PH Consistently 8+ in a Small Gunite Michigan Indoor Pool

[PoolDoc]

OK.

For now, add 1/4 gallon of plain 6% household bleach (all those adjectives matter!) which should add about 3 ppm of chlorine.

Get a gallon of muriatic acid (Lowes, hardware, etc.), and add about 1/8 gallon. Guess at the dosage; do not try to pour it out and measure it! Use glasses & gloves, and rinse away any splatters promptly. The fumes are a problem: avoid them by partially submerging the bottle in the water and pouring with the lip of the bottle only a few inches above the pool surface. Do NOT store the acid indoors; even tiny amounts of fumes leaking out can damage wiring!!

Once you have the kit, please take complete readings (FC, CC, pH, TA, CH, & CYA) and report them.

Regarding alkalinity, don't try to raise it, till you have pH, and hardness results as WELL as TA (total alkalinity) results.

Your low alkalinity + high pH suggest that it's worth looking for a source of aeration on your pool. Aeration strips the carbonic acid / CO2 from a pool shifting the carbonate alkalinity lower and the pH higher. A fountain, a water fall, a suction leak adding bubbles to the pool could all be the source of the problem.

Ben / PoolDoc

[drdamour]

Regarding alkalinity, don't try to raise it, till you have pH, and hardness results as WELL as TA (total alkalinity) results.

darn, too late, i did it this morning, does this alter your recommendations?
IS there an order to adding the chlorine and acid? do they need to be done 24 hours apart or anything?
Can you fill me in on the math behind the amounts you've suggested?

[PoolDoc]

Put bleach in the skimmer and acid in your pool, and you can do them both at the same time WITH THE PUMP RUNNING!

Chlorine math: 120,000 gal = ~ 1,000,000# water; 120/5 = pool factor of 24; 6% bleach => 8.6# x 0.06 = ~0.5 lbs Cl2 equiv; 24 x 0.5 = 12 ppm; 12/4 (1/4 gal) = 3 ppm

Acid math: seat of the pants. pH calcs are hard, even if you have accurate TA values, accurate knowledge of the various buffers present (polyprotic acids) and accurate initial pH values. Conservative seat of the pants measurements work OK.

Adding sodium bicarb now just means more acid later.

[CarlD]

Ben,
We haven't seen a CYA result. I know CYA should not be used in indoor pools, but drdamour put in some sort of powdered chlorine. If it wasn't cal-hypo....there's now a CYA presence...

More Chlorine Math:
FC desired (in ppm) = (1,000,000/pool gallons) * (.06) * num gallons. Since your pool is 5,000 gallons, and you want an FC increase of 3ppm, that's 1/4 gallon. .06 is the concentration of 6% bleach (6%=.06)
I can do THAT in my head since I know that 1 gallon of 6% adds 6ppm to 10,000 gallons. Since you have half that, 1/2 gallon gets the same 6ppm increase. Since you only want half of 6ppm, that's 1/4 gallon=1 quart of bleach.

Carl