Beginner with TFP method - when to test after pool store opened?

splashpad

Bronze Supporter
Aug 2, 2017
2,708
SE Kansas!
An update - so last night I:
  • backwashed the filter taking psi from 20 to 16 (but didn't deep clean, was too worried I'd bork the system)
  • added 3 gallons liquid 12.5% sodium hypochlorite to get to 20 SLAM level (per Pool Math I needed .5 gallons more, but I wanted to be conservative, funny considering results below)
  • brushed pool, left pump running
  • tested 2 hrs later and free chlorine was 31 (!)
  • I tested early this morning (7 hours later) and FC was 29
  • pool looks slightly more blue/clear this morning, and I just brushed it
Clearly I got something wrong which made the amount of chlorine added way too much. I did the chem tests a couple times to be sure, and the pool volume I could be off by ~2000 max I calculate.

Reading about what to do if FC is too high I'm seeing that I should probably let it settle on it's own as there aren't great ways to get it down quickly and it's not terrible. Next 4 days are going to be very hot and sunny, so it should go down. Will test FC again in a couple hours and post back.
Keep the pump running 24/7, your FC should come down pretty quickly since you weren't able to deep clean the sand yet (you're prob ok there)
What are the actual measurements of your pool? (length/width, max depth, min depth?)
 

splashpad

Bronze Supporter
Aug 2, 2017
2,708
SE Kansas!
  • We don't know for 100% certainty the pool type and volume, as we can't get in touch w/ former owners. The pool service yesterday said it was fiberglass, and it's roughly 16x40 (not sure depth yet but about 3-8 feet) so I calculate ~20k gallon volume. How important is it for the chemicals that we have 100% accuracy on both of these? (especially volume)
To refer back to this, The closer the better, mostly so there isn't overshooting. It's much better to need a little more.
 

splashpad

Bronze Supporter
Aug 2, 2017
2,708
SE Kansas!
  • added 3 gallons liquid 12.5% sodium hypochlorite to get to 20 SLAM level (per Pool Math I needed .5 gallons more, but I wanted to be conservative, funny considering results below)
  • tested 2 hrs later and free chlorine was 31 (!)
Double check the right strength of bleach is showing in PoolMath
 

jlsmith123

Member
Jun 11, 2020
20
Northeast Ohio
Thanks @splashpad. Clear I should undershoot rather than overshoot with the chemicals, a good lesson. Pump will run 24/7 until under control.

Measurements are 16' wide x 40' long, min depth is ~3' and max is ~5' to 6. My error here can come from 1) sloped sides 2) the depths are approx, as I haven't gone inside the pool yet to measure so it's approximation from the pool deck using a metal rod and 3) we have stairs at both ends. I'm guessing I'm off here by a couple thousand.

Bleach strength was ok in the app. I have 12.5% sodium hypochlorite - is it correct I select "bleach" from the chemical list for any type of liquid sodium hypochlorite?

Thanks again
 
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splashpad

Bronze Supporter
Aug 2, 2017
2,708
SE Kansas!
Once your FC goes down, just use partial doses and verify FC levels after 30min or so, until you can get honed on the size!

Yes! (selecting 'bleach'). It's because before COVID plain household bleach was often cheaper or easier to get than liquid pool chlorine.
 
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IceShadow

Gold Supporter
TFP Guide
Jun 8, 2019
2,177
Milwaukee, WI
If you do want to deep clean the sand, you'd take off the union at the heater and (I hope you have one) at the pump. With those two unions off, the piping is disconnected from the system. Remove the collar at the bottom of the MPV by undoing the thumb screw all the way, and you can wiggle the whole top off the standpipe with all the waste, in, and out pipes still attached. I did something similar last year. (Now I have cut and put unions on everything to make it easier to disconnect closer to the filter.)
 
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TheDeuce

Gold Supporter
Jul 9, 2019
135
Winnipeg, Manitoba
An update - so last night I:
  • backwashed the filter taking psi from 20 to 16 (but didn't deep clean, was too worried I'd bork the system)
  • added 3 gallons liquid 12.5% sodium hypochlorite to get to 20 SLAM level (per Pool Math I needed .5 gallons more, but I wanted to be conservative, funny considering results below)
  • brushed pool, left pump running
  • tested 2 hrs later and free chlorine was 31 (!)
  • I tested early this morning (7 hours later) and FC was 29
  • pool looks slightly more blue/clear this morning, and I just brushed it
Clearly I got something wrong which made the amount of chlorine added way too much. I did the chem tests a couple times to be sure, and the pool volume I could be off by ~2000 max I calculate.

Reading about what to do if FC is too high I'm seeing that I should probably let it settle on it's own as there aren't great ways to get it down quickly and it's not terrible. Next 4 days are going to be very hot and sunny, so it should go down. Will test FC again in a couple hours and post back.
I had the exact same issue with my now nearly-completed SLAM. I was meticulous in adding 10.8% liquid chlorine as recommended by Poolmath to the millilitre but I still ended up with an FC level way over my target. My best guess is that I, in using my pool installer volume spec in litres, may have used a faulty conversion from litres to gallons. I've since learned how to change Poolmath to Metric and will take a 'add less, add more later if needs be' approach.

We're doing our first SLAM simultaneously. I hope yours goes as well as mine is - I think I'm pretty much done.

One piece of advice I'll share, having learned from my first go round. If you have a UV sanitizer in your system, turn it off. I kept mine on 24/7 not knowing that it would consume FC during the OCLT. I couldn't understand why I was losing FC overnight when my CC's were near zero and the clarity was pretty darn good.


m.
 

jlsmith123

Member
Jun 11, 2020
20
Northeast Ohio
Thanks @IceShadow. Will take a closer look tonight at the unions.

Congrats @TheDeuce on nearly completing your first SLAM successfully. Hope I’m not too far behind. I’ll check re the UV sanitizer I have no idea about that.

For testing today - I just tested and I’m at 22 FC and 5 CC. I’ll test again late evening and then likely add some more liquid chlorine to make sure level remains high enough overnight. Is a drop of 8 ppm FC in ~12 hours indicative of something out of ordinary? The pool isn’t that dirty, almost no organic matter and already looking better. I’ll post an end of day pic later.
 

TheDeuce

Gold Supporter
Jul 9, 2019
135
Winnipeg, Manitoba
Thanks @IceShadow. Will take a closer look tonight at the unions.

Congrats @TheDeuce on nearly completing your first SLAM successfully. Hope I’m not too far behind. I’ll check re the UV sanitizer I have no idea about that.

For testing today - I just tested and I’m at 22 FC and 5 CC. I’ll test again late evening and then likely add some more liquid chlorine to make sure level remains high enough overnight. Is a drop of 8 ppm FC in ~12 hours indicative of something out of ordinary? The pool isn’t that dirty, almost no organic matter and already looking better. I’ll post an end of day pic later.
I don't know if it's 'out of the ordinary' but I had an OCLT drop from 33 to 26 (7 ppm) on the night of the 12th to the 13th, but I was slow in getting the AM reading. The sun rises early up here and I have no yen to drag myself out of bed at 4:45 AM...


m.
 
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jlsmith123

Member
Jun 11, 2020
20
Northeast Ohio
5 or 0.5?
The CC level was 5 (it took 10 drops for the 10 ml sample to turn clear). So I guess consuming a lot of organic matter.

@TheDeuce ok so you’ve seen a similar drop in FC. My pool did have a lot of sun today. Only reason I get up early (and can do pool stuff late) is because we have an infant. May as well do something useful while I’m awake anyway. 🙃

Pics of current status attached, looks way more clear today I can now see small dirt remnants in bottom which were very difficult to see 24 hrs ago.
 

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IceShadow

Gold Supporter
TFP Guide
Jun 8, 2019
2,177
Milwaukee, WI
A lot of pool companies add ammonia-based algaecide. Ammonia will react with FC to make CCs.

Don’t bother going over SLAM level. You want to be at SLAM level as often as you can.
 
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IceShadow

Gold Supporter
TFP Guide
Jun 8, 2019
2,177
Milwaukee, WI
Not sure if this has been recommended yet but if you get stalled on improvement on clarity you could deep clean the sand filter.

Sand filters do take time to clear. So long as you see improvement in the clarity day to day (check the steps and that's usually a good indicator) then you're on the right path. Backwash whenever your filter gets to 25% above standard "clean" pressure.

It's safe to swim in a pool that has FC up to SLAM levels and that you can see the entire bottom of.
 
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jlsmith123

Member
Jun 11, 2020
20
Northeast Ohio
Took a couple more tests today, needed to add chlorine once to get it back up to slam level of 20 after the high sun peak.

Ended day at 20 FC and .5 CC, that was my second .5 CC reading so seems CC is decreased significantly from yesterday.

Pool is so much more clear and blue now. Pic attached - I need to take them from same vantage point to better track. But we tried it out this evening for a quick first swim! Doesn’t smell like chlorine and feed fine.

We’ll see how much FC I lose tonight.

I don’t want to count my chickens before they hatch, but so far this method is working. Thanks for all the help.
 

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jlsmith123

Member
Jun 11, 2020
20
Northeast Ohio
An update as I may be stuck. So my water is very clear, and my CC has been stable at .5 for two days. I’m stuck at the OCLT, last two nights I did it and:

Tuesday night I lost 4 FC overnight —->
-Tuesday night: FC 20, CC .5
- Weds morning: FC 16, CC .5

Wednesday night I lost 5 FC overnight —->
- Weds night: FC 21, CC .5
- Thursday morning: FC 16, CC .5

Do I just keep maintaining slam levels of FC, daily brush, vacuum and backwash as needed? Or do I need to do something else?

I’d like to stop running filter 24/7 soon as it’s been on full time for a week now.
 

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