Chlorine & pH Control

[karrde97]

I have a 21' AG and run the pump 24/7 and have sun 24/7. I'm trying to determine a trend so I know how much to add each night. CYa=40-50.

Last night:
Cl=.5
pH=7.8

I added 3 cups bleach(skimmer) and 2 cups acid(return) at the same time.

This morning:
Cl=1
pH=7.5

Does the acid eat up Cl when I add them at the same time? Should I bump up my CYa? I put in 1 Qt of bleach last week and the Cl went from.5 to >5.5.

[aylad]

The acid does not eat up the chlorine...if you've had Cl of .5 with a CYA of 40-50, then chances are you've got something blooming in the water that's causing the Cl demand. With a CYA that high, you need to always keep it above 3. I would try shocking the pool, let the cl drift back down to the 4-5 range, and then figure your consumption from there.

Janet

[duraleigh]

Download bleachcalc for your dosage requirements. Assuming your pool is about 13.500 gallons, one quart of bleach (6%) will raise your Cl level 1 ppm

Acid should have little affect on your Cl test results.

and have sun 24/7.

Someone has moved Peoria a lot further North from where I remember!

[chem geek]

First of all, your chlorine level is much too low (you said it was .5 at night, then you added chlorine, and then 1 the next morning). Refer to Ben's Best Guess CYA Chart to see that at 40-50 ppm CYA you should have a minimum of 3 ppm of chlorine at your lowest point which is just before you add chemicals if you are only going to add once per day. With full sun (you said 24/7, but you're not north of the artic circle so I'll assume you didn't really mean that) you will lose perhaps half of your chlorine so you'll probably have to add chlorine to get to 6 ppm though you'll have to check this and just make sure you don't go below 3 ppm.

The suggestion to use BleachCalc is the way to go. You are probably adding way too little chlorine.

Richard

[karrde97]

My bad. I was thinking 1qt = 6ppm. I must have put in more than 1qt last week to get it to shoot up so high. I was waiting for the Cl to drop but we some dark days and then it drop like a rock on the sunny day. Now I'm trying to get it back up. I just miscalculated a little.

When you say shock, bring the Cl up to 10-15ppm range?

[chem geek]

I just reread your post and you say that last week you added a quart (4 cups) of bleach and your chlorine went from .5 to >5.5, but from last night with the chlorine at .5 you added 3 cups of bleach and this morning the chlorine was only 1? And the only difference was that you added acid at the same time as the bleach? Unless you have a rather small pool, adding a quart (4 cups) of bleach is not going to have you raise the chlorine by over 5 ppm.

The other posts are correct that adding acid and bleach do not cause a problem unless you mix them together (even pouring them in the same area of the pool) because doing so would be very hazardous as you could produce chlorine gas. Maybe where you poured your acid it migrated over towards the skimmer, but I doubt that. You can always just try adding the chlorine to the skimmer first, wait a few minutes, then add the acid near a return. If this makes a difference, please let us know. That would be interesting!

What kind of chlorine test are you using? Perhaps one of your measurements actually had a lot of chlorine, but was bleached out (this can happen with the DPD test, but not the OTO or FAS-DPD tests).

Richard

[chem geek]

My bad. I was thinking 1qt = 6ppm. I must have put in more than 1qt last week to get it to shoot up so high. I was waiting for the Cl to drop but we some dark days and then it drop like a rock on the sunny day. Now I'm trying to get it back up. I just miscalculated a little.

When you say shock, bring the Cl up to 10-15ppm range?

OK, that's more like it. Sorry I didn't read your correction before I sent my response. Never mind about the chlorine test kit question.

[karrde97]

I'm using Ben's kit.

I'm kind of in flux since I've been trying to lower my Alk. Now I'm trying to get everything back to normal. I'm going away for a week or so next month and I want be able to tell my wife what to add every night in hopes of maintaining some normal level until I get back.

[chem geek]

Can you download bleachcalc as Dave (duraleigh) suggests? It can be found at BleachCalc. That's the easiest way for you to figure out how much of each chemical to add.

[karrde97]

I downloaded it awhile. I was thinking 1 qt = 6ppm instead of 1 gal. I'll just have to restart tonight.