How much chlorine should I be adding a day?

[New and confused]

This is my second year of owning our pool and the TFP method has been great. I am just wondering if I have been adding too much chlorine. I was reading an old thread on this topic and heard anywhere from every day to once a week. I have been adding about 1/2 a gallon of 8.25% bleach every day. My cya is about 25 so I am trying to keep my FC at 4, but I lose some during the day. I usually add my bleach at night and then by the next night I am down to 4 again. For example last night my FC was 3.5 and I added about 6 cups of bleach. This morning it was 7.5, so I didn't add any more and when I checked at 630pm my FC was 4. My ph has been between 7.5 and 7.8. When I was in the pool today, my skin seemed kind of dry ( another reason I was wondering if I have been adding too much chlorine).

Any advice is appreciated.

 

[jblizzle]

Telling us cups is not as helpful as telling us the ppm you added or targeted.

You need to daily add enough so the FC never falls below the minimum for your CYA. Raise your CYA and you will lose less to the sun.

 

[chem geek]

If your pool is exposed to sunlight, then your CYA level should be higher, but probably not above 50 ppm. You could raise it to 40 ppm and see how much chlorine you use (in ppm FC per day).

Your FC/CYA ratio is higher than we recommend in the Chlorine / CYA Chart so is probably why you are noticing the effects of chlorine more.

Generally speaking, you need to add chlorine every day (perhaps two if the pool is not in full sun) unless you have a pool cover that is mostly opaque to the UV in sunlight. In that case, you may be able to add chlorine twice a week (that's my situation, for example). Adding only once a week would not normally work well as you'd have larger swings in chlorine level so in the days after dosing you may notice chlorine's effects more and not like that. Most people on this forum add chlorine daily. It's just a simple routine and minimizes the amount of chlorine both in usage and in absolute level.

 

[New and confused]

I thought I might have to add more stabilizer to increase my CYA, but then I'm adding more chlorine, right? So why wouldn't I keep it where it is? Also the ppm (points per million?) is kind of hard for me to wrap my head around. Is there a place I can read more about this? I just look at pool math and it tells me oz and cups/quarts. That's why I referred to it in my post, sorry.

 

[jblizzle]

So what FC level are you targeting every time? That is what I want to know because then we can see how much it is dropping.

At a higher CYA level, while the FC level might be higher, you should lose fewer ppm of FC to the sun.

 

[Richard320]

This is my second year of owning our pool and the TFP method has been great. I am just wondering if I have been adding too much chlorine. I was reading an old thread on this topic and heard anywhere from every day to once a week. I have been adding about 1/2 a gallon of 8.25% bleach every day. My cya is about 25 so I am trying to keep my FC at 4, but I lose some during the day. I usually add my bleach at night and then by the next night I am down to 4 again. For example last night my FC was 3.5 and I added about 6 cups of bleach. This morning it was 7.5, so I didn't add any more and when I checked at 630pm my FC was 4. My ph has been between 7.5 and 7.8. When I was in the pool today, my skin seemed kind of dry ( another reason I was wondering if I have been adding too much chlorine).

Any advice is appreciated.

Believe it or not, you're doing it right. You're adding enough bleach so that it's still above the minimum for your CYA when you add more. You're not letting it dip below too often or for too long.

I'd suggest you run all the tests on your water. Eye irritation and dry skin are more likely from Combined Chloramines or pH out of whack than the amount of free chlorine you've been maintaining.

It's probably time to go back to pool school for a refresher course.
ABCs and Recommended Chemicals and Poolmath are probably the best ones to start with.

 

[New and confused]

Thanks Richard, I did read all 3 of those (plus a few others) just to be sure I knew what I was talking about. In response to Jblizzle - I have been targeting FC of 4, so I add more at night to counteract my loss during the day. Here are my numbers as of 645 pm today:
FC 4
CC 0
ph 7.7
CYA between 20 and 30 (last time I checked was yesterday at 700 am)
TA 140 (as of yesterday at 700 am)

 

[chem geek]

I thought I might have to add more stabilizer to increase my CYA, but then I'm adding more chlorine, right? So why wouldn't I keep it where it is? Also the ppm (points per million?) is kind of hard for me to wrap my head around. Is there a place I can read more about this? I just look at pool math and it tells me oz and cups/quarts. That's why I referred to it in my post, sorry.

You don't actually use more chlorine with a higher CYA target in spite of the higher FC minimum level, at least not for a pool exposed to lots of sun. The reason is that CYA shields chlorine from breakdown (in addition to binding to it) and that effect is so strong that one would lose less absolute FC with 4 ppm FC and 50 ppm CYA than they would with 2 ppm FC and 25 ppm CYA. Of course, as you point out you need to add more than being at the minimum so that you end up at the minimum the next day, but you will lose less FC at higher CYA levels.

You say you are targeting a minimum FC of 4 ppm with your CYA of 25 ppm but PoolMath says for that CYA that the FC Goal is "2 to 6" assuming you set "suggested goal levels from:" to "troublefreepool.com" and set "Primary source of chlorine:" to "Bleach". So even with the larger swings you have due to losing more from sunlight you're on the higher side of that range. If you had a higher CYA level, say for example 40 ppm, then you might go from 5 to 3 or if you were at 50 ppm CYA you might go from 6 to 4 (and you may lose less than this amount). Though this sounds about as high as your current situation, it isn't in terms of effects on your swimsuits, skin, and hair because the active chlorine in the water is proportional to the FC/CYA ratio (see the Chlorine / CYA Chart). So today you have a minimum you have set of around 4/25 while what I am describing has a minimum of 3/40 or 4/50 which is half the active chlorine you have now but is still at or above the minimum needed to prevent algae from growing.

 

[woodyp]

That "target" number is arbitrary given varying pool conditions. "target" whatever number you lose in ppm of FC daily to stay above your minimum for your given level of CYA. I'd get that CYA level to 40 or 50.

 

[New and confused]

Thanks everyone. I'm going to get more stabilizer today and will get back to you when my cya is 40.