To shock or not to shock? That is the question.

WestSidePool

Well-known member
Jun 14, 2009
424
Cincinnati, OH
I took a reading on Tuesday evening and CL needed to be added.
I put in 1 gal of 10% CL. That brought me up to 6 ppm.

I checked the levels again last night about 7:30pm and my CL level was at 1 ppm.
So I added another 1 gal of 10% CL.
I checked the levels again about 10pm and it was at 8 ppm.

(Doing overnight FC loss check)

This morning at 6:15 I checked the levels and my FC is at 6.5 ppm. So it looks like i'm losing CL over night.

The water is crystal clear and I do not see any visual signs on algae yet.
Is it necessary to shock?

Total numbers for Wed Evening and Thursday morning.
Wed:
FC 8
CC 0
PH 7.5
TA 70
CYA about 50

Thurs morning:
FC 6.5
CC 0
PH 7.5
TA 70
CYA about 50
 

Bama Rambler

Mod Squad
TFP Expert
Bronze Supporter
LifeTime Supporter
Jun 22, 2009
23,391
SouthWest Alabama
First a little correction and then on to your problem! :)

We normally refer to chlorine around here as either FC or CL. CH is Calcium Hardness to us so when you use it for Chlorine it's a little confusing to us. I know it's a petty thing but if you don't mind using CL or FC in the future I'd appreciate it.

Now to the real issue. Since you apparently lost 1.5 ppm FC overnight I'd say you need to shock. Your shock level for a non-SWCG pool with a CYA of 50 will be 20ppm. You need to add enough Chlorine to get you there and the more consistantly you can hold it there the faster you'll be done shocking. Test and add as often as every hour if you can.
 

WestSidePool

Well-known member
Jun 14, 2009
424
Cincinnati, OH
I knew CH didn't seem right for chlorine, but that's what kept popping in my head. I changed it in my above post.

Since I work 7-4 weekdays do you suggest I wait till the weekend to start the treatment processes, since I wont be able to keep up with the hr adding/checking on the weekdays?
Or do you think I should be fine to start it at 4:30 when I get home and it should be alright to do the FC loss test tonight into tomorrow morning?
 

Bama Rambler

Mod Squad
TFP Expert
Bronze Supporter
LifeTime Supporter
Jun 22, 2009
23,391
SouthWest Alabama
I'd start tonight and test and add until you go to bed. Then check and add in the morning and again when you get home. It isn't quite as good as hourly but you'll be making good progress against it and maybe it'll only take a day or two to be done. The good thing about doing it before you go to bed and as soon as you get up is that you're automatically doing the overnight test every night so you'll know immediately when you're done shocking.
 

anonapersona

TFP Expert
LifeTime Supporter
Nov 5, 2008
2,598
The other thing is to brush everything really well.

I recently found that the boulders that are set as coping around the pool, very rough surface, were growing algae above the water line. Pool was fine but that algae was consuming chlorine with every splash of water or drop of rain. I scrubbed them off with a 50% bleach solution and now chlorine usage is back to normal.