Middle of Slam - First time testing FAS-DPD

AmyBarton

Member
Jun 3, 2017
17
OK
I am in the middle of a Slam. My water was green although I could not see algae growing nor was any picked up with the vacuum. First time doing a FAS-DPD testing. My CYA was high at 65 so I had to slam hard. Please let me know if my calculations are correct. 1. Filled to 25mL. 2. After adding R-0870 the sample did turn a dark pink (have pic if needed). 3. it took 82 drops to go to colorless. 4. 16.40 ppm free chlorine. 5. Turn a light pink. 6. R-0871 added 4 drops then turned pink = 0.80. 7. Multiply dorps in Step by equ. = 0.80?????? Is this correct? The Target FC around 8/10 and Slam should be 28 according to the slam chart. If this is the case I am still way under the slam? My water however is not green anymore. It is a cloudy white color so I know something is working. Help!
 

Texas Splash

Mod Squad
TFP Expert
LifeTime Supporter
Amy ... too much math. :hammer: ha. Do the FC test as folllows:
"Use a 10ml water sample and add ONE generous scoop of powder. Mix until clear while counting the drops. Divide the result in half and that's yoru FC."

Example - 40 drops equals an FC of 20.

You are correct in that we round-up your CYA to 70, so your SLAM FC level is 28. :)
 

AmyBarton

Member
Jun 3, 2017
17
OK
okay so I did that and my FC is 16. So to get to 28 I need to keep adding 10% chlorine? How much would you suggest? Just to get to this point I have added 15 gallons of 10% bleach ;-(
 
Last edited:

IceShadow

Gold Supporter
Jun 8, 2019
1,071
Milwaukee, WI
If you're SLAMMing, test at least three times a day or up to once an hour and add after each test to get back to 28. Brush and vacuum often. The more you do these things the quicker it will go :)
 

AmyBarton

Member
Jun 3, 2017
17
OK
Thank you everyone for your help. I added in 3 gallons and hope that will bring me up to 28. Will check in 2 hours. With all this chlorine, will it bring down my high CYA? Previously to learning about BBB, I used the chlorine tabs and realized that was raising my CYA so I stopped that.
 

Texas Splash

Mod Squad
TFP Expert
LifeTime Supporter
With all this chlorine, will it bring down my high CYA?
Unfortunately, no. Only a water exchange of some degree will begin to lower CYA. Your sand filter will help with that over time. But at 70 now, while on the high end, will get you through a hot summer. After the SLAM, just keep the FC balanced as seen on the FC/CYA Chart. Each month a little CYA should degrade, and then by next season it should be lower as long as you don't add anymore stabilizer or pucks.
 
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AmyBarton

Member
Jun 3, 2017
17
OK
When I started the slam process my cya was 65. So I was trying to get FC up to 28. Yesterday the highest I got was 16, added 3 gallons and tested 4 hours later and got 14. Last night I added 3 more gallons and this morning tested at 14. I have my pump on 24/7 all the time. I have backwashed and rinse many times and that is clear. I have my automatic pool cleaner sit in bleach to disinfect and then have ran that several times and it does really pick up anything. I have added 24 gallons of 10% in total through 2 days to reach the goal but can't get there. What to do? I have attached pictures. Today my water is crystal clear. I just tested my water. The temps here in Oklahoma have been in the high 90's. Thank you!
FAS-DPD 14
FC 2
PH 8.2
TA 130
CH 150
CYA 55
CC-0
 

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Last edited:

AmyBarton

Member
Jun 3, 2017
17
OK
When I started the slam process my cya was 65. So I was trying to get FC up to 28. Yesterday the highest I got was 16, added 3 gallons and tested 4 hours later and got 14. Last night I added 3 more gallons and this morning tested at 14. I have my pump on 24/7 all the time. I have backwashed and rinse many times and that is clear. I have my automatic pool cleaner sit in bleach to disinfect and then have ran that several times and it does really pick up anything. I have added 24 gallons of 10% in total through 2 days to reach the goal but can't get there. What to do? I have attached pictures. Today my water is crystal clear. I just tested my water. The temps here in Oklahoma have been in the high 90's. Thank you!
FAS-DPD 14
FC 2
PH 8.2
TA 130
CH 150
CYA 55
CC-0
 

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Texas Splash

Mod Squad
TFP Expert
LifeTime Supporter
So it looks like your new CYA is about 60, but you can't seem to get the FC to 24? That's odd. Usually we have very good success using the PoolMath tool to figure out how much bleach to add based on the gallon size of your pool. Two things to watch though ..... is the bleach fresh and was the percentage strength updated on the PoolMath tool. Once you add x-amount of bleach, give it about 20 minutes as re-test to see if you made it. If not, something is off. Maybe the pool size is larger than expected?

Your water definitely improved since yesterday. :goodjob: I will say that the FC will drop faster when at a SLAM level. I would continue with what you have been doing today and consider doing an Overnight Chlorine Loss Test tonight. I would be curious to know how much FC you lose overnight.

Not sure what you meant with your test above for FAS-DPD 14 then FC 2? Was the FC 2 from the OTO viewing glass? Regardless, you can simply use the FAS-DPD for FC testing. It's more accurate.
 

AmyBarton

Member
Jun 3, 2017
17
OK
The FC 2 was from the old testing kit that you compare color to match...I won't use that anymore. Since backwashing and rinsing a lot I had to replace some water so that may have helped the CYA. From my calculations using the pool math I put in another 3 gallons of 10% bleach which should raise it by 15 so plus 14 I should be at 29. I will retest in about 30 minutes and let you know. Can we swim with this high FC? If not what is a safe FC to swim at? Also when do I start testing PH to get an accurate reading?
 

AmyBarton

Member
Jun 3, 2017
17
OK
Okay just tested again, 45 minutes after adding 3 gallons of 10% and now I am up to 20 which should have been 29 according to the pool math. Total 27 gallons of chlorine added...I am starting to get worried this is going to damage my liner. What to do? Please read last post on questions too. Thank you so much!
 

frogabog

Gold Supporter
LifeTime Supporter
Jul 16, 2010
2,833
Portland, Oregon
Well, the good news is that at 55ppm CYA you only need to get to 22ppm FC instead of 28ppm FC. You could vacuum to waste or backwash some more and try to get the CYA down a bit more (add water). It looks like you've tipped the scale at least so you likely did get to your target at some point. The FC just got ate up doing it's job. Keep up the SLAM and add chlorine as the pool math shows. How often are you testing/adding?

You got this! Just keep on keeping on :~}
 

AmyBarton

Member
Jun 3, 2017
17
OK
I am now at 20 after putting 3 more gallons of 10% chlorine in. I tested it about 45 minutes after adding. So if I put one more gallon then that should do it. How long do I have to keep it at 28...with this heat it seems to go down quick? I have put in 28 gallons of 10% chlorine and its smells like chlorine.
 

frogabog

Gold Supporter
LifeTime Supporter
Jul 16, 2010
2,833
Portland, Oregon
I think you're hitting your target but by the time you test it's been eaten up. Pool math is rarely wrong. Assume if you add what it says to hit your target that it's in the pool. Your testing simply helps you know how much to add to get it back there. An hour is plenty of time to consume the chlorine while doing SLAM.

You can safely swim if you can see the bottom of your pool and your fc is is at SLAM level or lower. Your liner will be fine as well.

You're doing a great job with this!

Go swim!!
 

ajw22

Gold Supporter
TFP Guide
Jul 21, 2013
10,476
Northern NJ
We always round CYA up. If the dot disappears between 60 and 50 you call it 60. There is no CYA 55. Slam FC for CYA 60 is 24.
 

frogabog

Gold Supporter
LifeTime Supporter
Jul 16, 2010
2,833
Portland, Oregon
You're smelling chloramine. It's not a good smell, and it means you're killing algae.

If your cya is 55 now, pool math tells me your SLAM target is 22.

You will keep SLAMming till you pass the 3 criteria.

I'm not 100% with the rounding up crowd for cya just yet. I'm still struggling with an old school tfp mindset tho. I think you can tell the difference between 55 and 60 in the tube, and it will allow you to SLAM at 2ppm less fc.

I think your aiming for 28 the past couple days made a world of difference, which is why you cleared up so fast. If you only needed 24 at 60ppm cya, 28 was a bit much. But it worked nicely.

That being said, if you want to keep up your mad progress, by all means round up cya and target 24ppm fc.
 

Flying Tivo

Well-known member
Jan 24, 2017
1,108
Monterrey, NL, Mexico
Dont worry about gallons of bleach being consumed, just keep your levels to slam. Maybe those bottles of 10% are old and not full strength. Look for the date on the bottle, always try to buy the most recent ones.