SWG low chlorine + high pH

[CGNY]

I have been practicing TFP Pool Math for years, including using Twenty Mule Team Borax. It could be my imagination but this season my pool seems to be suffering from constant low chlorine along with high pH. I know that the process of creating chlorine via electrolysis creates Sodium Hydroxide which has a high pH.

So here is my question: When a salt water generator starts to go bad is it possible that it generates a small amount of chlorine while at the same time generating a disproportionally large amount of Sodium Hydroxide? or is there a direct correlation between the amount of chlorine and amount of Sodium Hydroxide generated? Additional info: I have no water features that could be driving pH up.

 

[mknauss]

I know that the process of creating chlorine via electrolysis creates Sodium Hydroxide which has a high pH.

Not true. The complete process is pH neutral.

Are you using more fill water this year? What is the TA of the fill water?

 

[pjt]

Twenty Mule Team Borax

How much are you adding and why? Can you post a complete set of test results from a quality test kit?

constant low chlorine

How are you testing? Have you performed a OCLT? How long are you running your pump? What's your SWG output %?

40k Gallon Pool and Spa | Jandy AquaPure PLC1400

You have a 40k pool and a SWG rated for 40k. You would benefit from a higher output SWG. At 100% output and running nonstop, your SWG will increase your FC by 3.7 every day, which may not be enough. You may need to supplement with LC.

 

[CGNY]

Not true. The complete process is pH neutral.

Are you using more fill water this year? What is the TA of the fill water?

mknauss: Thanks so much for your response. I am not using more fill water this year. I have an electric pool cover so evaporation is minimum. Fill water TA is 40.

 

[mknauss]

Great. So why do you use Borax? It raises pH.

 

[CGNY]

How much are you adding and why? Can you post a complete set of test results from a quality test kit?


How are you testing? Have you performed a OCLT? How long are you running your pump? What's your SWG output %?


You have a 40k pool and a SWG rated for 40k. You would benefit from a higher output SWG. At 100% output and running nonstop, your SWG will increase your FC by 3.7 every day, which may not be enough. You may need to supplement with LC.

pjt, Thanks so much for your response.

• I usually add 112lbs of Borax in the beginning of each season as my experience has been that it keeps pH from bouncing.
• Latest results: pH 8.0, FC 2, CC 0, CH 320, CYA 25, Temp 88, Salt 3,000.
• Test kit is Taylor K-2006C.
• DPD Powder + regent to test chlorine.
• I have not performed an OCLT but I will. Pool has a cover so I can do it any time of day / night.
• Pumps are running 5 hours a day on weekdays and 7 hours a day on weekends. SWG % varies as I increase to as much as 100% when chlorine is low and back off to as low as 10% when chlorine is at a good level. When pool is open I keep at 100% since CYA is on the low end. Also worth noting, this season, pool cover has spent more time than usual in the closed position with SWG % at 20% or so.
• I just changed the gallons in my signature from 40k to 32k to reflect a more accurate number. 40k was an old estimate, I have since tracked the gallons used on several seasonal full refills and amount is roughly 32k. This is my 12th season with the pool, same SWG model used every year, 2nd season with this actual SWG.
• Additional info- my pool has always consumed what I consider a lot of acid each year to keep pH at right level, however this year the chlorine and pH seem to no longer correlate with each other. Hence my post.

 

[Bperry]

pjt, Thanks so much for your response.

• I usually add 112lbs of Borax in the beginning of each season as my experience has been that it keeps pH from bouncing.
• Latest results: pH 8.0, FC 2, CC 0, CH 320, CYA 25, Temp 88, Salt 3,000.
• Test kit is Taylor K-2006C.
• DPD Powder + regent to test chlorine.
• I have not performed an OCLT but I will. Pool has a cover so I can do it any time of day / night.
• Pumps are running 5 hours a day on weekdays and 7 hours a day on weekends. SWG % varies as I increase to as much as 100% when chlorine is low and back off to as low as 10% when chlorine is at a good level. When pool is open I keep at 100% since CYA is on the low end. Also worth noting, this season, pool cover has spent more time than usual in the closed position with SWG % at 20% or so.
• I just changed the gallons in my signature from 40k to 32k to reflect a more accurate number. 40k was an old estimate, I have since tracked the gallons used on several seasonal full refills and amount is roughly 32k. This is my 12th season with the pool, same SWG model used every year, 2nd season with this actual SWG.
• Additional info- my pool has always consumed what I consider a lot of acid each year to keep pH at right level, however this year the chlorine and pH seem to no longer correlate with each other. Hence my post.

Are you tracking the borate level with all that borax?

 

[reggiehammond]

Have you had a good look at your SWCG plates for scale? Cleaned filter recently and certain you have normal, good flow across SWCG?

You describe some pretty violent SWCG percentage changes; from almost 100% to as low as 10%. I’d recommend backing off on changing frequently. Get the FC at target or higher, then let the SWCG for a week or two, tracking daily FC (same time of day.)

CYA could also come up to protect some of the generated FC. Even with a solar cover, you should consider raising to 40.

 

[pjt]

I usually add 112lbs of Borax in the beginning of each season as my experience has been that it keeps pH from bouncing.

Borax isn't required, it's an optional enhancement. You've been adding lots of borates to your water. Do you know your current borates level? What do you mean by pH "bouncing"?

Latest results: pH 8.0, FC 2, CC 0, CH 320, CYA 25, Temp 88, Salt 3,000.

What's your TA?

• Test kit is Taylor K-2006C.
• DPD Powder + regent to test chlorine.

Excellent.

Pumps are running 5 hours a day on weekdays and 7 hours a day on weekends. SWG % varies as I increase to as much as 100% when chlorine is low and back off to as low as 10% when chlorine is at a good level. When pool is open I keep at 100% since CYA is on the low end. Also worth noting, this season, pool cover has spent more time than usual in the closed position with SWG % at 20% or so.

That's not enough to generate the FC you need. Even though you have a cover, I'd recommend adding some CYA. Maintain your FC at or above the target FC for your CYA level: Chlorine / CYA Chart

Try setting a consistent pump run time and SWG %. Make small adjustments.