Low alk, tough to raise

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Seanboy

Active member
Nov 3, 2016
40
NC
Hi guys, I have a 27 round, above ground. Ran it crystal clear all summer until the wall failed late Aug (rust spot, older pool). Put in a new one, filled it and immediately had an algae problem, maybe I was to slow on the cya.. anyway looking to balance the numbers, but my tf100 showed me 20 alk, added an entire 5lb bag of sodium bicarbonate and only raised it to 30alk, shouldn’t 5lb for a roughly 17k gallon pool raise it much more?

I want to make sure I’m not crazy before continuing.

Thanks!

P.s. eastern NC and had tons and tons of rain, possible contributing factor to the low alk?
 
Seanboy said:
shouldn’t 5lb for a roughly 17k gallon pool raise it much more?
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If your TA testing is accurate and the pool is indeed about 17K. every 40 oz (2.5 lbs) should raise the TA by about 10 ppm. Rain water won't impact the TA unless you had significant overflow. Local water can influence the TA, but in most cases local fill water has a higher TA. You might test your fill water TA to be certain it's not exceptionally low and to also confirm your TA testing process..
 
What is the source of your fill water? Municipal or well?
 
This might be a clue: "and also purchase another alkalinity test to compare"
What are you using for testing? Pool stores, test strips, etc. have all proven over and over to be wildly unreliable and inaccurate....
 
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I’m using the TF100 test kit. Checked the hose water (municipal) alk is 30, tested from the filtered fridge water alk is 40. Is this abnormally low? Should I get another alk tester?
 
Seanboy said:
Is this abnormally low?
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That is some fairly low TA form your local water. But continue with the baking soda in 10 ppm stages. Get it up to at least 50 and you should be fine for a while.
 
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Seanboy said:
my tf100 showed me 20 alk, added an entire 5lb bag of sodium bicarbonate and only raised it to 30alk, shouldn’t 5lb for a roughly 17k gallon pool raise it much more?
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Sounds like @JamesW has the answer. Add another 2.5 lbs. Don't be surprised if it jumps from 30 to 50. PoolMath is a best approximation, and the testing has margins of error. So sneaking up on it is best.
 
Yes, the color becomes solid with no change. Maybe it’s not a huge deal, but just uncommon for such alkaline water from the source. I wanted to be sure before I continued with balancing the chemistry.
 
Seanboy said:
Maybe it’s not a huge deal, but just uncommon for such alkaline water from the source.
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Perhaps not the most common, but we do have pools from around the country that are supplied from a water source with an unusually low TA. Good thing is you have a proper test kit and can keep an eye on it. :goodjob:

One last TA tip from me though. The TA test has been known to be influenced by static electricity at the bottle tips. Usually this is with new bottles. So at some point you might consider having a damp cloth nearby and wipe the tips of the reagent bottles after every 2-3 drops just to ensure you are seeing nice, full droplets falling from the bottle as you are dispensing.
 
My tap water tests in the same ranges, so I tend to buy several big bags of baking soda each spring. I haven't worried too much about inconsistencies in results when going from fairly low levels to higher. I blame complexities in the actual pool chemistry, as well as assumptions in the math. As my additions get closer to the target, the accuracy forecast for amounts needed does improve.
 
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