OCLT

[jstblush]

Hi all,
Just want to make sure of something. I did an OCLT last night and this morning it tested at a loss of 1. Is that okay or does it have to be under one?
Thanks.
Sherry

 

[kcindc]

Per Pool School "If your FC level remained the same, or went down by 1.0 or less, the water is clean." Pool School - Perform the Overnight FC Loss Test (OCLT)

 

[Husky25]

1 or under. However, you could stay on the safe side and keep your FC up at SLAM levels today and do another test tonight.

 

[jstblush]

Thanks Karen.
Just wanted to make sure because I've seen a couple threads say to SLAM if it was 1 ppm loss. Been using lots of bleach so thought I would get it verified by someone.
Thanks again.
Sherry

- - - Updated - - -

Thanks Chris. Maybe I will try that today. It just seems like I've been using a lot of bleach. Maybe not, I don't know....

Sherry

 

[kcindc]

Would you mind posting up a full set of results? Just want to make sure you are in a good place.

 

[jstblush]

Here are my test results:
PH 7.9......maybe even 8
FC 5.5
CC 0
TC 5.5
TA 90
CH 75
CYA 40

Thank you
Sherry

 

[kcindc]

Those results look ok. Is the water crystal clear? Can you see the screw heads on the main drain cover?

Many folks use a lot more bleach this time of year because of the bright sun, high water temps and higher bathing loads. How much bleach are you adding every day?

 

[jstblush]

Crystal clear. Forgot to add PH, so edited last post. PH is 7.9, maybe even 8. I'm using anywhere between 3.5 to even 5 ppm per day. Usually more like 4 to 4.5 per day.
Here's what the water looks like now. Was thinking it was kind of high usage. Nothing different in bather load or anything else like that. Just a lot of hot (high 90's to 104) temps.
Sherry

https://www.flickr.com/photos/151173950@N02/shares/PoH1P9



Is my picture showing up for you? How about now?

 

[kcindc]

No, I can't see the photo. You are going through a lot. Do you have kids using the pool? "P" in the "ool" will really chew up a lot of FC.

You might bump your CYA up to 50 to see if that helps. Make sure you FC never gets to the minimum for your CYA level (link in my signature).

 

[Husky25]

Your pH needs to come down a scosche and if you are concerned about FC usage, you may consider bumping up your CYA. My pool has a bit more volume than yours and I use about a half gallon of 12.5% LC (on average)/day, just to give you an idea. It's pretty cool here now but we just experienced a heat wave and temps are going to 80 again by the end of the week.

 

[jstblush]

Thank you guys!
I am posting a picture so you can see how clear the water is. It's been like this all summer, but it just seems to be using more FC than it ever has. So I think I will start a SLAM either today or tomorrow. At least I will bring the FC up to SLAM level today and do an OCLT in the morning I was going to raise CYA to 50 and see if that helped, but definitely don't want to raise it before a SLAM. And it didn't seem to make much difference when I raised it from 30 to 40. That's why I was wondering if there is something lurking

So if I want to raise FC to SLAM level and check in the morning (OCLT) should I raise it right now or wait until this evening?
https://www.flickr.com/photos/151173950@N02/shares/PoH1P9

Thanks again,
Sherry

P.S. I think I will start a new thread and do a survey about FC usage in the hot, all day long in the sun pools and see what everyone else is experiencing.

 

[jstblush]

Oh, forgot. No, we don't have little ones to pee in the pool. The ones that swim in our pool are 11 years old and older and they get out and use the bathroom. LOL (at least I hope they do....haha)

Chris, I wish we were only using half a gallon! Ours is 10% bleach with fresh dates. And I've been checking after I add to see what I end up with. And I will definitely lower the PH. It kind of moves around in the 7.5-7.9 range.

Sherry

 

[kcindc]

Thank you guys!
I am posting a picture so you can see how clear the water is. It's been like this all summer, but it just seems to be using more FC than it ever has. So I think I will start a SLAM either today or tomorrow. At least I will bring the FC up to SLAM level today and do an OCLT in the morning I was going to raise CYA to 50 and see if that helped, but definitely don't want to raise it before a SLAM. And it didn't seem to make much difference when I raised it from 30 to 40. That's why I was wondering if there is something lurking

So if I want to raise FC to SLAM level and check in the morning (OCLT) should I raise it right now or wait until this evening?
https://www.flickr.com/photos/151173950@N02/shares/PoH1P9

Thanks again,
Sherry

P.S. I think I will start a new thread and do a survey about FC usage in the hot, all day long in the sun pools and see what everyone else is experiencing.

We all have very different conditions, weather, sun, bathing load, debris from trees, etc. For example, I have a very high daily FC demand. I get very minimum human usage, but I have a 95 lb lab who swims several times a day. He is constantly dropping his dirt crusted toys in the pool. He will even play fetch with himself in the pool.

You might be better off checking everywhere for any hidden algae like skimmer throats, skimmer weirs (the foam on the doors can harbor algae), behind lights, behind stairs.

Doing a brief SLAM might take care of any pending algae blooms. Just make sure you brush the pool after your raise your FC to SLAM levels. After your brief SLAM, I would increase your CYA by 10 to help protect your FC from the sun a little better.

 

[jstblush]

How do you check behind stairs that are permanently there? I'll make sure to check the other places. Thank you!
Sherry

BTW Could you see the picture the second time? I posted a link instead of the other way. Never had a problem posting directly from my pc before. Who knows.............

 

[jstblush]

How do you check behind stairs that are permanently there? I'll make sure to check the other places. Thank you!

Sherrry

 

[kcindc]

I could see the picture the second time. My apologies, but I should not have said for you to clean behind your stairs as that only applies to above ground pools.

Did you see any algae behind your lights or in the skimmers?

 

[Husky25]

It looks to me like you have passed the OCLT (<1 ppm FC loss overnight, .05 or less CC, and clear water).

According to PoolMath, a 121 jug of 10% concentrate should raise FC in a 19k gallon pool by 5ppm. So if you are losing 4ppm during the day, you are pretty much replacing what is broken down by the sun with one jug. If the water is not clear to your satisfaction, you can add a 1/4 cup of diatomaceous earth to the skimmer, which will help the sand filter a bit more. Just be aware that DE causes the pump pressure to rise rapidly if you add too much. This will cause you to have to backwash almost immediately, which defeats the original purpose.

 

[kcindc]

When performing an OCLT, it says to turn off your source of chlorine so that no new chlorine is added. Does this imply that I should be running my pump overnight while doing the test? I ask this because if I'm not actually running my pump then my liquidator won't be adding any chlorine to the pool, whether the needle valve is open or not.

It is best to start your own thread with your own question to keep from confusing the OP and other posters. I've asked a MOD to split your question into a new thread.

If you are performing an OCLT, you should turn off the liquidator. Not sure if you have a separate valve to shut it off, but it would be best. Remember that your water needs to be circulating for 30 minutes prior to any testing to ensure an accurate result. As such, your liquidator will be adding chlorine if you don't shut it off and that could mess with the results.