For real, what's going on with my chlorine level?

[hawkmoon7]

So the problem is back... I'm at a loss...

Pool water looks like crystal. Temp at 87. Sunny Florida, screen enclosed pool.

SWG set to 100% running 14 hours a day. (It's a Pentair rated for 40,000 gallons, my pool is 17k). It is working... returns produce bubbles and water tested from the returns shows elevated chloring levels. SWG is clean.

FC at 2.5 CC at 0 to maybe .5, but really close to zero. CYA at 95. TA at 100. PH 7.2-7.4. I have borates. Salt within range.

So every other day, I add 50oz of 11.5% liquid chlorine to get my FC up to 5ppm. About 48 hours later, I'm near 2ppm. Overnight chlorine loss seems nil., maybe .5, but hard to tell. I have noticed that the OTO test looks like maybe .5ppm, but if I let it sit for a few minutes, the yellow deepens to the 2.5 range. The drop test confirms 2.5ppm. I can't explain why my SWG can't keep up at 100% when neighbors with similar pools run theirs at 60% for 12 hours and I'm at 100% for 14 hours.

Before I raised the CYA to that level, I slammed it. Chlorine kept right at SLAM level for a few days, then I it fell (quickly) to around 12, and then it took about 2 weeks to drop to 2. SWG at 100% the whole time. Now it's back to every-other-day chlorine additions.

I swear, I'd get a second SWG if my system allowed it. This is driving me crazy. I can't think of any other x-factor. I do have a lot of water features, but seldom use them. Variable pump is running at around 1600 rpm.

 

[Bperry]

So the problem is back... I'm at a loss...

Pool water looks like crystal. Temp at 87. Sunny Florida, screen enclosed pool.

SWG set to 100% running 14 hours a day. (It's a Pentair rated for 40,000 gallons, my pool is 17k). It is working... returns produce bubbles and water tested from the returns shows elevated chloring levels. SWG is clean.

FC at 2.5 CC at 0 to maybe .5, but really close to zero. CYA at 95. TA at 100. PH 7.2-7.4. I have borates. Salt within range.

So every other day, I add 50oz of 11.5% liquid chlorine to get my FC up to 5ppm. About 48 hours later, I'm near 2ppm. Overnight chlorine loss seems nil., maybe .5, but hard to tell. I have noticed that the OTO test looks like maybe .5ppm, but if I let it sit for a few minutes, the yellow deepens to the 2.5 range. The drop test confirms 2.5ppm. I can't explain why my SWG can't keep up at 100% when neighbors with similar pools run theirs at 60% for 12 hours and I'm at 100% for 14 hours.

Before I raised the CYA to that level, I slammed it. Chlorine kept right at SLAM level for a few days, then I it fell (quickly) to around 12, and then it took about 2 weeks to drop to 2. SWG at 100% the whole time. Now it's back to every-other-day chlorine additions.

I swear, I'd get a second SWG if my system allowed it. This is driving me crazy. I can't think of any other x-factor. I do have a lot of water features, but seldom use them. Variable pump is running at around 1600 rpm.

You need way way more chlorine than 5ppm if your CYA is really 100ppm. You should be targeting closer to 14ppm. But OCLT that overnight chlorine loss doesn’t make sense. Why is is hard to tell the result? The FAS DPD test is pretty clear cut. Youde be wise to ignore that OTO test as it’s isn’t very accurate with the level of chlorine in the water.

 

[Mdragger88]

Are u doing the Overnight Chlorine Loss Test with fc at target level for your cya? (At least 7ppm) FC/CYA Levels also you should be using the fas/dpd for the oclt.
In general u are maintaining too low of a fc level for your cya level so it would not be surprising if you have nascent algae. An oversized swg can hide a problem like this for longer than most but it will never overcome algae.

 

[hawkmoon7]

I literally just came off of a slam... then I raised CYA to 90 (I slightly overshot to 95 I think). I keep raising the Fc level to 6-7 (as per the SWG/chlorine chart) at night and before doing the overnight chlorine loss test. I don't really lose any chlorine at night, and I don't have much in the way of CC if at all.

The OTO test is hard to read for me, and with the high CYA, I noticed the yellow deepens over a few minutes. The drop test is easy, but I'm testing every day, sometimes twice of day because of how much chlorine gets used up. I'm testing daily and adding chlorine at least once every 2 days. I'll go raise it to 7 now. But it won't last.

I also noticed that if I leave the sample in the OTO comparitor for about an hour, it turns clear again.

I buy about 3-4 gallons of 11.5% liquid shock a week. For months. The only relief I had was in December when I turned the heater off and temps fell to 75 in the pool. SWG at 40% kept levels fine. NOw that the temp is back to 88 to 92 in the water, I can't maintain it. (88 for pool, and occasionally 92-94 in attached spa).

Should I supplement with an algeacide maybe?

 

[hawkmoon7]

Here are some photos in case I'm missing something. The wall plaster is blue with some green flecks in it, so it is hard to tell the true color. It's also a bit cloudy today.

 

[Bperry]

I literally just came off of a slam... then I raised CYA to 90 (I slightly overshot to 95 I think). I keep raising the Fc level to 6-7 (as per the SWG/chlorine chart) at night and before doing the overnight chlorine loss test. I don't really lose any chlorine at night, and I don't have much in the way of CC if at all.

The OTO test is hard to read for me, and with the high CYA, I noticed the yellow deepens over a few minutes. The drop test is easy, but I'm testing every day, sometimes twice of day because of how much chlorine gets used up. I'm testing daily and adding chlorine at least once every 2 days. I'll go raise it to 7 now. But it won't last.

I also noticed that if I leave the sample in the OTO comparitor for about an hour, it turns clear again.

I buy about 3-4 gallons of 11.5% liquid shock a week. For months. The only relief I had was in December when I turned the heater off and temps fell to 75 in the pool. SWG at 40% kept levels fine. NOw that the temp is back to 88 to 92 in the water, I can't maintain it. (88 for pool, and occasionally 92-94 in attached spa).

Should I supplement with an algeacide maybe?

Why did you raise the CYA to 90+? The app says that’s the top of the tolerable range, but ideally is 70-80. The FC level needs to be maintained always above 5ppm, never ever less. That’s why your target should be 14ppm. If you lose 4ppm due to normal daily use, the day ends with 11ppm which is decently above 5ppm.

If you are only raising it to 7ppm, losing 4 in a day easily brings you under the minimum which is why you may be growing algae. Did complete the SLAM with all three passing criteria? How did you do it with that level CYA?

 

[duraleigh]

Back to the basics.....Only two things consume chlorine in your pool Sunlight and organics in your pool water.

I think you have a cover of some sort over your pool so the sunlight factor is absolutely minimized. It leaves you with an inescapable fact.......you have organics in the pool and a SLAM needs to be done.

Your CYA at 90-100 makes the SLAM almost impossible which is why I NEVER like the idea of exceeding 80 ppm on CYA and, even then, approaching 80 very carefully

 

[hawkmoon7]

Back to the basics.....Only two things consume chlorine in your pool Sunlight and organics in your pool water.

I think you have a cover of some sort over your pool so the sunlight factor is absolutely minimized. It leaves you with an inescapable fact.......you have organics in the pool and a SLAM needs to be done.

Your CYA at 90-100 makes the SLAM almost impossible which is why I NEVER like the idea of exceeding 80 ppm on CYA and, even then, approaching 80 very carefully

I guess so. It's just so odd. I always kept CYA around 50 to 60. I've slammed at least 4 times in the last year. Out of desperation, I raised CYA to 90 to try to keep the chlorine in. I've only been at this high CYA very recently.

I guess it is organics. Even when I slammed a few week ago, the CC were nil though. Water always clear. But it HAS to be going somewhere. I'm thinking of trying another SWG in case maybe it just isn't outputting what it should. As you say, I can't slam at this point so I'm running out of options.

 

[hawkmoon7]

Why did you raise the CYA to 90+? The app says that’s the top of the tolerable range, but ideally is 70-80. The FC level needs to be maintained always above 5ppm, never ever less. That’s why your target should be 14ppm. If you lose 4ppm due to normal daily use, the day ends with 11ppm which is decently above 5ppm.

If you are only raising it to 7ppm, losing 4 in a day easily brings you under the minimum which is why you may be growing algae. Did complete the SLAM with all three passing criteria? How did you do it with that level CYA?

I completed many SLAMs when my CYA was much lower. Out of desperation I raised CYA to highest (90 but overshot slightly) to try to keep the chlorine in. Last SLAM was completed about two and a half weeks ago when CYA was around 50. CC were always .5 or less. Overnight chlorine loss negligible. Held it at SLAM level for 3 days and then let it drift down took a bit over 2 weeks for it to fall to 2ppm, and that's with 14 hours a day of 100 SWG.

I like your idea of keeping it high, and then topping off at night. I think that's a good step I can take. I've been taking it to target and letting it dip below ideal before adding more. I can realistically take it to 12. If it doesn't fall below 7 by night. Then I'll top off to 12 again. Let's see how long I can keep that going since I can't SLAM any more.

 

[Orion7319]

I completed many SLAMs when my CYA was much lower. Out of desperation I raised CYA to highest (90 but overshot slightly) to try to keep the chlorine in. Last SLAM was completed about two and a half weeks ago when CYA was around 50. CC were always .5 or less. Overnight chlorine loss negligible. Held it at SLAM level for 3 days and then let it drift down took a bit over 2 weeks for it to fall to 2ppm, and that's with 14 hours a day of 100 SWG.

I like your idea of keeping it high, and then topping off at night. I think that's a good step I can take. I've been taking it to target and letting it dip below ideal before adding more. I can realistically take it to 12. If it doesn't fall below 7 by night. Then I'll top off to 12 again. Let's see how long I can keep that going since I can't SLAM any more.

Before you replace the SWG, I would try turning it off first and treat it as a regular chlorine pool for a while. You need to lower your CYA first though. It’s either organics or your SWG. I would hate for you to buy a new one only to come to find out it’s fine.

 

[hawkmoon7]

Before you replace the SWG, I would try turning it off first and treat it as a regular chlorine pool for a while. You need to lower your CYA first though. It’s either organics or your SWG. I would hate for you to buy a new one only to come to find out it’s fine.

Yeah, it's only a year old... But I'm going to try to see if a neighbor would let me "borrow" theirs for a few days as a test before trying to make a case to Pentair about it's effectiveness. I only recently raised CYA as a last resort to see if it'll help keep the chlorine in check. It's been a failure so far. My rationale was we are entering the rainy season, and in a few weeks, I'll be dumping inches of water nearly every week. So now's the time to see if high CYA did anything before I have to start draining water.

I do think I've identified at least one problem... that I'm letting chlorine bounce between target and too low. I am going to keep it higher than target with supplemental shock so it never dips below target. Pool has always been clear, CC's always near or at zero, PH mostly good but can rise fast with SWG at 100, I've lost track of how many SLAMs I did. If it weren't for the 8 or so gallons of shock every month, you'd think it was perfect!

The other thing I'm going to do is test chlorine at night and then in the morning WITH the SWG running all night. I've done the test and never drop more than about .5 at night with SWG off. But at 100%, I should notice some INCREASE in chlorine over night, right?

 

[Bperry]

Yeah, it's only a year old... But I'm going to try to see if a neighbor would let me "borrow" theirs for a few days as a test before trying to make a case to Pentair about it's effectiveness. I only recently raised CYA as a last resort to see if it'll help keep the chlorine in check. It's been a failure so far. My rationale was we are entering the rainy season, and in a few weeks, I'll be dumping inches of water nearly every week. So now's the time to see if high CYA did anything before I have to start draining water.

I do think I've identified at least one problem... that I'm letting chlorine bounce between target and too low. I am going to keep it higher than target with supplemental shock so it never dips below target. Pool has always been clear, CC's always near or at zero, PH mostly good but can rise fast with SWG at 100, I've lost track of how many SLAMs I did. If it weren't for the 8 or so gallons of shock every month, you'd think it was perfect!

The other thing I'm going to do is test chlorine at night and then in the morning WITH the SWG running all night. I've done the test and never drop more than about .5 at night with SWG off. But at 100%, I should notice some INCREASE in chlorine over night, right?

Try getting the FC back up to 14 and see if it stays there with the SWG going as-is.

 

[hawkmoon7]

Try getting the FC back up to 14 and see if it stays there with the SWG going as-is.

Will do.

By the way... could my proximity to a pond (about 25 feet away) cause algea problems? Again, I haven't seen it affect the water, but maybe it is putting a strain on the chlorine demand?

 

[Mdragger88]

If u are truly passing the oclt at target fc levels w/ fas/dpd test then u have eliminated organics as the cause for failure to maintain fc.
To test your swg you basically do a reverse oclt- an overnight chlorine gain test if u will. Test fc soon after dark - turn on swg @100 % & let it run all night long, test again at/before dawn. In 8hrs your cell should produce roughly 3ppm. Faulty cells can happen. Until u get things w/ the swg sorted use the manually chlorinated side of the FC/CYA Levels staying in target range at all times.

 

[hawkmoon7]

If u are truly passing the oclt at target fc levels w/ fas/dpd test then u have eliminated organics as the cause for failure to maintain fc.
To test your swg you basically do a reverse oclt- an overnight chlorine gain test if u will. Test fc soon after dark - turn on swg @100 % & let it run all night long, test again at/before dawn. In 8hrs your cell should produce roughly 3ppm. Faulty cells can happen. Until u get things w/ the swg sorted use the manually chlorinated side of the FC/CYA Levels staying in target range at all times.

Thanks. I will try that tonight.

 

[hawkmoon7]

Results of the test...

SWG set at 100, running all night. Fc was at 10. Cc tested between 0 and .5.
9 hours later, Fc just tested at 10, Cc tested between 0 and .5.

All the lights are on and green at the SWG, and bubbles are coming out of the return indicating hydrogen gas. I'm going to raise the Fc to 12 this morning so it doesn't drop below 7 today. Then tonight, I'll do another test without the SWG on and see if Fc reduces overnight... just to confirm that it is the SWG. Weird, because it really seems to be working.

 

[Mdragger88]

Results of the test...

SWG set at 100, running all night. Fc was at 10. Cc tested between 0 and .5.
9 hours later, Fc just tested at 10, Cc tested between 0 and .5.

All the lights are on and green at the SWG, and bubbles are coming out of the return indicating hydrogen gas. I'm going to raise the Fc to 12 this morning so it doesn't drop below 7 today. Then tonight, I'll do another test without the SWG on and see if Fc reduces overnight... just to confirm that it is the SWG. Weird, because it really seems to be working.

Have u checked it for scale? - You may have mentioned this previously.
If it is dead hopefully they will replace it.

 

[hawkmoon7]

Have u checked it for scale? - You may have mentioned this previously.
If it is dead hopefully they will replace it.

Just checked. It seems clean. I'm going to do an overnight test tonight without the SWG on, to see if I'm losing any chlorine without it. It's so odd, because it does look like it's working.

I also came up with an idea to maybe measure its actual output if it is underperforming. Here's my thought... according to the SWG calculator, if I switch to SPA mode only, and leave the SWG at 100% for an hour, I should see a rise of 7 Fc. That should be obviously detectable. To eliminate all variables, I'll do it after sunset. I'll then compare the Fc level after the one hour to the pool water. My thinking is this should take into account any Fc loss from algea during that hour. The difference between the SPA with SWG @ 100 for one hour and the Fc in the pool water without the SWG should equal the total output of the SWG (which is supposed to be 7).

Let me know if I'm missing anything.

 

[Mdragger88]

Sounds like a plan

 

[duraleigh]

I'm going to do an overnight test tonight without the SWG on

Just for clarification to every one, it can't be done any other way.

Adding chlorine to the pool after you take the first test for the OCLT by ANY means negates the validity of the OCLT