What is consuming chlorine?!? SWCG can't keep up. Been SLAMing. Crystal clear pool now. Never algae on walls .

[TaylorN]

The powder amount doesn’t affect the test as long as there’s a few undissolved particles in there it’s fine. Note that heat also degrades chlorine, not just UV.

Wow! what a revelation!

I just tested the water with 1, 2, and 3 perfect scoops of the R-0870 DPD powder (shaken for 30 seconds) and 10mL of pool water each, and they all cleared out at exactly 24 drops of R-0871 FAS-DPD Titrating reagent.

Dang, here I was trying to be exact because I figured it was a chemistry reaction that was balanced ratios. But I guess the powder binds with chlorine and any excess un-bound powder is no longer a part of the reaction with the drops. So the 2 scoop recommendation should always fulfill the minimum required powder, especially for a 10mL sample... and not crazy levels of chlorine. Out of sheer curiosity, I wonder what the maximum chlorine amount 2 scoops will accurately read up to?

 

[TaylorN]

UPDATE:
--------------------------------------
On Friday (9/15) the pool was reading 13.5ppm fC at 8am. The SWCG was set to 0%. Then I went out of town.
This morning (9/18) the pool was reading 12ppm at 8:30am.

So it looks like we should be in the clear. Dropping only ~1.5ppm fC over the course of 3 full (cloudy) days with the cover closed sounds like a win.

My plan of attack is to set the SWCG to 100% today and then test the pool after its scheduled 8 hour pump run (still cloudy with cover closed) to see how much the SWCG was able to produce in 8 hours, and mark that for future reference.

After today I am going to set the SWCG back to 0% and leave the cover open for the rest of the week. We have a pool party scheduled Saturday afternoon for my daughters bday. So in order to have "safe" levels of chlorine, I will bring the CYA up from 35ppm to 80ppm on Friday and will make sure the fC is between 7-10ppm when the CYA is added. But I guess even if the fC was still at 12ppm by then, and we didn't add any CYA (still at 35ppm), the pool would still be "safe"

Thanks all!

 

[Bperry]

Wow! what a revelation!

I just tested the water with 1, 2, and 3 perfect scoops of the R-0870 DPD powder (shaken for 30 seconds) and 10mL of pool water each, and they all cleared out at exactly 24 drops of R-0871 FAS-DPD Titrating reagent.

Dang, here I was trying to be exact because I figured it was a chemistry reaction that was balanced ratios. But I guess the powder binds with chlorine and any excess un-bound powder is no longer a part of the reaction with the drops. So the 2 scoop recommendation should always fulfill the minimum required powder, especially for a 10mL sample... and not crazy levels of chlorine. Out of sheer curiosity, I wonder what the maximum chlorine amount 2 scoops will accurately read up to?

Generally TFP recommends one heaping scoop of powder when using a 10ml sample. It’s plenty and saves a touch of powder over time.

 

[Newdude]

+1. Make a snowball on the spoon and it's good.

 

[TaylorN]

Generally TFP recommends one heaping scoop of powder when using a 10ml sample. It’s plenty and saves a touch of powder over time.

+1. Make a snowball on the spoon and it's good.

Awesome! I didn't know that!

What is the recommended scoop procedure for 25mL sample?

 

[Newdude]

What is the recommended scoop procedure for 25mL sample?

I would do 2 snowballs, but there's simply no need for the 25ml accuracy. A 2.4 and 2.5 equally suck for all CYA values and a 8.6 and 9.0 are equally as great for (most) CYA values.

If I was to pass an OCLT by .2, I wouldn't be happy with 'Cs get degrees'. I want to pass my OCLT with flying colors seen by either sample size.

 

[TaylorN]

I would do 2 snowballs, but there's simply no need for the 25ml accuracy. A 2.4 and 2.5 equally suck for all CYA values and a 8.6 and 9.0 are equally as great for (most) CYA values.

If I was to pass an OCLT by .2, I wouldn't be happy with 'Cs get degrees'. I want to pass my OCLT with flying colors seen by either sample size.

2 snowballs, check!

And I totally get your point about 25ml accuracy for daily measurements in maintenance mode. You are either good at plus or minus 8 or bad at plus or minus 2.

For OCLT, maybe 25mL accuracy is better though(?). its essentially either perfectly accurate to the drop, or ~0.4ppm less than what you are expecting, right? The last drop to clear it out may only need 0.1ppm of the formula to go from pink to clear, but we are counting the last drop, yeah? If that is a true statement (which I am not sure it is), then if we are shooting for below 1ppm OCLT, and I get a 1ppm reading with 10mL sample, can I trust that I am truly at 1ppm or am I really at 1.4ppm? Or am I really at 0.6ppm, but get a reading of 1ppm dropwise. 0.6ppm seems like a good passing number, but 1.4ppm seems like a solid failure

However, if I get a 0.5ppm with 25mL sample, I can be way more confident that I am closer to 0.5ppm than I am to 1ppm? Just over analyzing.... or thinking about it incorrectly...

Like I felt very good about essentially performing a 3 day duration OCLT and only dropping 1.5ppm (with 10mL sample) over those 3 days. At most I could be 1.9ppm lost over 3 days which is still about 0.6ppm per 24hours. So I am feeling pretty good/confident about that right now

 

[Newdude]

then if we are shooting for below 1ppm OCLT, and I get a 1ppm reading with 10mL sample, can I trust that I am truly at 1ppm or am I really at 1.4ppm? Or am I really at 0.6ppm, but get a reading of 1ppm dropwise. 0.6ppm seems like a good passing number, but 1.4ppm seems like a solid failure

1 FC loss overnight is an OCLT pass by the rulebook. But personally if I went through all the effort and expense, I'd hold for a day or 3 more to pass with .5 or 0 using the old trusty 10ml. The extra resolution of the 25ml sample would only help some of the time there, if the results lined up just so.

And for all other times it's completely not needed.

But. Your pool, your rules. You test however you wish per the standard recommendations. We can work with either potato or pahtahto and we're just thrilled you got spuds.

 

[TaylorN]

1 FC loss overnight is an OCLT pass by the rulebook. But personally if I went through all the effort and expense, I'd hold for a day or 3 more to pass with .5 or 0 using the old trusty 10ml. The extra resolution of the 25ml sample would only help some of the time there, if the results lined up just so.

And for all other times it's completely not needed.

But. Your pool, your rules. You test however you wish per the standard recommendations. We can work with either potato or pahtahto and we're just thrilled you got spuds.

hahahaha! that last part got me laughing out loud for sure.

so an OCLT of 0ppm is possible? I figured during summer with a warm pool there is always something breeding/multiplying/consuming-chlorine.

Lastly, I know TFP recommends higher CYA levels for SWCG pools, but I swear I have seen folks on the forums say if you have a covered pool, they can be treated as partially indoor pools (assuming the target gets maintained, which ours didn't), and coincidentally shoot for a CYA of 35. Of course that would lead to "easier" SLAMs and potentially more effective free chlorine considering the government write-ups on cryptosporidiosis(?). But then again I actually trust TFP more than the government

I am overthinking this again....so do we move towards CYA of 80 and target fC of 6-11 (leaning toward target of 10) or CYA of say 40 and a target fC of 3-7 (Leaning toward 6-7fC)? I actually like the concept of having CYA of 80, because the pool is supposedly safe to swim in with fC levels less than slam level of 31ppm(?!?!) Realistically if the fC got up to 15ppm at CYA 80, it sounds like there is no need for concern. It would be easier to maintain 7-15ppm fC at CYA 80, than it is to hit the smaller 3-7ppm window at 35 CYA, especially after large kid pool parties and 86 degree water, right?


Thanks!

 

[an1vrsy]

After today I am going to set the SWCG back to 0% and leave the cover open for the rest of the week. We have a pool party scheduled Saturday afternoon for my daughters bday. So in order to have "safe" levels of chlorine, I will bring the CYA up from 35ppm to 80ppm on Friday and will make sure the fC is between 7-10ppm when the CYA is added. But I guess even if the fC was still at 12ppm by then, and we didn't add any CYA (still at 35ppm), the pool would still be "safe"

I wouldn't go through all of that for your pool party this coming Saturday. I would not add that much CYA this late in the swim season. You mentioned you heat the pool. Leaving the cover open overnight, you will lose a lot of that heat and water loss because of evaporative cooling. The air temps are significantly lower than your pool water temp.

I would though lower the SWG percentage to 50%. You only run for 8 hours. During the day, open the cover. Close your pool cover when the sun is off the water. The sun may not have set but the pool is in the shade. So cover it. Check your FC levels tomorrow, see how far it has dropped. Do the same tomorrow depending upon how far FC has fallen. Again CYA values, round up. CYA 35 is CYA 40. Oh, btw, add a gallon of liquid chlorine after the pool party. That will raise the FC 4.3 ppm. Who knows how much the kids had drank during the party and wouldn't get out of the pool when necessary.

But. Your pool, your rules. You test however you wish per the standard recommendations.

+1

 

[Newdude]

so an OCLT of 0ppm is possible?

It is. I'd be just as happy with .5.

but I swear I have seen folks on the forums say if you have a covered pool, they can be treated as partially indoor pools

Absolutely. You don't have the day to day UV concern with the pool closed. But. Pay special mind for all day swims/parties as those aren't your usual game plan and would need a temporary shift in strategy to account for traditional UV loss during those times.

cryptosporidiosis(?)

Crypto is incredibly rare in residential pools. Like MegaBall rare.

It would be easier to maintain 7-15ppm fC at CYA 80, than it is to hit the smaller 3-7ppm window at 35 CYA, especially after large kid pool parties and 86 degree water, right?

Realistically how often does that happen. If every weekend or more, then yes. But if it's a handful of times a season, just dose high with LC before and verify you have plenty of leftovers after. The residuals may take a day to oxidize with that much sunblock and whatnot.

 

[PoolStored]

so an OCLT of 0ppm is possible?

Yes, but not necessary to pass OCLT.

I swear I have seen folks on the forums say if you have a covered pool, they can be treated as partially indoor pools (assuming the target gets maintained, which ours didn't)

Keep swearing, not likely. Indoor pools don't get UV, so they typically have UV or other system. Outdoor pools get UV, cover or not. Just less UV that uncovered pool. That just means the your daily FC demand will be lower, your pH rise will be lower, your evaporation will be lower and your heat loss will be lower (assuming solar cover).

I am overthinking this again....so do we move towards CYA of 80 and target fC of 6-11 (leaning toward target of 10) or CYA of say 40 and a target fC of 3-7 (Leaning toward 6-7fC)? I actually like the concept of having CYA of 80, because the pool is supposedly safe to swim in with fC levels less than slam level of 31ppm(?!?!)

Yes, you are overthinking. The only reason to run higher CYA is to lower FC demand...and extend cell life (SWCG) or reduce chlorine cost. No Other Reason. The ranges in the FC / CYA relationship are to maintain the same level of HOCl...the stuff that keeps the pool sanitized.

Realistically if the fC got up to 15ppm at CYA 80, it sounds like there is no need for concern.

True. Same it true if your CYA is 40 and you got FC up to 10.

It would be easier to maintain 7-15ppm fC at CYA 80, than it is to hit the smaller 3-7ppm window at 35 CYA, especially after large kid pool parties and 86 degree water, right?

Yes, you are overthinking. The only reason to run higher CYA is to lower FC demand. No Other Reason. The ranges in the FC / CYA relationship are to maintain the same level of HOCl...the stuff that keeps the pool sanitized (see chart above...) You have made the CYA 40 window smaller. You can run up to FC of 16 with 40 CYA and still be safe.

potentially more effective free chlorine considering the government write-ups on cryptosporidiosis(?).

See chart above...no more effective...same.

 

[TaylorN]

I wouldn't go through all of that for your pool party this coming Saturday. I would not add that much CYA this late in the swim season. You mentioned you heat the pool. Leaving the cover open overnight, you will lose a lot of that heat and water loss because of evaporative cooling. The air temps are significantly lower than your pool water temp.

I would though lower the SWG percentage to 50%. You only run for 8 hours. During the day, open the cover. Close your pool cover when the sun is off the water. The sun may not have set but the pool is in the shade. So cover it. Check your FC levels tomorrow, see how far it has dropped. Do the same tomorrow depending upon how far FC has fallen. Again CYA values, round up. CYA 35 is CYA 40. Oh, btw, add a gallon of liquid chlorine after the pool party. That will raise the FC 4.3 ppm. Who knows how much the kids had drank during the party and wouldn't get out of the pool when necessary.


+1

Thanks for the recommendation.

Not to complicate things, but I had turned down the temperature of the pool to alleviate high pool temp causing excessive algae growth, plus the past 4 days have been cloudy and drizzly, so without heating, the pool dropped to 76 degrees over the past couple weeks (during the SLAM).

With that being said, I took a measurement this morning at 9am which was 12ppm fC, then turned up the SWCG to 100% (from 0%) and let the pump continue running (as usual). I then took a measurement at 5pm (15mins ago) and the pool was 13.5ppm fC. So everything seems to be back to "normal". A few weeks ago when I would run the pump for 12 hours, it wouldn't gain any chlorine throughout the day at 100%. Now at 8 hrs it is able to gain 1.5ppm fC.

So I think I will do what you recommended and just leave the CYA low (35/40) and keep let the pool naturally reduce fC throughout the week with the pool cover open during the day, and close the cover at night. Hopefully targeting fC of 7 before the party on Saturday. and then based on the liquid urine ratio, add some liquid chlorine on sunday

 

[TaylorN]

It is. I'd be just as happy with .5.

Absolutely. You don't have the day to day UV concern with the pool closed. But. Pay special mind for all day swims/parties as those aren't your usual game plan and would need a temporary shift in strategy to account for traditional UV loss during those times.

Crypto is incredibly rare in residential pools. Like MegaBall rare.

Realistically how often does that happen. If every weekend or more, then yes. But if it's a handful of times a season, just dose high with LC before and verify you have plenty of leftovers after. The residuals may take a day to oxidize with that much sunblock and whatnot.

Cool Cool! that is good info! Thanks

 

[TaylorN]

Yes, but not necessary to pass OCLT.

Keep swearing, not likely. Indoor pools don't get UV, so they typically have UV or other system. Outdoor pools get UV, cover or not. Just less UV that uncovered pool. That just means the your daily FC demand will be lower, your pH rise will be lower, your evaporation will be lower and your heat loss will be lower (assuming solar cover).

Yes, you are overthinking. The only reason to run higher CYA is to lower FC demand...and extend cell life (SWCG) or reduce chlorine cost. No Other Reason. The ranges in the FC / CYA relationship are to maintain the same level of HOCl...the stuff that keeps the pool sanitized.

True. Same it true if your CYA is 40 and you got FC up to 10.

Yes, you are overthinking. The only reason to run higher CYA is to lower FC demand. No Other Reason. The ranges in the FC / CYA relationship are to maintain the same level of HOCl...the stuff that keeps the pool sanitized (see chart above...) You have made the CYA 40 window smaller. You can run up to FC of 16 with 40 CYA and still be safe.

See chart above...no more effective...same.

Excellent info.

Based on that chart it looks like with a CYA of 70, you'd need about 9ppm fC to be effective against Algae? And CYA of 30 would need about 3ppm FC to be effective against Algae? Is that how I am seeing it, or is that something else?

As for higher CYA = longer cell life (and lower FC demand), that only really applies to when the pool is uncovered and pool is exposed to the sun, correct? I get that we aren't avoiding 100% UV with cover on, but I'd guess it will be less than 5% (if not 1%) of what a noncovered pool would have have. So if the pool is not used and is covered for a 2 week stretch we shouldn't have very much FC demand. Then if we use the pool for a long afternoon/pool-party, the FC could drop from say some random example of 4ppm (at CYA=40) to 0 over the course of a couple days (initial sun degradation and then delayed oxidation). But if we had CYA of 70/80 and FC of 10 before a party, the FC would be protected when the cover is open from higher CYA and would only have delayed oxidation and might only drop to say a 7-8ppm or so, which is still higher than minimum recommendation, and wouldn't have to worry about dipping into the bad territory? I know those are arbitrary what-ifs....

So for our case, having a higher CYA wouldn't be that beneficial to extend cell life because we don't really need it to work super hard most of the time since the pool is covered 95%+ of the time. As long as we don't let the fC dip below the target for CYA 40, then we'd be golden. Just need to crank the SWCG to 100% for a day or two after a party or dump 0.5/1.0 gallon of chlorine in afterwards.

ultimately the goal is to never let the pool get below minimum target for too long. extending the cell via high CYA wouldn't be too applicable for us with a cover, right?

 

[Newdude]

ultimately the goal is to never let the pool get below minimum target for too long. extending the cell via high CYA wouldn't be too applicable for us with a cover, right?

Correct.

since the pool is covered 95%+ of the time. As long as we don't let the fC dip below the target for CYA 40, then we'd be golden.

Correct.

Just need to crank the SWCG to 100% for a day or two after a party or dump 0.5/1.0 gallon of chlorine in afterwards.

Many of us pre-treat and are covered before the inevitable party loss happens. Then we monitor afterwards to ensure we stay free and clear from minimum.

 

[Bperry]

Excellent info.

Based on that chart it looks like with a CYA of 70, you'd need about 9ppm fC to be effective against Algae? And CYA of 30 would need about 3ppm FC to be effective against Algae? Is that how I am seeing it, or is that something else?

As for higher CYA = longer cell life (and lower FC demand), that only really applies to when the pool is uncovered and pool is exposed to the sun, correct? I get that we aren't avoiding 100% UV with cover on, but I'd guess it will be less than 5% (if not 1%) of what a noncovered pool would have have. So if the pool is not used and is covered for a 2 week stretch we shouldn't have very much FC demand. Then if we use the pool for a long afternoon/pool-party, the FC could drop from say some random example of 4ppm (at CYA=40) to 0 over the course of a couple days (initial sun degradation and then delayed oxidation). But if we had CYA of 70/80 and FC of 10 before a party, the FC would be protected when the cover is open from higher CYA and would only have delayed oxidation and might only drop to say a 7-8ppm or so, which is still higher than minimum recommendation, and wouldn't have to worry about dipping into the bad territory? I know those are arbitrary what-ifs....

So for our case, having a higher CYA wouldn't be that beneficial to extend cell life because we don't really need it to work super hard most of the time since the pool is covered 95%+ of the time. As long as we don't let the fC dip below the target for CYA 40, then we'd be golden. Just need to crank the SWCG to 100% for a day or two after a party or dump 0.5/1.0 gallon of chlorine in afterwards.

ultimately the goal is to never let the pool get below minimum target for too long. extending the cell via high CYA wouldn't be too applicable for us with a cover, right?

Note that chlorine degrades in the sealed bottle and so heat and time also “consume” chlorine so don’t get too confident in the cover.

 

[wireform]

I tend to keep covered pools in the 50-60 range and FC accordingly in the higher side of target but that's just my rule so I never get into trouble when the FC slips more then usual for some foreseen reason which went uncalculated.

 

[PoolStored]

Based on that chart it looks like with a CYA of 70, you'd need about 9ppm fC to be effective against Algae? And CYA of 30 would need about 3ppm FC to be effective against Algae? Is that how I am seeing it, or is that something else?

The point of using the chart was to explain the relationship of FC and CYA levels and corresponding HOCl level.

Stop overthinking. Read this article and follow the recommendations of the tool on the page to maintain your FC...and never let your levels get to "minimum." Link-->FC/CYA Levels

As for higher CYA = longer cell life (and lower FC demand), that only really applies to when the pool is uncovered and pool is exposed to the sun, correct? I get that we aren't avoiding 100% UV with cover on, but I'd guess it will be less than 5% (if not 1%) of what a noncovered pool would have have. So if the pool is not used and is covered for a 2 week stretch we shouldn't have very much FC demand. Then if we use the pool for a long afternoon/pool-party, the FC could drop from say some random example of 4ppm (at CYA=40) to 0 over the course of a couple days (initial sun degradation and then delayed oxidation). But if we had CYA of 70/80 and FC of 10 before a party, the FC would be protected when the cover is open from higher CYA and would only have delayed oxidation and might only drop to say a 7-8ppm or so, which is still higher than minimum recommendation, and wouldn't have to worry about dipping into the bad territory? I know those are arbitrary what-ifs....

Again, you are overthinking it. It also depends on the type of cover. I have a solar cover. My FC demand when covered is about 50% of my covered demand. It is easier to not worry about how much the cover does or does not impact anything. Test daily, dial your pump time and % output to keep your FC in the "recommended" range...Atain, Link-->FC/CYA Levels

So for our case, having a higher CYA wouldn't be that beneficial to extend cell life because we don't really need it to work super hard most of the time since the pool is covered 95%+ of the time. As long as we don't let the fC dip below the target for CYA 40, then we'd be golden. Just need to crank the SWCG to 100% for a day or two after a party or dump 0.5/1.0 gallon of chlorine in afterwards.

I would say, leave it at 40 for a few weeks and get good at keeping your FC in Range. That will give you some sense of the amount you have to run your cell, and give you practice at maintaining FC. Then add 10ppm of CYA and see how much your FC demand changes. Then you will know.

Here is my routine, I run pump 24/7: April 5%, May 10%, June 15%, July 15%, Aug 10%, Sep/Oct 0-5%. When I take the cover off, I turn the SWCG up to 50% for the duration of the cover off, and back to baseline % when the cover goes back on. My FC is stable. You can even test DURING a party and add chlorine or up SWCG %...no need to wait to the end of the day, and likely no need to run for days.

ultimately the goal is to never let the pool get below minimum target for too long. extending the cell via high CYA wouldn't be too applicable for us with a cover, right?

You combined "minimum" with "target". I would substitute "EVER" for crossed off words above. Never ever let it get below "MINIMUM," better, never it let it get below MINIMUM + 1. Always keep it in "Target Range."


Last thought. It is better to keep your pool at the top of the recommended range as you learn your FC demand, covered, uncovered and "party mode." That way if you are surprised by a bigger demand day than you expected, you have more "skoosh" room before you hit minimum.

 

[TaylorN]

Correct.

Correct.

Many of us pre-treat and are covered before the inevitable party loss happens. Then we monitor afterwards to ensure we stay free and clear from minimum.

That sounds like a good idea. Thanks