Quickly rising pH and high CC after installing SWCG

[Exlonghorn]

I recently installed a SWCG, and it's doing a good job of maintaining FC levels, however I am seeing a faster rise in pH now. pH rose to 8, so I added muriatic acid to drop it back to 7.6. About a week later it's back at 8 again. I am only running the VS pump at 1750rpm for 7 hours a day, so I didn't expect to get much rise due to aeration, but this appears to be a thing now. Before adding the SWCG and VS pump, I ran the SS pump full speed about 5 hours a day and didn't see this issue with pH rising so quickly...I only had to add acid once over the summer. I just added muriatic again to get it back down to 7.4 and now I am considering adding borates to buffer the pH through the winter (Houston, so the pool stays open so I can use the spa). I also recently saw my CC increase to 2,0, which I haven't seen ever since I started following TFP methods in the spring. CYA is 75. It's been raining and leaves are dropping so that's a contributing factor (and I empty the leaves from my robot every few days) So I am working two problems at once, but I think the sequence/priority matters. The plan is to:

1. Address the CC problem first by doing a SLAM.
2. Once I bring the FC levels back down under 10ppm, move the pH to 7.4 and then add borates to buffer the pH rise going forward.

Anything else I should be considering?

 

[ajw22]

Rising pH seems to be a byproduct of a SWG. Let your TA get down to 50-60 before adding borates. SWG pool like running at pH around 7.8. Lowering the pH to 7.4 will just give a more rapid rise.

A few things looking at your PM logs:

-Your CYA is 80 if the dot disappears between 80 and 70 lines. You can't eyeball 75 as halfway between the lines since the scale is logarithmic, not linear. We always round up.
- How do you get a TA of 75?
- Why is your salt at 2000 if you have a SWG running. SWG's need salt at around 3000. Your SWG may not get giving you the CL output you expect at that salt level.
- Did you really have salt at 7000 on the 10/20 test?

Do a Overnight Chlorine Loss Test before you start the SLAM Process

 

[Exlonghorn]

Rising pH seems to be a byproduct of a SWG. Let your TA get down to 50-60 before adding borates. SWG pool like running at pH around 7.8. Lowering the pH to 7.4 will just give a more rapid rise.

A few things looking at your PM logs:

-Your CYA is 80 if the dot disappears between 80 and 70 lines. You can't eyeball 75 as halfway between the lines since the scale is logarithmic, not linear. We always round up.
- How do you get a TA of 75?
- Why is your salt at 2000 if you have a SWG running. SWG's need salt at around 3000. Your SWG may not get giving you the CL output you expect at that salt level.
- Did you really have salt at 7000 on the 10/20 test?

Do a Overnight Chlorine Loss Test before you start the SLAM Process

Just ran the TA and it’s a solid 70. I’ll shift the CYA to 80. Regarding the Salt, I just tossed a number in there because I didn’t believe the first test after the SWCG was installed. Just ran it again...7,700. That largely aligns with the first test you mentioned. Either I am doing the Taylor test incorrectly, or the installer added too much salt, but I am surprised that only adding 8 bags of salt put the number that high.

 

[ajw22]

I think you have a testing problem.

Are you using a 10ML sample with the K-1766 salt test?

 

[ajw22]

I am surprised that only adding 8 bags of salt put the number that high.

PoolMath says 320 lbs of salt will raise 22,000 gallons by 1,738 ppm.

 

[Exlonghorn]

I think you have a testing problem. The IC60 will give you the HIGH SALT light if over 4,500.

Are you using a 10ML sample with the K-1766 salt test?

I have a TruClear, which is not equipped with a high salt warning.
I used the 25ml sample with the SpeedStir and the Taylor SampleSizer.

 

[ajw22]

You use 10ml with the K-1766.

Test Kit Instructions and Tips

Swimming Pool Test Kit

tftestkits.net

Taylor K-1766 Salt Test Kit instructions


Salt Water Test Instructions
PROCEDURE: CAREFULLY READ AND FOLLOW PRECAUTIONS ON REAGENT LABELS. KEEP REAGENTS AWAY FROM CHILDREN.
For 1 drop = 200 ppm Sodium Chloride.

1. Rinse and fill the plain graduated cylinder to 10 mL mark with water to be tested.
2. Add 1 drop R-0630 Chromate Indicator. Swirl to mix. Sample should turn yellow.
3. Add R-0718 Silver Nitrate Reagent dropwise, swirling and counting after each drop, until color changes from yellow to a milky salmon (brick) red. Always hold bottle in vertical position. NOTE: Do not add enough R-0718 Silver Nitrate Reagent to give a brown color. First change from yellow to a milky salmon (brick) red is the endpoint.
4. Multiply drops of R-0718 Silver Nitrate Reagent by 200. Record as parts per million (ppm) salt as sodium chloride (salt water).

 

[Exlonghorn]

You use 10ml with the K-1766.

Test Kit Instructions and Tips

Swimming Pool Test Kit

tftestkits.net

Taylor K-1766 Salt Test Kit instructions


Salt Water Test Instructions
PROCEDURE: CAREFULLY READ AND FOLLOW PRECAUTIONS ON REAGENT LABELS. KEEP REAGENTS AWAY FROM CHILDREN.
For 1 drop = 200 ppm Sodium Chloride.

1. Rinse and fill the plain graduated cylinder to 10 mL mark with water to be tested.
2. Add 1 drop R-0630 Chromate Indicator. Swirl to mix. Sample should turn yellow.
3. Add R-0718 Silver Nitrate Reagent dropwise, swirling and counting after each drop, until color changes from yellow to a milky salmon (brick) red. Always hold bottle in vertical position. NOTE: Do not add enough R-0718 Silver Nitrate Reagent to give a brown color. First change from yellow to a milky salmon (brick) red is the endpoint.
4. Multiply drops of R-0718 Silver Nitrate Reagent by 200. Record as parts per million (ppm) salt as sodium chloride (salt water).

I am an idiot. Lol. Corrected test is 3000ppm.

 

[ajw22]

I am an idiot. Lol.

You are not the first making the 25ml mistake.

 

[Bvacchiano]

I’m down here in Sugarland and I can tell u PH will always rise with the SWG. I keep my TA at 70 and it still rises and I don’t run my waterfalls very often. I do run the Spillway for the spa twice a day but that’s necessary. Anyways are u running your water features daily? Right now with the water temps cooler my ph doesn’t rise as quickly.
I keep my PH between 7.6-8. I do so because to keep my CSI in range that’s what it requires. Also if i drop TA any lower it will also affect my CSI negatively. I would imagine you will be in same boat.

 

[Exlonghorn]

I’m down here in Sugarland and I can tell u PH will always rise with the SWG. I keep my TA at 70 and it still rises and I don’t run my waterfalls very often. I do run the Spillway for the spa twice a day but that’s necessary. Anyways are u running your water features daily? Right now with the water temps cooler my ph doesn’t rise as quickly.
I keep my PH between 7.6-8. I do so because to keep my CSI in range that’s what it requires. Also if i drop TA any lower it will also affect my CSI negatively. I would imagine you will be in same boat.

I'm aligned with your numbers. This is the test from this afternoon. I just dropped my pH, but it'll rise of course. I'm running my VS pump at low speed about 7 hours per day. It does go over the spillway between the spa and pool, but it doesn't "waterfall", so the aeration is minimized. No fountains, waterfalls, or other features. I've added borates today, so I'll be curious to see how well that performs as a pH buffer.

 

[setsailsoon]

I switched to swg about 6 months ago. My pool had been in liquid chlorine service for prior 5 years and consumed MA every week to keep in the recommended range except when I used trichlor tablets when I was traveling. After switching to swg and borate my pool is consuming about the same amount of total MA/week. I believe a lot of folks convert to salt from using tablets. Tablets are half CYA which is acidic and often eliminates the need for MA. When you switch to swg you have to now add acid.

Don't know if this explains rising pH for everyone but it's definitely what happened in my case.

I hope this helps.

Chris

 

[Exlonghorn]

Okay, looks like things are settled...hit the target for Borates while keeping TA, pH, and CH on target. I will monitor pH for the next several days and see if it keeps showing a rapid rise now that I have an effective level of borates in the mix. I am curious to see how well it really buffers pH. I'd like to keep pH at 7.8, which will get the CSI around -0.26. With water temps so low it'll be tough to get the CSI much better. BTW, PoolMath is simply awesome. I don't know how people can keep their pools straight without it.

 

[aussieta]

you are aware that ph reads false high when fc is above 10
so it appears you are aiming too low on your ph
i would aim higher for your ph which will also help your csi
and let that ta number drop, even down to 50

 

[Exlonghorn]

you are aware that ph reads false high when fc is above 10
so it appears you are aiming too low on your ph
i would aim higher for your ph which will also help your csi
and let that ta number drop, even down to 50

Indeed I am aware...I've been letting the FC drift down for the past week and will continue to let it drift down until it gets to the 6-7 range and then dial in a sustaining dose with the SWCG. I just cut the chlorinating % to 25% to speed up that process. I'll keep checking the pH along the way to see if it noticeably shifts once I get back under 10. If it drifts up like it has been, it'll work itself right up to 7.8-8.0.

On dropping the TA, I plugged 50 into PoolMath and with the other levels remaining unchanged it is giving me a -0.820 CSI. That seems like a bad idea?

 

[aussieta]

my numbers
fc 8.5
ph 7.8
ta 50
ch 450
borate 50
salt 3000
cya 60
csi -0.47
so you can fudge the ph and ch a little higher and let ta drop a little
i add acid maybe 2-3 times per year, maybe a quart total for the year
i let it rise to close to 8 and then drop to 7.8

 

[Exlonghorn]

my numbers
fc 8.5
ph 7.8
ta 50
ch 450
borate 50
salt 3000
cya 60
csi -0.47
so you can fudge the ph and ch a little higher and let ta drop a little
i add acid maybe 2-3 times per year, maybe a quart total for the year
i let it rise to close to 8 and then drop to 7.8

Okay, -0.47 is outside the recommended range of 0 to -0.30, but I know there is another standard that says to keep your CSI between 0.60 and -0.60 for plaster pools. I would need to do a significant drain and refill to move the CYA from 80 to 60. I'm also guessing your water temp is about 10 degrees F warmer than mine, so that also explains the difference. With keeping the CYA at 80, dropping the TA to 50 is a bad move. I could increase the CH to get closer to your number and that might help a bit. I am following the guidelines provided here...
https://www.troublefreepool.com/blog/2019/01/18/water-balance-for-swgs/

If I leave all my parameters the same, but nudge the pH to 7.8 and plan for the water temp getting to 78°F between May and September, the CSI ends up at -0.10 during the summer months and -0.25 during the winter months (average 62°F). That's pretty solid. Hopefully I won't need to mess with the pH too much once the FC is back under 10. I'll be very happy if I get the same pH results as you with only adding acid periodically. If the pH keeps rising quickly, I'll lower the TA to 70 and see if that helps. Lowering TA to 60 seems to quickly push the CSI out of range (-0.53 at 62°F), so 70 sounds like a good compromise.

 

[aussieta]

during winter i dont touch my ph and let it go to 8 if it wants to, to offset the lower temperature

 

[Exlonghorn]

Last log for this thread. After installing a SWCG and experiencing quickly escalating pH levels, I added borates to 40ppm and waited for the FC levels to come back under 10ppm. Today the FC hit 9.5 and the pH had been solid at 7.7 for over a week. The borate addition seems to have done the job as intended. And yes the water appears more refractive as well. It’s taken a couple weeks to get through the whole process, but I am very happy with where this ended up. The chlorine generator works terrifically and I’d recommend one to anyone using liquid chlorine.

 

[setsailsoon]

uh oh... you've crossed to the other side!