First steps to gaining control/balance?

Scallion

Member
Jul 15, 2019
8
Melbourne
Essential stats:
Melbourne, Australia
Approx 45,000-50,000L (approx 10,000-11,000 gallon)
In ground pool (plaster, quartz finish)
Sand filter, only 6 month old
Unsure of pump specs
Test kit: Clear Choice Labs
Using SWG

Test Results (latest available)
FC > 45 ppm
CC = unclear, see below
pH 7.6 (added 500mL muriatic acid ~32%, yet to retest)
TA: 200
CH: 340
CYA: 95 ppm
Water: Clear

---

Pool on a recently purchased property. I am a very new owner and trying to get the chemistry in balance. Important history and information below:

1. We have access to the pool Sat/Sun on weekends, once a week, in the interim. I brush, manually vacuum, skim, and empty pump/skimmer baskets weekly.
2. The pool was without power because of an electricity company issue on change over. Approximately two weeks without turnover of water.
3. Noticed three small black spots at different parts of pool. Likely to be black/blue-green algae. These have been brushed with particular intensity every week, but not daily as would be optimal. In the past 4 weeks they have not been going or spreading.
4. Two weekends ago we took a sample to the pool store for testing (before getting Clear Choice Labs test kit). Mentioning the black spots, the pool tech recommended shocking with 2kg (4.4lb) of Ezi-Chlor (trichlor), and an algaecide (1L).
5. I believe this caused a significant rise in CYA, which now sits at 95. Unsure whether this test result is reliable due to high levels of FC.
6. Assuming there might be a drop of about 2 ppm FC per day (there is minimal sunlight locally as we are in the dead of winter), I have left the SWG at 0 percent for this week to help bring FC down to more appropriate levels. Pump is running 5 hours per day to keep circulation.
7. I don't know where to start! All tests in my test kit (recommended kit for Australians on this forum) are documented as being unreliable at FC concentrations higher than 10 ppm.
8. Stopped testing FC at 45 ppm as I was afraid of depleting the titration agent in the brand new testing kit!

Obviously, I want to take matters into my own hands now, but not sure what steps to take from here.

Should I: drain the pool enough to reduce CYA to between 70-80 ppm, refill, then let FC reach below 10 ppm, re-test and adjust from here? I assume some amount of drainage will be inevitable, as there doesn't seem to be another way to reduce CYA, and at 95 it is so high I am concerned it will impact on the chlorine effectiveness.

I'm also finding it difficult to figure out how to address the three black spots in the pool given I have only the weekend opportunities to scrub and monitor.

Any advice on the necessary steps to get on the path to balanced chemistry would be greatly appreciated!

We were also sold some Beautec Scale-Stain-Scum controller, and some Anionic Polymers, but I don't want to add these unless they are necessary and the rest of the chemistry is looking acceptable.
 

ajw22

Gold Supporter
TFP Guide
Jul 21, 2013
9,832
Northern NJ
Welcome to TFP and congratulations on the new house and pool.

When CYA tests over 90 you need to follow Step 8 in the test procedures below:


8. If your CYA level is 90 or higher, repeat the test adjusting the procedure as follows:
  1. Fill the mixing bottle to the lower mark with pool water.
  2. Continue filling the mixing bottle to the upper mark with tap water.
  3. Shake briefly to mix.
  4. Pour off half of the contents of the mixing bottle, so it is again filled to the lower mark.
  5. Continue the test normally from step 2, but multiply the final result by two.
How do you plan to chlorinate the pool?
 

Scallion

Member
Jul 15, 2019
8
Melbourne
Thank you, and thank you kindly for your reply!

I wasn't aware of this method. I will retest CYA on Saturday, assuming that this method works with the Clear Choice equipment (I assume that the reagent would be equivalent to that found in Taylor kits).

We chlorinate using a SWCG (model should now be in my signature). I have 13 percent liquid chlorine on hand in case I need to shock in the future. I had it running too long at too high in the last week (5 hours per day) which I suspect contributed to the high FC levels.

Thank you all for ongoing advice and this wonderful resource!
 

frogabog

Gold Supporter
LifeTime Supporter
Jul 16, 2010
2,833
Portland, Oregon
Do you have a wire brush to try to tackle those black/blue spots? The regular brush won't be able to break through black algae spots so that the FC can get to it and kill it.

If they are indeed black algae, your high FC isn't an actual problem. SLAM level for 95ppm CYA is 37ppm FC. So... 45ppm isn't really that far off. If you think it's black algae, I'd turn that SWG back on and let it work on it. I know some will say not to use the SWG during SLAM, but since you don't have access to it daily, and it seems to do a bang up job of chlorinating... letting the pool go at high FC seems like a decent option in your situation.

So, it's not very cold in the winter in Melbourne, eh? (since the SWG is working)
 

ajw22

Gold Supporter
TFP Guide
Jul 21, 2013
9,832
Northern NJ
SLAM level for 95ppm CYA is 37ppm FC.
You cannot measure CYA of 95 ppm and you cannot interpolate SLAM FC levels between 90 and 100 CYA. The distance between the lines on the CYA test are logarithmic, not linear. Halfway between lines is not 5. You can't judge what it is. That is why we round up. If the dot disappears between 100 and 90 you call it 100. The SLAM FC level is then 39.

I doubt the CYA is really 90 to 100. It is likely higher and the reason to do the dilution test to determine if a drain or water exchange is the best action before the SLAM Process
 

frogabog

Gold Supporter
LifeTime Supporter
Jul 16, 2010
2,833
Portland, Oregon
You cannot measure CYA of 95 ppm and you cannot interpolate SLAM levels between 90 and 100 CYA. The distance between the lines on the CYA test are logarithmic, not linear. Halfway between lines is not 5. You can't judge what it is. That is why we round up. If the dot disappears between 100 and 90 you call it 100. The SLAM FC level is then 39.

I doubt the CYA is really 90 to 100. It is likely higher and the reason to do the dilution test to determine if a drain or water exchange is the best action before the SLAM Process
Yes, I understand. I was just popping numbers into Pool Math for a general idea to make a point. I will refrain from using 5s in all future popping... :censored:
 

Scallion

Member
Jul 15, 2019
8
Melbourne
So, it's not very cold in the winter in Melbourne, eh? (since the SWG is working)
It would be very rare to dip below 30F even in the dead of winter in Melbourne! In any case the manual doesn't seem to indicate any issue with water temps.

Do you have a wire brush to try to tackle those black/blue spots?
I don't but will gladly get one - but can I safely use this on a quartz render finish without damaging it? The pool store provided no guidance on this, so I'm hesitant.

I doubt the CYA is really 90 to 100. It is likely higher and the reason to do the dilution test to determine if a drain or water exchange is the best action before the SLAM Process
Thank you for this! Really clear guidance. This is my first step. If the dilution test shows wildly high numbers, then I'll likely need to drain to 80 CYA, fill, circulate the water, and retest before doing anything else. And this time I'll know to round up :)
 

frogabog

Gold Supporter
LifeTime Supporter
Jul 16, 2010
2,833
Portland, Oregon
Insofar as your quartz render finish... I haven't a clue what that exactly is.

I'm sure someone here will know if that's ok or not. Maybe there's a special super stiff brush that's not wire made for such purposes?
 

Scallion

Member
Jul 15, 2019
8
Melbourne
Insofar as your quartz render finish... I haven't a clue what that exactly is.
I'll be honest - I have no idea either! :p
I believe it is crushed concrete and quartz and is added to a plaster? I'm unsure. As we didn't build ourselves, it is mostly a guess.

I would jump in the pool to confirm it's algae with a fingernail scrape, but it's definitely a little too chilly for that at the moment...
 

frogabog

Gold Supporter
LifeTime Supporter
Jul 16, 2010
2,833
Portland, Oregon
Maybe you could you attach a spoon to the end of a pole and try to scrape some up? Maybe sharpen it up some? FWIW, normal algae won't grow under 50F as far as I know.
 

Scallion

Member
Jul 15, 2019
8
Melbourne
Update.

CYA 80
FC 42.5
CC 0
Salt 5400 (recommended 3750)

I retested CYA yesterday and got a fairly consistent 80. I'm not sure if perhaps I was misreading the test last week and getting used to my kit. I will retest CYA shortly.

Good news is I completed the FC test and measured 42.5 with a CC of 0. This is promising. Given continued high FC though I don't know how reliable other tests are.

Salt is about 1500 ppm higher than the ideal range. Given high chlorine levels at the moment I am running the pump with the SWG set to 0%

Also noticed some white dots this week, and have added 1L of Beautec in case it is a calcium build-up. Was due this month anyway.

I've taken photos of the mystery black spots and attached to this post - one of each. I scraped with the end of the pole minus attachment - nothing came off. Could this actually be a metal stain instead?

Given I've confirmed the pool is either concrete or plaster with a special finish, should I metal brush them anyway and see what happens?

Here's the spots:

IMG_20190804_131457.jpgIMG_20190804_131358.jpgIMG_20190804_131528.jpg

Thanks in advance for the advice, I might slowly learn to hate the pool less and perhaps even love it some day soon...:)
 

Scallion

Member
Jul 15, 2019
8
Melbourne
Update:
After about a month with the SWG switched off (and the pump still circulating water daily for 5 hours), FC has almost drifted down enough that I can start to get a proper measure on my chemicals!

Latest results:
FC: 14.5
CC: 0.5
CH: 175
TA: 175
CYA: 80 (after going back to the drawing board, learning to better interpret the CYA test, testing and retesting, I am satisfied that CYA is actually well balanced now)

I have noticed two things:

1. Beginning to develop some white scale at the waterline, which turns into a slick layer of thin white on the surface when brushed. I assume this is calcium (as the pool has a few white spots which are likely calcium deposits). This scale and sheen disappears when I add the regular dose of acid. Is it safe to assume this is calcium, and that when it appears pH is too high? (I should be able to get an accurate pH reading this weekend at last.)

2. The black spots, pictured above, have not really changed at all, despite paying particular attention to them when scrubbing with a nylon brush, and despite a month of high FC levels. Could it be that this is not black algae, but something else (such as metal staining)?

As a final question, do I need to worry about a CC of 0.5? I assume this level is in response to leaf and other organic matter in the pool. I am finally in the position where I can do an overnight chlorine loss test, so is it advisable to remove all matter, circulate water, and test for FC loss overnight?

Thank you for the sagely advice - two months in and still a steep learning curve, but hopefully I'm making progress.,
 

ajw22

Gold Supporter
TFP Guide
Jul 21, 2013
9,832
Northern NJ
C.C. of 0.5 comes from normal chlorine sanitation. It does not indicate a problem.

With FC above 10 you can’t get a good pH test by chemical methods. When your FC gets below 10 check your pH. High pH can cause high CSI and cause the scaling you see.
 

Scallion

Member
Jul 15, 2019
8
Melbourne
C.C. of 0.5 comes from normal chlorine sanitation. It does not indicate a problem.

With FC above 10 you can’t get a good pH test by chemical methods. When your FC gets below 10 check your pH. High pH can cause high CSI and cause the scaling you see.
Sounds like that's my next step - hope that we're below 10 FC this weekend, check pH (and see if any scaling has reformed) - thank you.

The mystery of the black spots will continue for now I think! 🤔