New pool and first TF-100 Measurements - CYA 100+

Concord122

Member
Sep 11, 2019
22
Spring, TX
Hey guys and gals,

My TF-100 came today so when I came home my wife and I went to testing the pool and also our source water (kitchen tap). FYI, we have only owned the house and pool for two weeks.

Pool Measurements
pH:
7.8 - makes sense it is a bit high given the 3" chlorine tablets and no additional muriatic acid this week
FC: 8.5 ppm
CC: 2.5 ppm
TC: 11.0ppm
TA: 130 ppm
CH: 350 ppm
CYA: 100+. Couldn't see the black dot a few drops prior to the 100 graduation. Not too surprised given it is end of summer and the prior owners were always using 3" tabs and had pool guys who did unknown things. We shocked the pool once to get rid of algae. Algae treatment was 1/2 bottle of Banish and 3 lbs of shock from the pool store. I can't remember the name but it was not Burnout 73, but the more mild shock bc of our blue plaster.
Clarity: Very clear right now. No signs of algae.

Source Water
pH:
7.6
Cl: 3 ppm
CH: 50 ppm
TA: 220 ppm - did it twice, as I was surprised it could be higher than the pool water. Our water comes from Lake Conroe.

Any recommendations going forward? We would like to keep using the pool, at least this weekend since we have guests coming. Pool season is pretty long here (100 degrees last week) and we have a heater as well. Is a partial or full drain and re-fill in order?

Thanks for your help!
 

jimbethesda

Gold Supporter
Jul 2, 2018
269
Austin, TX
In order to get your real CYA level, you’ll have to do a diluted CYA test. Use 1/2 pool water, 1/2 tap water and test again. Double your result. If you get 200, you’ll have to further dilute it (1/4 pool water, 3/4 tap).

Once you get your real value, you’ll know how much you need to drain your pool by.
 

Concord122

Member
Sep 11, 2019
22
Spring, TX
In order to get your real CYA level, you’ll have to do a diluted CYA test. Use 1/2 pool water, 1/2 tap water and test again. Double your result. If you get 200, you’ll have to further dilute it (1/4 pool water, 3/4 tap).

Once you get your real value, you’ll know how much you need to drain your pool by.
Diluted CYA test (7.5 mL of pool, 7.5 mL of tap) gave us a reading of 90 ppm (45 x 2). I think that is pretty consistent with the results of the first test since it turned cloudy just about at 100 ppm.
 

duraleigh

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Apr 1, 2007
32,863
Sebring, Florida
Clear water and no sign of algae is very good. The cc's of 2.5 is too high.

I would suggest you keep your FC up around 10-12 (with that 90 CYA) and test for CC's every day until they go down..

You really want the CC's to be .5 ppm or zero so let's see what those future tests bring.

I would also suggest you perform an OCLT and post those results.

Normally, we would suggest a SLAM to clear the CC's out of your pool but it would take a TON of chlorine and you have clear water and it's late in the season.

All that adds up to a pool that you need to monitor carefully and, if your cc's don't start heading lower right away, then you will need to SLAM regardless.
 

Concord122

Member
Sep 11, 2019
22
Spring, TX
Thanks, Duraleigh. I will take the measurements again tomorrow morning when I wake up around 0615 and update the results. Am I correct that I should not add any chemicals tonight?

I also went to the store tonight and bought 3x gallons of HD liquid chlorine, some muriatic acid, Borox, and a 12lb bag of baking soda. If we need more, its only a 10 minute drive.
 

Concord122

Member
Sep 11, 2019
22
Spring, TX
Let me run the test again tonight and Saturday morning. I found the more detailed instructions for the FAS-DPD test FAS-DPD Chlorine Test - Trouble Free Pool and am not confident in the numbers provided yesterday. I think the hard part is determining when is the water "completely clear." When I did it this morning, I was up to 35 drops and it of R-0871 and it still had a pink tint to it. It should look as clear as the original pool water, right?
 

Concord122

Member
Sep 11, 2019
22
Spring, TX
Are you using the Speedstir Magnetic Stirrer ?

It makes a difference in the repeatability of the testing endpoint.
No, I didn't order originally with my test kit but it sounds like everyone really likes it. I will order one today.

Also, just saw a few spots of algae on the walls, mainly around the built in benches in the corner. Brushed it off. Should I add a bit more chlorine?
 

ajw22

Gold Supporter
TFP Guide
Jul 21, 2013
11,678
Northern NJ
No, I didn't order originally with my test kit but it sounds like everyone really likes it. I will order one today.

Also, just saw a few spots of algae on the walls, mainly around the built in benches in the corner. Brushed it off. Should I add a bit more chlorine?

See post #4. Your CCs indicated you have algae in the water.

A little more chlorine will not make a difference. It will take a lot of chlorine with the SLAM Process to clear the algae.
 

Concord122

Member
Sep 11, 2019
22
Spring, TX
Right. He also said a SLAM would take too much chlorine given the high CYA level in the pool. Sounds like I will need to partially drain the pool to get the CYA down to the right level and then SLAM?
 

ajw22

Gold Supporter
TFP Guide
Jul 21, 2013
11,678
Northern NJ
Right. He also said a SLAM would take too much chlorine given the high CYA level in the pool. Sounds like I will need to partially drain the pool to get the CYA down to the right level and then SLAM?
That is the long term fix to more easily manage your water chemistry.

You can drain or do a Water Exchange if you have the water available.
 

frogabog

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Jul 16, 2010
2,833
Portland, Oregon
Borax works great on cloth diapers. Helps them come out nice and white, and very fresh (clean!).

Also, I wanted to note that the trichlor tablets are acidic, so using them actually helps keep your pH lower. But stop using them. No more CYA for you! :cool:
 

duraleigh

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Apr 1, 2007
32,863
Sebring, Florida
: 220 ppm - did it twice, as I was surprised it could be higher than the pool water.
Forgot to mention this. With a brand new test kit and VERY fresh R-0009, there is a phenomenon wherein your TA reads too high.

It's caused by static that somehow develops between the liquid and the plastic bottle. Wiping the dropper tip with a damp cloth in between drops eliminates this and you will get a low TA reading. This will go away in a week or two.
 

Concord122

Member
Sep 11, 2019
22
Spring, TX
Forgot to mention this. With a brand new test kit and VERY fresh R-0009, there is a phenomenon wherein your TA reads too high.

It's caused by static that somehow develops between the liquid and the plastic bottle. Wiping the dropper tip with a damp cloth in between drops eliminates this and you will get a low TA reading. This will go away in a week or two.
Ah, okay! That makes some sense. We did follow the directions to wipe the tip between drops with a damp paper towel. Hopefully it stabilizes as you say.

We will work on doing a water exchange on Sunday after our guests leave. Our pool is currently 86 degrees and the source water is definitely cooler. I will re-measure again to see which way to position the pump and hose in the pool. Is this a suitable pump? 1/6 HP Submersible Utility Pump 1600 GPH