The SLAM is over, and it's time to transition.

[nabril15]

That water looks like glass. Very nice. So why the excessive FC drop overnight? You lost 3 ppm of FC last night. That is THE question.

Thanks Pat. I like how you think. As an IT Project Manager, I have to look for the root of a problem and often break things down like you did. The answers below:
Reagents are stored in a kitchen cabinet.
How old are your reagents? The DPD powder is from January 2019 expiring 6/23 almost used up. I just received a new one and used it to test the same sample, and FC was 18.5. The 0871 liquid is from August 2019.
Do you use a speedstir to mix the solution? No sir. I stir after 2 drops as the color gets closer, 1 drop/stir/1drop/stir. I've been looking at getting a speedstir, yes, but spending the $30 is tough, I have to admit.

If there is nothing odd with the testing process, we have to focus our efforts back to the pool and equipment. So I'll ask to confirm the following:
- When was the last time you rinsed-off the cartridges? I put in a new one on March 23rd and only have one.
- Was the water circulating (low is fine) 24/7 and during the OCLT? No. I have a single-speed pump. But I did not leave it on last night in particular.
- When was the last time you popped-off that drain cover? Never. I do make it a point to circulate water through that drain 2 or 3 times a week. Twice a week, I also circulate water through the spa jets with the air blower turned on.
- Have you checked under the skimmer lid for anything odd? Behind the weir door perhaps? Yes, and they look clean
Just looking for any clues now.

 

[Texas Splash]

So your replies give us a couple things to consider:
- You said (unless that was a typo) "But I did not leave it on last night in particular." The pump should be running for the OCLT. Keeping the FC mixed well in the water is crucial. If the OCLT was not part of an ongoing SLAM (pump on 24/7) and only used for diagnostic purposes, then at the very least ensure the pump mixes water well for at least 30 minutes before grabbing the final evening water sample for testing, then let any new chlorine mix for about 20-30 minutes. Let the pump run about 30 minutes in the morning before the test sample is obtained.

- That drain cover could be an issue. At some point it would be good to go down there and inspect the underside of it. We've seen growth under the lids before.

 

[nabril15]

If the OCLT was not part of an ongoing SLAM (pump on 24/7) and only used for diagnostic purposes, then at the very least ensure the pump mixes water well for at least 30 minutes before grabbing the final evening water sample for testing, then let any new chlorine mix for about 20-30 minutes. Let the pump run about 30 minutes in the morning before the test sample is obtained.
- That drain cover could be an issue. At some point it would be good to go down there and inspect the underside of it. We've seen growth under the lids before.

Those are valid points Pat. Thanks again.
The pump was on 24/7 during the SLAM, but once done, I've always let it return to its normal 11:30am-7pm cycle. I've been looking at a variable-speed pump during the recent boredom, but I will have to wait until this motor quits before making that purchase. A voice in my head says, however, that I'm sure that it would be good for the overall pool chemistry to be able to leave it running overnight at a low setting...

For my night and morning samples, I've typically just grabbed from water that has been standing still. But I shall take note of your comments above to have water moving BEFORE the samples are taken. And during our next swim/splash/Pool-Rum-Fest, I will remove the cover.

Since we're being cerebral and have time....the pool builder only gave this 30ft long pool TWO return lines at opposite corners. I have them both pointed up towards the surface so as to direct leaves towards the skimmer. Should they be pointing down or straight so as to move water better? In the deep end, I don't picture too much water moving or only when the vacuum moves through.

 

[Texas Splash]

I have them both pointed up towards the surface so as to direct leaves towards the skimmer. Should they be pointing down or straight so as to move water better?

Yeah, two returns at opposite ends does't really do a whole lot for you, but you do the best you can with what you have. I think just pointing somewhat close to the surface without breaking through and causing aeration, might be best to try and help keep surface debris moving.

 

[nabril15]

@Texas Splash. After her mini swim practice, I had my daughter remove the main drain cover. From the surface it looks like horrible algae, but she swore that the colored stuff we see in the picture is yellowish, hard, and stuck to the walls and floor of the hole; perhaps it's accumulated diamondbrite from the resurface 3 years ago.
I took a sample after plenty of motion and it was 16. Let's see what it will read tomorrow morning after having moved the water for 30 minutes. Should the pump remain on overnight? And will that need to become a normal ritual?

 

[Texas Splash]

You can leave the pump off overnight if you wish. Just make sure to turn it back on at least 30 minutes before grabbing your water sample in the morning.

 

[nabril15]

You can leave the pump off overnight if you wish. Just make sure to turn it back on at least 30 minutes before grabbing your water sample in the morning.

Good morning
Last night, fc was 16, and this morning it was 14.
Perhaps the filter is the culprit??

 

[Texas Splash]

Well, at least you only lost 2 versus 3 like before. I think you said the cartridge was new, but it would be a good idea to give it a good rinse. I know in my single cart filter, the PSI doesn't really go very high to show when it's dirty, so it can be a bit misleading. Getting closer!

 

[nabril15]

@Texas Splash
Good morning Pat. Do you have big plans for the weekend? Who does???
The fc went to bed at 15.5 and woke up to 13, with CYA at 60, CH at 425 and TA at 70.

I will rinse that filter in a few hours, that's my big plan for the weekend, and I hope that is it. I don't lift any algae when brushing, and the water remains crystalline.

 

[Texas Splash]

The FC floss is getting less. and that's good. But I noticed one important thing. If your CYA is 60, your FC SLAM level is 24. See the FC/CYA Levels. So you really should increase the FC to 24 and maintain that for optimal SLAM results. Enjoy your weekend.

 

[nabril15]

The FC floss is getting less. and that's good. But I noticed one important thing. If your CYA is 60, your FC SLAM level is 24. See the FC/CYA Levels. So you really should increase the FC to 24 and maintain that for optimal SLAM results. Enjoy your weekend.

Yes sir, but technically, I'm done with the SLAM. That's when I opened this thread asking how to return to normal from a SLAM. So a week ago, I completed a slam with FC at 24, OCLT=0 and crystal water. Now, we're trying to solve the mystery of why FC is dropping so much DESPITE having passed a successful SLAM.

 

[Texas Splash]

That's right. I'm losing it. Well, it's great to see the FC loss getting less overnight and very close to passing. Hopefully your 24 FC loss isn't more than 4 ppm either. Your situation has been unique for sure. I'll be curious to see how your OCLT goes tomorrow.

 

[nabril15]

That's right. I'm losing it. Well, it's great to see the FC loss getting less overnight and very close to passing. Hopefully your 24 FC loss isn't more than 4 ppm either. Your situation has been unique for sure. I'll be curious to see how your OCLT goes tomorrow.

Good morning
The fc is at 10.5 this morning.
I pose a theoretical theory. My mahogany tree in the back has been shedding leaves like crazy, I'm talking about 4 or 5 daily FULL pole-baskets. There are a ton of leaves despite my constant efforts. Could that be affecting the overnight fc loss, since I obviously don't clean overnight??
The ph is 7.5, btw

 

[Texas Splash]

The fc is at 10.5 this morning

What was last night's beginning OCLT reading? The leaves? Well, if they are removed fairly quickly, I'm not sure how much of demand they place on chlorine. Perhaps a little. That is a lot of leaves though. Water still crystal??

 

[nabril15]

What was last night's beginning OCLT reading? The leaves? Well, if they are removed fairly quickly, I'm not sure how much of demand they place on chlorine. Perhaps a little. That is a lot of leaves though. Water still crystal??

It was 13.5 last night and the water remains deliciously clear. The filter cleaning is about to start.

 

[Texas Splash]

If you do another OCT this evening and the FC loss is the same, I'm inclined to believe there's a different explanation for the FC loss and not algae. You've SLAM'd for quite a while now with crystal water and no CCs. You inspected every accessible area to confirm nothing is growing under the drain cover, behind a light, etc. New cartridge and cleaned surfaces often. If you see something different, of course do what needs to be done, but I think you're about done.

 

[nabril15]

The filter was dirty but not substantially, and I didn't see any algae. I will keep at this, as all pool owners do.

Btw, is it possible to replace the plastic "nut" that tightens a pool pole? Is that piece sold by itself? Do you happen to know? They crack too easily.

Thanks a lot @Texas Splash. I really appreciate your help. Sometimes the obvious isn't quite so.

 

[Texas Splash]

is it possible to replace the plastic "nut" that tightens a pool pole? Is that piece sold by itself?

Ugh, I'm not sure. You might get lucky on Google, but my gut tells me it may be tough. Worth a few minutes of online browsing though. Have a great day.