Help with further balancing salt water pool

[TxFireAg]

Hi all! I've been trying to get my mother's SWG pool in order this summer so it's a bit more sustainable for her to maintain between when I visit. The stats in my profile should be accurate but here's a rundown of the system and current chemical levels:

~15,300 gal salt water pool
Gunite and plaster (in ground)
Location: Houston (super hot right now)
Sun: in full sun from about 11 - 5
SWG: Circupool COre35 running at 50% from 8-6 7 days/wk

Latest test:
FC: 1.5
CC: 1.0
TC: 2.5
pH: 7.8
TA: 110
CH: 300
CYA: 47
Salt: 3300
Temp: 85.1
CSI: 0.18

pH has been high (8.3 avg) for months and I've been dumping in Muriatic acid to combat that. For whatever reason, I'm having to add about double what Pool Math suggests to get pH to start trending down. My plan was to lower pH to 7.2 and then aerate (with hot tub blower) up to 7.8 to lower TA at the same time. So far, 7.8 is the lowest I've gotten the pH without dumping over a gallon of acid in.

Likewise, CYA has been low (averaging 20). Pool Math suggested 2 gallons of conditioner which only raised it to ~50 as we see now. Apparently I need to go buy more. I was also noticing some light green algae on the walls which I was able to brush off easily.

I was doing some reading and it seems that since my pH is high, CYA is low, and TA is high, a chlorine tablet might do exactly what I need. I have some chlorine tabs here (don't know why) that I can certainly use but I wanted to run this plan by the brain trust first. Is there anything I'm missing with using a chlorine tab?

If the chlorine tab isn't the best thing to do, what's a better method? And why does it seem like I need to dump 2-3 gal of Muriatic acid in to get pH down to 7.2 to aerate back up?

Thanks!

 

[PoolGate]

Why are you keeping free chlorine so low? This is the root cause of 90% of pool issues. My advice is increase the chlorine level to at least 5. How are you measuring CYA btw. There is no "47" on the scale.

 

[TxFireAg]

Why are you keeping free chlorine so low? This is the root cause of 90% of pool issues. My advice is increase the chlorine level to at least 5. How are you measuring CYA btw. There is no "47" on the scale.

As an engineer I should know better than to interpolate between resolution markings on the instrument but alas…it’s what I did. CYA is slightly above the “50” approaching the “40” so I eye-balled a 47. That’s all the science that went into that.

I’m not intentionally keeping the FC so low. I’m just trying to nudge it higher but I’m finding I have to set the SWG way higher than pool math is recommending. Similar to how I’m finding myself having to add more chemicals. I’ll bring the SWG up and start with that.
Edit: there’s also a noticeable trend over the last 6 months of CYA dropping (down to 20) and FC dropping with it. Perhaps I’m not adding enough conditioner to maintain CYA?

 

[PoolGate]

As an engineer I should know better than to interpolate between resolution markings on the instrument but alas…it’s what I did. CYA is slightly above the “50” approaching the “40” so I eye-balled a 47. That’s all the science that went into that.

I’m not intentionally keeping the FC so low. I’m just trying to nudge it higher but I’m finding I have to set the SWG way higher than pool math is recommending. Similar to how I’m finding myself having to add more chemicals. I’ll bring the SWG up and start with that.

CYA is more a logarithmic scale. So just go all the way to the next (higher) number when in between. The rest of your numbers are not bad. You could try to lower T/A but it is a long process that requires frequent acid additions and constant aeration.

 

[hexabc]

Use liquid chlorine to get FC to 6 - 7 ppm level and then have SWG maintain that level.

 

[hexabc]

Use liquid chlorine to get FC to 6 - 7 ppm level and then have SWG maintain that level.

And do not add CYA anymore. If you have algae you will need to go through the SLAM process with FC = 40% of CYA.

 

[TxFireAg]

And do not add CYA anymore. If you have algae you will need to go through the SLAM process with FC = 40% of CYA.

It’s like y’all knew what was coming. Water turning green and CYA up to 100. I learned a lesson here. Now to begin the SLAM…

 

[SoCalTFP]

It’s like y’all knew what was coming. Water turning green and CYA up to 100. I learned a lesson here. Now to begin the SLAM…

Might wanna pack a bag the SLAM might take a few days or longer and you need to consistently add LC. How’d the CYA jump up so fast? I’m assuming too short of a period between addition and testing lead to an over addition.

I maintain my CYA with an SWG at 80, but you might be better off dumping water to 70. With breaks between visits I’d want to target the top of recommended and 80 CYA makes top end above 10 FC, so it’s kind of a pain to dance that line and get accurate PH measurements.

I’m also wondering if maybe the volume calculation is off with Poolmath, might wanna try to reverse engineer the actual volume based on chemical additions unless you’re 100% confident.

 

[TxFireAg]

Might wanna pack a bag the SLAM might take a few days or longer and you need to consistently add LC. How’d the CYA jump up so fast? I’m assuming too short of a period between addition and testing lead to an over addition.

I maintain my CYA with an SWG at 80, but you might be better off dumping water to 70. With breaks between visits I’d want to target the top of recommended and 80 CYA makes top end above 10 FC, so it’s kind of a pain to dance that line and get accurate PH measurements.

I’m also wondering if maybe the volume calculation is off with Poolmath, might wanna try to reverse engineer the actual volume based on chemical additions unless you’re 100% confident.

luckily I’ve got a good month to work this out. I think I let the CYA get too low and the FC dipped and I wanted to reverse that and ended up adding too much conditioner too fast. I’ll get it down to 80 or so. PH is luckily trending in the right direction especially for a slam.

What I’m confused about is during SLAM they say FC ~40% CYA so thats 40 for me right now. After SLAM what’s an ideal FC to maintain if I keep CYA at say, 80?

 

[mknauss]

After SLAM what’s an ideal FC to maintain if I keep CYA at say, 80?

At or above 7.5% of CYA. See FC/CYA Levels

 

[SoCalTFP]

luckily I’ve got a good month to work this out. I think I let the CYA get too low and the FC dipped and I wanted to reverse that and ended up adding too much conditioner too fast. I’ll get it down to 80 or so. PH is luckily trending in the right direction especially for a slam.

What I’m confused about is during SLAM they say FC ~40% CYA so thats 40 for me right now. After SLAM what’s an ideal FC to maintain if I keep CYA at say, 80?

At 80 CY I believe target is 7-11 FC. I try to target 9.5 (I fiddle with my SWG daily) to keep it below 10 because above that can effect the PH test accuracy.

Since your going to have less frequent testing I’d want to maintain at the max. Which means you need to be at 70 CYA and 10 FC as your targets. Could just be me, but after my SLAM I wanted to stay as far away from the minimum as possible!

Also not sure how easy the drain will be to get CYA down but you might want to do that first. The lower your CYA the less LC you’ll need, maintaining 40 FC won’t be easy, probably 5 gallons added a day or more potentially/probably. If water is cheap I’d probably take it back down to 40-50 CYA and call it a rookie mistake. Clear the SLAM procedure then bring it back up to 70 and target 10 FC.

 

[TxFireAg]

At or above 7.5% of CYA. See FC/CYA Levels

Alright got the algae worked out and FC back down to 9 and CC at 0. Levels currently are:

FC 9.0
CC 0.0
pH 7.8
TA 110
CH 500
CYA 90
Salt 3300
Temp 86
CSI 0.34

Currently have the SWG on super chlorinate as I come out of SLAM and since we are swimming daily (except during SLAM.) I plan to back that down through the next 1-2 down and see what FC does. I snagged some liquid chlorine to raise my FC (only if needed) without bringing pH back up. My pH has been 8.2+ for months and I’m trying to lower it so I can aerate out the TA.