? Benefit of Borate Level of 15-20? in SWG Pool?

[aehaas]

I have a 32,000 gal PebbleTech plaster pool here in Florida. It has around 80% sun exposure through the day. The area is screen enclosed. Pool usage is Zero, an expensive decoration. It has a built in hot tub section with a waterfall into the pool with around a foot drop. The aeration from that is what I would call minimal. The pool was resurfaced about 4 years ago with the “colored pebble stones" for “looks”.

Issue No. 1:
I have been getting an occasional green algae wisp at the waterline in a shaded area. It clears after superchlorinating with 2.5 gal of commercial liquid pool chlorine (?12%) and an extra dose of poly algicide along with brushing. This occurs on the average every 3 weeks during the summer. The chlorine level is around 8 - 10 when measured several hours after adding the super chlorine. What are the best options to reduce this algae from forming? The water is always clear.

Issue No. 2:
I add around a gallon and a half of 31.5% HCl a week to keep the pH around 7.1 - 7.5. I like it a little lower to maximize the effectiveness of the chlorine. This seems as too much work. I am looking for better buffering.

Baseline readings:
I test the water with: Industrial Test Systems: Pool eXact® EZ Photometer, Part No. 486201. I’m a biochemist among other things so accuracy matters...
SWG: CircuPool 45 running at 60% now. It runs 10 hours, 9AM-7PM.
Usual Readings:
Water Temp: around 83F now

Free Cl 3.0-5.0
TA-115
CH-240
CYA-40 (I like it a little lower to have better free Cl levels)
Cu-0.08, Phos-Nil, Fe-not routinely tested.
NaCl-3550
TDS-3900
EC-7.2 mS/cm
pH varies 7.0-7.6 but I try to keep it around 7.1-7.2
LSI- (-)0.25

A few times I had more significant algae streaks at more locations. The generator was clogged and needed to be cleaned. The Cl was found to be as low as 1 or 2 at those times, free chlorine. It seems like that level should be enough though. I only brush the sides of the pool maybe once a month but certainly if there is a little algae showing. I have an electric pool vacuum cleaner ?Dolphin? brand - use it once every other month or less often.

So I have added #28lbs of Borax (and appropriate acid) to the pool to get it up to around ?15 or so. It should help with the buffering and possibly keep that little bit of algae from forming. Do I really need to add 2 to 3 times more Borax to a level of 30-50?

Ali

 

[YippeeSkippy]

Hello! Welcome to TFP

I'll try to answer your questions succinctly- Your FC is often too low and it allows algae to repeatedly grow. Your occasional treatments with a gallon of liquid chlorine may slow it down some, but unless you maintain that blast of chlorine until all algae is dead, it will just reappear. For the record algaecide isn't a great algae killer. Its more useful in helping prevent algae. Hopefully you aren't using copper containing algaecide either or that introduces its own problems. Brushing weekly will also go a long way in helping too. You need to do a SLAM process to rid your pool of algae once and for all--SLAM Process

You're spinning your wheels trying to keep your pH that low while your TA is 115 (assuming that's accurate). Apparently its ineffective at improving your chlorine's actions also since you are still getting algae.

Since your pool is under the screen, your CYA doesn't have to be as high as someone whose pool is more exposed. The screen diminishes some of the UV rays.

Do you keep your tester well calibrated? Do you have a way to test for CCs (combined chloramines)? You need to.

TDS means nothing- just all the "chemical bits" in your pool "solution".

Your FC should be based on your CYA level- Here's a reference guide for ya-->FC/CYA Levels

We don't recommend the addition of Borates to any pool that is still having wide swings in pH. Once you add them it will be more difficult to adjust your pH.

You should pay attention (via PoolMath, either the app or the classic web version at the bottom) to your CSI to avoid aggressive water which can be damaging to your plaster.

Your copper level is not good- copper containing algaecides?? Got any stains from copper?

Maddie

 

[YippeeSkippy]

This might help you understand why we go with CSI instead of LSI-

Pool Water Chemistry

This thread presents my findings so far on pool water chemistry including the following: More Accurate Calcite Saturation Index (CSI) to replace Langelier Saturation Index (LSI) Calculation of ppm HOCl (disinfecting chlorine) at various levels of Total Free Chlorine (FC) and Cyanuric Acid (CYA)...

www.troublefreepool.com

 

[ajw22]

This might help you understand why we go with CSI instead of LSI-

Pool Water Chemistry

This thread presents my findings so far on pool water chemistry including the following: More Accurate Calcite Saturation Index (CSI) to replace Langelier Saturation Index (LSI) Calculation of ppm HOCl (disinfecting chlorine) at various levels of Total Free Chlorine (FC) and Cyanuric Acid (CYA)...

www.troublefreepool.com

This is a summary of that thread...

CSI and LSI - Further Reading

www.troublefreepool.com

 

[aehaas]

I actually read these threads, each several times. I learned a lot. The chemistry was enlightening. I can see that I need a higher level of free Cl to truly rid the pool of lingering algae, SLAM. I will do it.

"Your copper level is not good- copper containing algaecides?? Got any stains from copper?"
I have not used Cu containing algicides. I do have a heater that I occasionally run for a short time just to be sure it works. That is where the copper is certainly originating. But is a level of 0.08 really high? Do I need to chelate to remove it? I have no stains.

Again, do you think a Borate level of 15 gives me some algicide activity? I can tell you that my pool does seem better buffered now. I did investigate CSI vs LSI and found that the LSI and CSI numbers were about the same for my pool chemical levels.

AEHaas

 

[ajw22]

Again, do you think a Borate level of 15 gives me some algicide activity? I can tell you that my pool does seem better buffered now.

Are Borates an Algaecide?

While Borates tend to have a minimal effect as an algaecide one shouldn’t utilize them to prevent algae. The boron concentration that that is required to noticeably reduce the risk of algae is far higher than what is generally considered safe so we generally don’t utilize them to prevent algae, we only focus on the benefits for buffering pH changes.

 

[aehaas]

Let me thank you all for your help!

ali