Need help understanding chlorine levels for SLAM.

[bobby2175]

My wife has been managing a slam on the pool and hot tub. She knows what she's doing with testing and adding chlorine.

Over the past few days, she's been testing chlorine multiple times a day and adding as needed, but we've been having trouble getting through the slam.

Over the past 24 hours, she's had to add a lot of chlorine to stay above slam levels in the spa. But when I got home tonight and did the test (multiple times including with reagents that I just bought), the FC is above 80! She had no reading even close to this. We were even able to confirm though our cameras the rough amount of the last chlorine added and there shouldn't be this big of a spike (from 20 to the 80+ I measured).

The slam on the pool is consistent between my measures and hers and is progressing as planned. It's only the spa that's an issue.

We did have 5 kids in the spa for a few hours on Thursday evening.

Is there such a thing as chlorine being locked up somehow and then all of a sudden showing up? Is it possible to get a high reading based on any other factors?

The chlorine was just purchased from the local pool shop and is the refillable liquid type.

What should be my next course of action? Should I be draining and refilling to lower FC quickly? Are there any other things that could go wrong?

I've been managing the pool over the past couple of years and very comfortable with testing and adding chemicals.

 

[PoolStored]

I don't think that your 80+ test is accurate, given the amounts of chlorine that has been added in your pool math logs.
I think you might just have testing error.
Let's start here.
Clean your vial with rubbing alcohol and dry thoroughly.
Use a 5mL sample of pool water. Each drop is 1FC.
1 heaping spoon of the 0870.
Wipe the tip of the 0871 with a wet paper towel.
Hold the bottle vertical.
SLOOOOWLY squeeze the bottle, allowing the drops to form and drop under their own weight.
Go slow and swirl.
Repeat until the sample clears.

Wipe the bottle once before you start. Try going slow with the drops, allowing them to drop under their own weight, swirl before the next drop.

Try that and report back.

 

[HermanTX]

The slam on the pool is consistent between my measures and hers and is progressing as planned. It's only the spa that's an issue.

We did have 5 kids in the spa for a few hours on Thursday evening.

Is the spa and pool connected?
It may be someone added chlorine directly to the spa and then you tested only the spa water. Since that is a much smaller body of water, the FC in that may have spiked high before being mixed with the pool.
It is always best to add chlorine directly to the pool and also test the pool. The spa will get the mixed water during circulation or spillover of the spa to the pool.

If you need to add chlorine directly to the spa, then do a very small quantity of it.

 

[bobby2175]

I don't think that your 80+ test is accurate, given the amounts of chlorine that has been added in your pool math logs.
I think you might just have testing error.
Let's start here.
Clean your vial with rubbing alcohol and dry thoroughly.
Use a 5mL sample of pool water. Each drop is 1FC.
1 heaping spoon of the 0870.
Wipe the tip of the 0871 with a wet paper towel.
Hold the bottle vertical.
SLOOOOWLY squeeze the bottle, allowing the drops to form and drop under their own weight.
Go slow and swirl.
Repeat until the sample clears.

Wipe the bottle once before you start. Try going slow with the drops, allowing them to drop under their own weight, swirl before the next drop.

Try that and report back.

Thanks for the great advice!

Cleaned everything up and redid the test based on your instructions and got to 41 drops = 41 FC.

Seems much more reasonable although a little bit high but not out of the realm of possibility with the added chlorine.

What did I do wrong with the test and how can I get more consistent with it? My setup is the TF Pro plus the MS40 stirrer. Perhaps it's to slow down on the drops and be more deliberate? Anything else to make this better?

What impact does heaping spoon vs level spoon of R-0870 have?

Thanks so much!

 

[PoolStored]

What did I do wrong with the test and how can I get more consistent with it? My setup is the TF Pro plus the MS40 stirrer. Perhaps it's to slow down on the drops and be more deliberate? Anything else to make this better?

Slowing down and allowing the drops to form drop under their own weight is one of the more common errors.
Slowing down and letting the chemical reaction happen while stirring is another.
Keeping your vial and pill clean is another.
Holding the reagent vertical is another.

Water Testing Errors - Further Reading

www.troublefreepool.com

 

[bobby2175]

Is the spa and pool connected?
It may be someone added chlorine directly to the spa and then you tested only the spa water. Since that is a much smaller body of water, the FC in that may have spiked high before being mixed with the pool.
It is always best to add chlorine directly to the pool and also test the pool. The spa will get the mixed water during circulation or spillover of the spa to the pool.

If you need to add chlorine directly to the spa, then do a very small quantity of it.

The two are not connected. Right now, I have the pump running 24X7 trying to successfully exit SLAM.

I checked the spa about 5 hours after the last chlorine addition.

 

[Bperry]

Thanks for the great advice!

Cleaned everything up and redid the test based on your instructions and got to 41 drops = 41 FC.

Seems much more reasonable although a little bit high but not out of the realm of possibility with the added chlorine.

What did I do wrong with the test and how can I get more consistent with it? My setup is the TF Pro plus the MS40 stirrer. Perhaps it's to slow down on the drops and be more deliberate? Anything else to make this better?

What impact does heaping spoon vs level spoon of R-0870 have?

Thanks so much!

Also a note…the goal of the slam is not to stay ABOVE slam level. It’s to increase UP TO slam level and bring it back up often. You are using a lot of chlorine and can dial it back quite a bit so you don’t waste so much.

And you should not be testing and adjusting pH during the SLAM. The pH tests are not accurate when FC is above 10ppm (using the Taylor pH test)

 

[HermanTX]

The two are not connected. Right now, I have the pump running 24X7 trying to successfully exit SLAM.

I checked the spa about 5 hours after the last chlorine addition.

Help us by explaining your set up. You have a separate spa not connected to the pool. Do you have algae in the spa? Is there a separate pump, filter for the spa?

Are you only focused on the pool to do the SLAM? It would be best to get that done and over. So test often and maintain FC at SLAM level for the given CYA level of the pool water. There is no reason to exceed SLAM FC value but to maintain it by testing every 4-6 hrs and bring the FC level back up to SLAM level.

 

[bobby2175]

Help us by explaining your set up. You have a separate spa not connected to the pool. Do you have algae in the spa? Is there a separate pump, filter for the spa?

Are you only focused on the pool to do the SLAM? It would be best to get that done and over. So test often and maintain FC at SLAM level for the given CYA level of the pool water. There is no reason to exceed SLAM FC value but to maintain it by testing every 4-6 hrs and bring the FC level back up to SLAM level.

I'm still having issues.

Yes, it is a separate spa not connected to the pool, separate pump, separate filter.

Had to slam the pool, but have been successfully out of it now for maybe 5-6 days and it's doing well.

The spa has always been completely clear and no algae present, but I cannot go overnight and maintain chlorine in the spa.

I've had to do slams the last couple of years upon opening the pool and spa and am generally able to get through them quickly. I'm generally pretty good with the testing and have done so the last couple of years without any issues. It's just not working this time.

I added extra chlorine to be able to get through the night and maintain slam levels - should have taken the CL to around 32.

When I tested it after an hour after adding the chlorine, it once again tests over 60 twice (once using 10 ml water and once with 5 ml of water), slow drops, vertical bottle...I just stopped putting more drops in but in either case, it didn't go clear.

I'm completely lost.

I think one thing I'll do is not do large chlorine doses and just maintain the slam level as best I can like you all have mentioned. It's all I can think of, but I've not run into this before and have been doing it this way the last couple of years (not saying it's right).

 

[bobby2175]

Also a note…the goal of the slam is not to stay ABOVE slam level. It’s to increase UP TO slam level and bring it back up often. You are using a lot of chlorine and can dial it back quite a bit so you don’t waste so much.

And you should not be testing and adjusting pH during the SLAM. The pH tests are not accurate when FC is above 10ppm (using the Taylor pH test)

I knew about the pH. I had tested before I went out of town but ran out of time to adjust it, so I knew I had to it when I got back. I didn't want my wife having to worry about messing with the acid.

 

[HermanTX]

Had to slam the pool, but have been successfully out of it now for maybe 5-6 days and it's doing well.

OK. So pool is clear. Your PM logs refer only to the pool. I see that FC is hovering around 26ppm . Are you letting this draw down over the next couple of days? What is your CYA for the pool water? I see about 3 weeks ago it was 50ppm CYA. Have you done a
Overnight Chlorine Loss Test to confirm you are done with the SLAM?

I added extra chlorine to be able to get through the night and maintain slam levels - should have taken the CL to around 32.

When I tested it after an hour after adding the chlorine, it once again tests over 60 twice (once using 10 ml water and once with 5 ml of water), slow drops, vertical bottle...I just stopped putting more drops in but in either case, it didn't go clear.

I'm completely lost.

This all relates tot he SPA - correct? What is volume of spa? What is the CYA of spa water? There are no logs or info related to the spa other than you state the FC is super high. If you are not holding FC then you may have algae that is not visible. do you have a ladder in the spa? A photo will help.
Try not to exceed SLAM level of FC for the SPA as it is a waste of chlorine. High levels of FC tend to decline quicker.
Can you post a full set of data for the spa water? Mainly want to know FC, CYA and if FC is under 10ppm then test for pH as well.

 

[bobby2175]

OK. So pool is clear. Your PM logs refer only to the pool. I see that FC is hovering around 26ppm . Are you letting this draw down over the next couple of days? What is your CYA for the pool water? I see about 3 weeks ago it was 50ppm CYA. Have you done a
Overnight Chlorine Loss Test to confirm you are done with the SLAM?


This all relates tot he SPA - correct? What is volume of spa? What is the CYA of spa water? There are no logs or info related to the spa other than you state the FC is super high. If you are not holding FC then you may have algae that is not visible. do you have a ladder in the spa? A photo will help.
Try not to exceed SLAM level of FC for the SPA as it is a waste of chlorine. High levels of FC tend to decline quicker.
Can you post a full set of data for the spa water? Mainly want to know FC, CYA and if FC is under 10ppm then test for pH as well.

Not sure why spa doesn't show up in my logs as I'm using pool math to track both the pool and spa.

For pool, yes, was able to get through all 3 stages of exiting slam. But I'm starting to question the FC level there as it is not going down at all in 4 days. It hasn't gotten fully warm yet, but will know more in the next few days as things warm up and we get more sun.

All issues I believe are only with the spa although I'm questioning pool FC.

Here are my spa stats:

Volume - 2500 gallons
No ladder
FC: 51 (used 5ml of water with each drop being 1 ppm)
CC: 0
pH: ? (due to slam)
Alk: 50
CYA: 30
Ca: 200 (but have added calcium and need to recheck)

Pics attached.

Thanks for all of the help!

 

[mknauss]

The FC level is way too high. Let the FC level return to SLAM level and retest OCLT>

 

[bobby2175]

The FC level is way too high. Let the FC level return to SLAM level and retest OCLT>

That's just it. I keep overshooting the FC by alot and I don't know how. I'm using effects of adding and it's just not working how it did last year. Trying to figure out what I'm doing wrong.

For example, I measured FC at 14, added 47 Oz of chlorine to take the FC into the low 30s (I know that's too high). But when I tested an hour later, it measured over 60 FC when I stopped adding drops. Cannot explain what I'm doing wrong as this all worked perfectly the last couple of years.

 

[Bperry]

That's just it. I keep overshooting the FC by alot and I don't know how. I'm using effects of adding and it's just not working how it did last year. Trying to figure out what I'm doing wrong.

If you are overshooting then the chlorine percentage is too low or your pool volume is too big.

 

[bobby2175]

If you are overshooting then the chlorine percentage is too low or your pool volume is too big.

I have the right % in pool math and successfully used the same volume last year which was confirmed by the pool builder.

Is it possible that the chlorine source % is incorrect? I'm using a refillable/returnable container from the local pool shop. Any way to test that?

 

[Bperry]

I have the right % in and successfully used the same volume last year.

Is it possible that the chlorine source % is incorrect? Any way to test that?

I suppose you could be testing incorrectly as well. It would be virtually impossible for the chlorine percentage to be any higher than it stated there’s ways to test it. It’s almost a certainty that it’s what it says it is or slightly less.

You aren’t using the 25 mL water sample by mistake are you?

 

[Parac]

I know you said it worked last year, but are you sure your volume is correct? 2500 gallons seems high for that spa pictured.
A square is easy to verify volume. What are the dimensions:
Height, water level to seat -
Height, Seat to floor -
Length and Width of upper sides -
Length and with of lower sides -

 

[bobby2175]

I suppose you could be testing incorrectly as well. It would be virtually impossible for the chlorine percentage to be any higher than it stated there’s ways to test it. It’s almost a certainty that it’s what it says it is or slightly less.

You aren’t using the 25 mL water sample by mistake are you?

Yes, I'm sure. I've done the test with 5 ml and 10 ml. I'm definitely questioning everything I'm doing, because nothing makes sense. I've also used 2 different reagent sets.

Here's a pic of what I put into pool math. I was expecting it to go up by 19, and somehow got over 50+. Anything you see wrong?

I double check the amount I pour twice - unfortunately I'm an engineer.

It all leads me back to the volume or the chlorine. Sounds like chlorine is unlikely an issue. I have not confirmed the volume of the spa myself - this was provided by the builder and I've used this for the past couple of years without any issues.

Im thinking I'm going to just let the chlorine drop and reassess.

 

[PoolStored]

How old are your reagents and where are they stored? Bad reagents will give high results.