affect on the Ph. It may go up initially but then drops back down as the bleach is "processed ".

 

[anonapersona]

Most importantly, you may need that dose as calculated for the first dose, but then you need to retest the FC and keep the level up in the hours after the first dose circulates and gets used up against the algae.