High FC and pH / Unstable CYA

[Mortal-Man]

Hi, there - looking for some help … I’ve been struggling with a faulty SWG and low FC (as well as a subpar pool service company). That’s now resolved (I took over the service myself) and I’m working to get back into balance. I cannot seem to get the pH in a range (even using 4 drops instead of 5) lower than ‘dark pink’. I doubled the recommended dose of acid from Pool Math (1 gal yesterday) - still no dice. Now my ever-loving patch of black algae is starting to come back to life. As for CYA, I added 5 gal of liquid stabilizer and the CYA was at 90 3-days later. Now 10 days after, my CYA is at 50. I thought that stayed in the water longer? Pool math recommends 2 more gallons; wanted to get some advise before proceeding.

What should I be doing differently?

FC: 9.0
PH: 8.2
TA: 130
CYA: 50 (dropped from 80 the week prior)
Calcium: 550
Salt: 4200 (pool tech was adding salt based on the panel instead of running an actual test)
CSI: 0.91
Test kit: TF-PRO

 

[Texas Splash]

CYA (stabilizer/conditioner) does indeed remain in the water longer. The only way it would drop significantly is if you exchanged water or have a pool leak. If you had a leak, you would also see a drop in salt and perhaps CH if you refilled with soft water. If those other items are not changing, it's more than likely a testing issue.

Your FC is just under 10, but perhaps close enough to where it's messing with the pH color tint. Maybe let the FC fall to about 7-8 and try again. Your pH will also climb quickly with a TA of 130. My recommendation for that issue is to use enough muriatic acid to lower the pH from 8.2 down to 7.0-7.2. Then when the pH creeps up high again, repeat with acid. Each time you lower the pH from 8.2 to 7.2 it should lower the TA a bit. Continue that routine until you get the TA down to about 60. That should help tremendously.

 

[Bperry]

Hi, there - looking for some help … I’ve been struggling with a faulty SWG and low FC (as well as a subpar pool service company). That’s now resolved (I took over the service myself) and I’m working to get back into balance. I cannot seem to get the pH in a range (even using 4 drops instead of 5) lower than ‘dark pink’. I doubled the recommended dose of acid from Pool Math (1 gal yesterday) - still no dice. Now my ever-loving patch of black algae is starting to come back to life. As for CYA, I added 5 gal of liquid stabilizer and the CYA was at 90 3-days later. Now 10 days after, my CYA is at 50. I thought that stayed in the water longer? Pool math recommends 2 more gallons; wanted to get some advise before proceeding.

What should I be doing differently?

FC: 9.0
PH: 8.2
TA: 130
CYA: 50 (dropped from 80 the week prior)
Calcium: 550
Salt: 4200 (pool tech was adding salt based on the panel instead of running an actual test)
CSI: 0.91
Test kit: TF-PRO

If you have algae, you do not want to add any more stabilizer.

 

[Mortal-Man]

CYA (stabilizer/conditioner) does indeed remain in the water longer. The only way it would drop significantly is if you exchanged water or have a pool leak. If you had a leak, you would also see a drop in salt and perhaps CH if you refilled with soft water. If those other items are not changing, it's more than likely a testing issue.

Your FC is just under 10, but perhaps close enough to where it's messing with the pH color tint. Maybe let the FC fall to about 7-8 and try again. Your pH will also climb quickly with a TA of 130. My recommendation for that issue is to use enough muriatic acid to lower the pH from 8.2 down to 7.0-7.2. Then when the pH creeps up high again, repeat with acid. Each time you lower the pH from 8.2 to 7.2 it should lower the TA a bit. Continue that routine until you get the TA down to about 60. That should help tremendously.

Great, thanks for the response. I don’t think I have a pool leak; I agree with an issue with testing (‘when the spot disappears’ is a bit more subjective than I prefer, but I’ll get the hang of it).

How much acid/what strength do you recommend? I was thinking of adding a gallon of 14.5% a day until within range …

 

[Mortal-Man]

If you have algae, you do not want to add any more stabilizer.

Got it. So I understand moving forward, what part of the stabilizer promotes algae?

 

[Newdude]

How much acid/what strength do you recommend?

Lower it 0.4 at a time. Mix for 20 mins and retest. Repeat as necessary until you're in the 7s.

Your choice if you want to buy twice as much 14.5% for less fumes, or use full strength.

what part of the stabilizer promotes algae?

None.

It buffers the FC and for every 10 CYA you need proportionately more FC to sanitize at the same level. Adding 10 ppm CYA raises the slam target +4. It gets out of hand quickly.

 

[Mortal-Man]

Lower it 0.4 at a time. Mix for 20 mins and retest. Repeat as necessary until you're in the 7s.

Your choice if you want to buy twice as much 14.5% for less fumes, or use full strength.

None.

It buffers the FC and for every 10 CYA you need proportionately more FC to sanitize at the same level. Adding 10 ppm CYA raises the slam target +4. It gets out of hand quickly.

View attachment 608478

Thanks again for the help!! I progressively added a total of 2 gallons of 31.4% muriatic acid until my pH got down to ~7.0. I tested 3 days later and pH is now ~7.6 and TA is 80. FC is 18; I’m pulling the SWG back an hour’s run time to accommodate.

I feel like I’m finally making headway and getting the chemistry balanced. Thanks a million to you and TFP for helping me get there!

 

[mknauss]

Thanks a million to you and TFP for helping me get there!

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[Newdude]

until my pH got down to ~7.0

You aim for *the* 7s, not 7.0 itself. Many find it remains stable in the high 7s and it bounces back quick from a low 7. When it hits 8+, dose down to 7.6 or 7.8.

It will rise a little quickly for now but as you do your thing the TA will drop and eventually help keep the Ph down.

 

[Mortal-Man]

You aim for *the* 7s, not 7.0 itself. Many find it remains stable in the high 7s and it bounces back quick from a low 7. When it hits 8+, dose down to 7.6 or 7.8.

It will rise a little quickly for now but as you do your thing the TA will drop and eventually help keep the Ph down.

Got it - thanks!!