I had some algae in my pool and started the SLAM process oh 6/5/24 after cleaning my filter’s cartridge. After a few days, the pool looked clear so I began looking at the SLAM exit criteria. No signs of algae, low CC, but I was failing the OCLT not by much so I continued the SLAM. Last night I did the test again and got a reading of 14.2FC, this morning my reading is 14.8FC. I know it’s not possible for FC to increase on its own so I’m at a loss. This is the 2nd time this has happened. I don’t know how to ensure my testing is more consistent than it is. I have read in these forums that testing can be inconsistent but wanted to check in with more experienced people as this is my first SLAM and I took over pool care just a few months ago. I don’t want to lose any progress made by stopping too soon. Thoughts?
OCLT test inconsistency
- Thread starter WaterwayHaven
- Start date
- Jun 22, 2014
- 52,088
- Pool Size
- 17888
- Surface
- Fiberglass
- Chlorine
- Salt Water Generator
- SWG Type
- CircuPool RJ-45 Plus
Welcome to TFP! 
It would help to know more about your pool and equipment by updating your signature. That can raise more questions. Did you have the pump running around the clock? Water sample from the same location, etc?
You are also using the Taylor (very precise) testing method with the 25 ml sample size. I would suggest using the 10 ml water sample with ONE generous scoop of powder. Mix until clear and take the drop count and divide it in half. So basically 24 drops would be an FC of 12.
It would help to know more about your pool and equipment by updating your signature. That can raise more questions. Did you have the pump running around the clock? Water sample from the same location, etc?You are also using the Taylor (very precise) testing method with the 25 ml sample size. I would suggest using the 10 ml water sample with ONE generous scoop of powder. Mix until clear and take the drop count and divide it in half. So basically 24 drops would be an FC of 12.
Thank you for the reply. I’ve updated my signature as suggested. I had the pump running overnight at lowest speed. Water sample from same location; elbow deep as far as I can reach on deep end. I have never used the 10ml water sample. Will try that today.Welcome to TFP!
You are also using the Taylor (very precise) testing method with the 25 ml sample size. I would suggest using the 10 ml water sample with ONE generous scoop of powder. Mix until clear and take the drop count and divide it in half. So basically 24 drops would be an FC of 12.
I have been doing the SLAM since 6/5/24. At the start my FC was 1.4, CYA 55 and PH 7.5. My water cleared pretty quickly so I did first OCLT on 6/6-6/7; CC and clarity were good, but FC was not. I have done the test 6 times and my results are all over the place; twice I’ve “gained” FC. I have ran out of R-0871 3 times since I started the SLAM. Through the entire process my FC has never been lower than 10 and my CYA has gone down to 45 (we had a lot of rain which allowed me to drain some water out of the pool a couple of times). I’ve attached my OCLT test results in case you have any thoughts you’d like to share.
Attachments
- Jun 22, 2014
- 52,088
- Pool Size
- 17888
- Surface
- Fiberglass
- Chlorine
- Salt Water Generator
- SWG Type
- CircuPool RJ-45 Plus
A couple things. First, plz post a couple pics of your pool at we can see the water and anything around it around from different angles. Second, FC testing should not be so eradic. Loss of FC is one thing, but going up means either the chlorine didn't have enough time to mix before grabbing the first sample, or the testing itself was not constant. I suspect you ran out of reagent because of the 25 ml size which required more reagent. Double check your testing as noted in my post above with the 10 ml size and let's see how the water looks.
- Jun 1, 2018
- 16,117
- Pool Size
- 26000
- Surface
- Vinyl
- Chlorine
- Salt Water Generator
- SWG Type
- Hayward Aqua Rite (T-15)
A large key to the oclt is darkness.
Aim for 30 minutes after sunset & 30 minutes before sunrise.
That’s about 9pm & 6 am at your house.
While that may account for some of your fc losses it doesn’t account for the increase in some of your tests so try doing the 10ml sample as suggested- there will be less drops to count/mis count & you’ll also save yourself some reagents.
Incriments of 0.5 ppm is plenty accurate for pool care
Aim for 30 minutes after sunset & 30 minutes before sunrise.
That’s about 9pm & 6 am at your house.
While that may account for some of your fc losses it doesn’t account for the increase in some of your tests so try doing the 10ml sample as suggested- there will be less drops to count/mis count & you’ll also save yourself some reagents.
Incriments of 0.5 ppm is plenty accurate for pool care
How long should I wait to test the water after adding chlorine? My pump is usually running at 1725rpms when I add chlorine and at 1150rpm overnight during SLAM.
I agree that results should not be so inconsistent. I have been as careful as I can be and consistent in the location of the sample collection and the powder and drops. I did the 10ml test during the day but thought the 25ml would be more precise for OCLT; didn’t want to overstate my results just to pass the test. I can do it both ways tonight and see how it compares. In your previous post you suggested using a generous scoop of powder; the test kit suggests using the 2 scoops for the 10ml just as for the 25ml; I followed the kit’s directions for what it’s worth.
Let me know if you’d like close-ups of any areas in the pool or my equipment.
Attachments
Thank you for the reply. To clarify, I need to collect sample water while it’s still dark out? I’ve collected when there is no direct sunlight.
- Jun 1, 2018
- 16,117
- Pool Size
- 26000
- Surface
- Vinyl
- Chlorine
- Salt Water Generator
- SWG Type
- Hayward Aqua Rite (T-15)
Testing 30 minutes after an addition is generally sufficient but if the pump is on low you may want to wait a little longer.
Did you inspect your light niche for algae?
Did you inspect your light niche for algae?
- Jun 1, 2018
- 16,117
- Pool Size
- 26000
- Surface
- Vinyl
- Chlorine
- Salt Water Generator
- SWG Type
- Hayward Aqua Rite (T-15)
No uv - thats the whole point of the test- to eliminate the possibility of uv consuming fc so you can tell if organics are consuming your fc.
I have not. I have been worried about messing something up. I may try to remove the light this afternoon.
- Jun 1, 2018
- 16,117
- Pool Size
- 26000
- Surface
- Vinyl
- Chlorine
- Salt Water Generator
- SWG Type
- Hayward Aqua Rite (T-15)
You want to be sure the power to the light is off at the source and if you’re unsure about how to remove it post an up close picture for more guidance.
- Feb 6, 2015
- 7,862
- Pool Size
- 12300
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- CircuPool RJ-45 Plus
- 10 ml sample - one generous scoop of powder.
- Are you using a SpeedStir type of stirring device?
- Hold the R-0871 liquid reagent bottle perfectly vertical. Dispense at a rate of one drop per second. Let the drops fully form on the tip - do not force them off or squeeze the bootle too hard.
- Don't be in a rush to complete the test. Be methodical.
Thank you.
How do you measure “generous”?
I use the back of a spoon to stir the powder and water
I do hold the bottle vertical; will take a look at the drop per second rate.
- Feb 6, 2015
- 7,862
- Pool Size
- 12300
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- CircuPool RJ-45 Plus
A heaping spoon full - slightly rounded.
Don't use the spoon to stir - swirl by hand. It's bewt to keep the spoon dry. Suggest you look into getting a SpeedStir or similar - it's a game changer for most of the tests.
It is important to allow the drops to fully form and drop from their own weight.
- Jun 22, 2014
- 52,088
- Pool Size
- 17888
- Surface
- Fiberglass
- Chlorine
- Salt Water Generator
- SWG Type
- CircuPool RJ-45 Plus
Water looks nice and I don't see anything in the water that could be potentially troublesome other than the light. Have you ever pulled it out and inspected behind it in the niche? If not, that might be something to do - with power OFF of course. Just pull the light and leave it on the decking. Gorgeous location and view you have. 
By the way, the 2-scoop thing is Taylor's 25ml sample size guidance. We typically recommend the 10 ml sample size (with one scoop) because it's still accurate and generally saves a little reagent. Easier math too.
By the way, the 2-scoop thing is Taylor's 25ml sample size guidance. We typically recommend the 10 ml sample size (with one scoop) because it's still accurate and generally saves a little reagent. Easier math too.
Thank you…to be clear, I’m not using the powder spoon to stir…just the handle of a regular spoon to stir the powder/water mix. I swirl by hand after adding drops. I’ll take a look into the SpeedStir. Will follow guidance on the drops.
Thank you. I will look into removing the light and checking out the niche. We bought the house for the viewWater looks nice and I don't see anything in the water that could be potentially troublesome other than the light. Have you ever pulled it out and inspected behind it in the niche? If not, that might be something to do - with power OFF of course. Just pull the light and leave it on the decking. Gorgeous location and view you have.
By the way, the 2-scoop thing is Taylor's 25ml sample size guidance. We typically recommend the 10 ml sample size (with one scoop) because it's still accurate and generally saves a little reagent. Easier math too.
which comes with its challenges. Just the other day, my dolphin cleaner picked up tiny fish while cleaning the pool.Attachments
- Jun 1, 2018
- 16,117
- Pool Size
- 26000
- Surface
- Vinyl
- Chlorine
- Salt Water Generator
- SWG Type
- Hayward Aqua Rite (T-15)
Update:
Thank you everyone for the advice. I followed the suggestions about testing times, using the 10ml water sample size, and allowing the reagent drops to fully form on their own with little squeezing. I passed the OCLT and discontinued SLAM and my numbers are still holding steady. My CYA is outside the ideal and TA is upper range of recommended so I’ll be working on those two next.
Thank you everyone for the advice. I followed the suggestions about testing times, using the 10ml water sample size, and allowing the reagent drops to fully form on their own with little squeezing. I passed the OCLT and discontinued SLAM and my numbers are still holding steady. My CYA is outside the ideal and TA is upper range of recommended so I’ll be working on those two next.
