Just switched from trichlor tabs to BBB

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poolslideblue

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Apr 8, 2013
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Moved into a house 2 years ago with a circa-1970s 40k gal plaster pool. We've been using trichlor tabs and shock for chlorination :roll:, adding shock and balancing pH based on hard-to-read test strips. The pH has been fairly stable for the past 1.5 yrs and we've been attempting to maintain 3-4 ppm FC based on the test strip manufacturer recommendations.

We'd been fighting mustard algae blooms every 1-2 months and couldn't figure out why as we'd been maintaining the recommended chlorine levels. Every 1-2 months required an expensive and pain staking regiment of 32 oz of Polyquat 60 + 32 oz of clarifier followed by a vacuum to waste of the dead algae.

I stumbled onto the BBB method section of this site a week ago and immediately ditched the trichlor and shock, switching to Clorox 8.25% bleach from Costco (until I stock up at the next bleach sale). Just received my TF100 test kit and recorded a pH of 7.8, FC of 4.5ppm, CC of 0-0.5ppm, and CYA of 110-120 ppm before I ran out of sunlight. Currently bringing the FC up to 9ppm per the Pool Calculator.

Will take TA and CH levels tomorrow. Looks like a 1/2-1/3 water replacement is in my future. Hope to have this old pool in check soon.

EDIT: Today's measurements
FC = 9 ppm
pH = 8.2
CYA = 110 ppm
TA = 130
CH = 470
 
You have a good understanding of what is needed. Depending on where you live, you may just want to hold high FC levels for the remainder of the season and allow the CYA to dilute down over the winter from rainfall.

If you have some more season left, drain/refill now may be your best path....allowing you to run much lower FC levels.

What does your water look like?
 
CYA doesn't evaporate so as water evaporates it actually concentrates and when you refill it goes back to where it was before. A lot of people drain water for winterizing and that also drains off some CYA so when they refil after winter the CYA is lower than before. If you don't close the pool then you don't have that as an option. In that case, draining now might be your best bet.
 
FC = 9 ppm
pH = 8.2
CYA = 110 ppm
TA = 130
CH = 470

Plaster pool with a hot tub and constantly aerating jets. Should I reduce TA by adding muriatic acid to bring pH down to 7.0-7.2, then aerate with the hot tub to bring it back up? Thinking step 1 should be drain and refill half the pool to bring down CYA, then worry about everything else.
 
I'd dilute the water to get the CYA down first. It's hard to fight algae using chlorine when the CYA is so high. After the CYA is lowered, then you can look at your other numbers and if the TA is high and your pH tends to rise, then you can lower the TA if you want.
 
Bama: Your statement above confuses me:
CYA doesn't evaporate so as water evaporates it actually concentrates and when you refill it goes back to where it was before.
Click to expand...

That implies that draining and refilling would also get CYA back to where it was previously. Draining water is different than evaporation? I'm guessing that means that evaporated water doesn't include CYA for some reason? Not questioning your knowledge; just trying to understand.

By the way, see you on September 14 in College Station. :wink:
 
Whenever water evaporates, the water leaves, but dissolved minerals and chemicals do not, leaving a more concentrated solution.

When draining, both the water and the minerals/chemicals leave together. The remaining water contains the same concentration as the original.

That's the difference between the two processes.
 

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