Drop my shock level?

[bwiley47]

This is my 3rd year doing BBB and I thought I had it figured out...but guess I was wrong. Once again, I've had multiple issues this year, so pool is still not clear.

I have been shocking to clear it. (last week the filter was not hooked up properly so I don't count that week). On 7/3 my cya was 35-40, been using a shock level of 16. We let the kids swim since the 4th, had to add a little water from splashing on the 5th, hard rain yesterday morning. This morning I check my cya and it is 20. I'm figuring I lost some from the rain and add.

I tested FC at 2pm yesterday and added to reach 16. Did not recheck until 830pm since the kids were swimming from 6-8. At 830pm it was 11.5. This am my FC is 16.5.

With 4 swimmers x2 hrs and 6 hrs of sunlight, is that an appropriate FC loss? Or is my cya test this morning probably accurate? Do I let my FC go down to 10 till I can add cya? My liner has some discoloration in the pattern at 1 end, so I don't want to do any more damage.

Thanks again for all of your help. (I know I've been a problem child this season)

 

[duraleigh]

At 830pm it was 11.5. This am my FC is 16.5.

FC (chlorine) cannot go up unless you add it to the pool....it can only go down. You have some testing errors and seem to be mixing CYA and chlorine issues in the same sentence. I am confused.

 

[bwiley47]

Sorry. I added 143 oz of bleach at 830pm to reach 16. (Didn't retest after since I'm low on reagent). Then when I tested this morning it is 16.5.

7/3 cya 35-40 Changed shock level from 10 to 16.
7/5 Added approx 1/2 - 1 inch of water.
7/6 Hard rain for about 1 hour
7/7 cya 20

7/6 2pm added bleach to reach FC 16
830 pm FC 11.5 added bleach to reach 16 (is my cya reading of 20 this morning probably correct with this kind of drop, or is the drop probably appropriate given the sunlight and swimming?)

7/7 9am FC 16.5

 

[frogabog]

Rain wouldn't lower CYA that much, that fast. 40-20ppm is a 50% drop. You'd have to drain half the pool and refill to get this result.

Retest CYA, make sure to mix for at least 30 seconds and then re-pour into the tube many times to verify results.

It rains all the time here, I have lost no CYA due to rain. Even draining and refilling about 15% made little change, maybe 5 ppm but hardly.

Looks like you lost little or no chlorine overnight, and you just over dosed a tad last night.

 

[bwiley47]

That's a good point about the 50% drop. I will retest my cya. My biggest concern is if I misread on 7/3 that my cya was 40 and I have been using a shock level of 16, what have I done? At one time this week I overshot to FC 18! And the kids have been swimming. We have not noticed any skin irritation so that's a good thing!

Well, it is what it is. So I guess I'll just retest my cya and shock accordingly.

Thank you.

 

[zea3]

Make sure the pump has been running around an hour before you test.

 

[bwiley47]

Yea, it's been running 24/7 while shocking. Although, that may have been my problem sunday when I checked it since we had a problem with the pump that day. I was pretty confident with my reading that day.

Rechecked my cya, twice. It's 20.

I guess the good thing is I won't have to worry about adding bleach today!

Wondering how high above your shock level do you have to go before it causes damage?

 

[frogabog]

I wouldn't know, but based on mustard shock for 20cya you have only been 2-2.5ppm above that in the first place. Imagine if you overshot mustard shock level by 2ppm for a few days, would you be quite as concerned?

I don't know, but I'd probably placate myself with such a fantasy and move forward, either leave cya where it is for a while and use less bleach or add cya and go back to 16ppm shock. shrug...

 

[bwiley47]

Again, another good point. Hadn't really thought of it that way. (Oh, this mid-life brain fog is driving me crazy)

So, according to Chemgeeks shock level for mustard algae with cya of 20 it's 12.7 and Jason says the FC test can be off +/- 1.5, and I tested as high as 18 one day, I could have been as high as 19.5 and as low as 16.5. (For a short period of time).

My goal was 16, but I've actually had a hard time keeping it there, it's been averaging 14, 11.5... except overnight I was able to maintain.

Overall, this makes me feel some better. No use crying over spilled milk!

 

[frogabog]

Fantasize that the pool calculator is right too, enter 20 CYA and the mustard shock is 14. Feel better?

Fantasies are awesome that way sometimes... Works to clear the brain fog. :~}

 

[bwiley47]

oh now your just being mean! :lol: (Didn't know mustard was on the pool calculator) hmm.


Thanks. Feel alot better......as far as the pool goes anyway.