Does MA contribute to increasing pH issues?

stlcard87

Member
Jun 9, 2010
17
Hey guys, got a quick question for you/ in need of some suggestions to my issue.

First off this is not a private personal pool, its commercial full size with a heavy bather load. An easy 200+ people per day. Outdoors during summer months, and covered in winter with a pressurized dome. Thus im seeking the help from you experienced pool guys who have possibly worked around this type scenario.

Ill post my problem first then stats.

I have been battling a constantly high pH for about a month now. No issues whatsoever this summer. Our Sanitizer, - Cal Hypo Tabs un-stablized- is fully automated. As well as our pH system which is acid only. Our sensor/computer/ and acid lines are running fine and normal thus i think its water chemistry issue.

The pH has been on average 7.8 for some time. Last night we added an additional 4 gallons(based off poolcalculator.com) of muriatic %31.45 to drop the pH to 7.45 (normal level for us). oddly enough it didnt work.

We have the beginning signs of a Mustard Algae bloom on our slope. Could this be the cause of our pH issue? Does Algae raise pH?

I know how to treat the MA, and after typing this out i suppose itll be best to treat the algae issue first, then see if there is still a pH issue. Lastly, will this high pH cause trouble for my MA treatment?

We will soon be closed for about a week to install our "bubble" over the pool for winter, so nows the best time to hit these issues. Any tips you guys have with MA or possible culprits for my high pH will help greatly.

Stats: 360,000 gal
FC- 4ppm
pH- 7.8 average
Alk- 100 (slightly above our normal 80)
CH- 310
CYA- 42
Temp- 82-84 F

I plan to hit the MA with roughly 100# Cal -Hypo Shock and 12# nuclo Yellow Shock and clear which has worked miracles on MA in the past.

Should i try to drop this pH before i treat the MA?
 

frustratedpoolmom

TFP Expert
LifeTime Supporter
In The Industry
May 20, 2007
12,177
SWSuburban Chicago, IL
Yes - lower the PH first - is it possible that the acid you used is weaker than thought?
Why use the 12# nuclo Yellow shock (and what's in it?-active ingredient wise? - probably unnecessary is why I'm asking...)
Also what strength cal-hypo? it may be enough to reach shock level once - but maybe not to maintain it?
 

bk406

Well-known member
Dec 3, 2009
2,690
Central Massachusetts
frustratedpoolmom said:
Yes - lower the PH first - is it possible that the acid you used is weaker than thought?
Why use the 12# nuclo Yellow shock (and what's in it?-active ingredient wise? - probably unnecessary is why I'm asking...)
Also what strength cal-hypo? it may be enough to reach shock level once - but maybe not to maintain it?

hey stranger!!
 

chem geek

TFP Expert
LifeTime Supporter
Mar 28, 2007
12,082
San Rafael, CA USA
NuClo Yellow Shock has this MSDS indicating that this is sodium bromide which will essentially turn your pool into a bromine pool so you don't want to overdo this and it's not technically necessary unless you don't want to shock with an FC that is 60% of the CYA level (around 25 ppm FC for your 42 ppm CYA). The instructions usually have you lower the pH to 7.2 (verify this on the package). You would NOT shock to high chlorine levels while doing this treatment -- if you want to shock with chlorine, do that first and then when the chlorine level drops lower then you can add the NuClo Yellow Shock if you really want to do that (normally you do one or the other, not both).

The algae is unlikely to be the cause of your higher pH. The higher TA (100 vs. 80) is much more likely to be the cause. Along with the presumably higher aeration due to the higher bather load, the pH will tend to rise. In fact, even at 80 ppm, with the aeration in this pool you'll likely have pH rise.

Was the FC always at around 4 ppm with the 42 ppm CYA (are you sure this CYA number is right -- have you verified it with your own CYA turbidity test)? If a pool gets infested with yellow/mustard algae, then it can take an FC level roughly 15% of the CYA level to keep it in check (so 6 ppm in your case), but usually you want to kill it off completely if you can, get behind light niches and under removable ladders, put in pool cleaning equipment into the pool when shocking, etc. However, with a large commercial/public pool, odds are someone is going to reintroduce this algae by swimming in a lake and not cleaning their swimsuits with warm/hot soapy water.

Since you are using Cal-Hypo, how are you keeping the Calcium Hardness (CH) in check? Are you doing significant water dilution?

At 200 people per day then if they were in the pool for an hour over the day on average that would be 1800 gallons per bather which is a high-medium bather load (where < 1000 gal/bather-hour/day is high; 1000-5000 is medium; >5000 is low). So do you have any sort of supplemental oxidation system (UV, ozone, non-chlorine shock, enzymes) for the pool? If not, you might consider that to lower disinfection by-products, especially when the pool becomes an indoor pool in the winter.
 

stlcard87

Member
Jun 9, 2010
17
first off thanks for the tips. I have treated our past algae issues with either a shock treatment or the nuclo technique i did not mean to imply we dump both at the same time. =P

We will probably shock first with our granular Cal-Hypo 65%. Then if unsuccessful try the nuclo treatment we've used before. The Nuclo treatment does call for a chlorine shock treatment combined with itself. If i remember correctly its roughly 1.5 - 2#'s of shock per 15,000 gal. ( i may be off with this ill have to check the directions obviously before i go dumping #'s in. haha)

"Was the FC always at around 4 ppm with the 42 ppm CYA (are you sure this CYA number is right -- have you verified it with your own CYA turbidity test)?"

- Yes our FC is balanced to our current CYA level. Im guessing a lifeguard mis judged our Taylor droplet test and recorded an inaccurate ppm. Ive checked it since, and we are balanced.

- Our hardness usually stays in check through our constant need to backwash our system to waste. Our filtration system is somewhat out-dated and in my own opinion not capable of handling the bather load we have. Its 9 sand filter's each w/ roughly 7.5 sq footage size. Which is awful to deal with seeing as the plumbing is somewhat of an ancient nightmare with 9 multiports to deal with per each backwash. But with our constant backwash to waste and combined addition of new fresh water we are able to maintain our hardness in the 260-340 ish range.

Likewise I would love a UV system but budgets and other costs at our club tend to keep that a distant dream. We do use non-chlorine shocks and enzyme treatments to make sure our water quality is safe and sparkling year round. With the exception of our occasional algae blooms =P

thankyou all for the tips you are a great help to the pool community commercial and res!
 

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