PH Consistently 8+ in a Small Gunite Michigan Indoor Pool

[drdamour]

Hi,

i bought a house a few years ago with a 5000 gallon indoor inground gunite pool. As long as i've been testing it, the PH consistently gets up to 8+. I use dry acid to slowly move it down to the "ideal" 7.2-7.6 range, this usually takes 2-5 applications over 7-10 days. For a week or two it will stay in the ideal range, but after a week or so it's back to 8.

It's driving me crazy as i've been told the higher PH means the cholorine is clumping and dissipating faster (my chlorine levels go to nill during this proces). I'm not sure if this is even true.

After i get the PH down and the chlorine right, i will occasionally add an algae fighter, but this doesn't seem to affect the pattern in any way.

I'm totally lost and need some help, i'm happy to provide any information i can (brands, amounts, a well documented scenario) i just want this to not be a problem. In fact i'm not even sure it's a problem, but it's been explained to me that the low chlorine lets algae grow which is a problem, although there is no visible algae in my pool as far as i can tell. The water is very clear, and the walls are very blueish-white. Should i test for algae in some way?

Just let me know what i info i need to provide, or things i need to try, i want to learn to do this the right way. Are you just supposed to add acid to your pool every week? that doesn't seem right, especially in an indoor pool.

One final note, in the past it didn't even matter if no one swam in the pool, the PH would rise regardless of it's occupants.

[PoolDoc]

I can't give you a definitive answer, based on the information you provided, but I can tell you that the chlorine "clumping together" explanation is bogus. PH levels may affect chlorine consumption, though I've never been able to verify that personally, from either experience or publication. However, if they do, the effect is not dramatic, and does not involve "clumping".

Several things do effect pH, including aeration (via carbonic acid / CO2 off-gassing), plaster erosion (which can have to do with how the plaster was applied) , and salt water chlorine generators (SWCG). Also, use of bleach or calcium hypochlorite does tend to cause a pH rise. In particular, cal hypo use -- if you follow label directions -- can have significant effect.

Finally, if you are using test strips, your testing may be more the issue than the strips.

Several things you need to know:
#1 - Long term use of dry acid (sodium bisulfate), without draining, can lead to sulfate build-up and (reportedly) plaster and concrete corrosion.
#2 - Most algaecides consume chlorine and if your pool is truly indoors, you don't need them.

Here's what I would recommend:
#1 - Tell us what sort of pump / filter / pool surface / enclosure you have, along with what chemicals and maintenance routine you are using.
#2 - Get a Taylor K2006 or 2006C testkit (Amazon links in my signature) and report results. If your pool is genuinely indoors (no UV) you can substitute a K2005 (use the link provided, and the search for "Taylor K2005", or go to lesliespools.com) and save $10 - $20 at the cost of less flexible and less accurate chlorine testing.
#3 - Tell us how you use the pool (average daily use, etc.)
#4 - Tell us when it was last drained and refilled.

Best wishes,

[drdamour]

if you are using test strips, your testing may be more the issue than the strips.

I am not using strips i am using the liquid tests using phenol red, etc

#2 - Most algaecides consume chlorine and if your pool is truly indoors, you don't need them.

I've never heard that about me not needing it because of it being indoors. I had some greenish buildup on the steps of the pool and was told it was algae, and it seemed to go away when i used the algaecide.

Tell us what sort of pump / filter / pool surface / enclosure you have, along with what chemicals and maintenance routine you are using.

it's 3/4 HP Pump
the filter is cartridge is this one http://www.amerimerc.com/Pleatco-fil...0UM150tC=1.htm
For pool surface, i'm guessing you mean the walls? i've been told they're gunite, looks like white concrete like with any in ground pool. Is there someway i can tell?
for enclosure, i'm guessing you mean the room it's in? It's a room in my house, the indside walls are covered with t-111 siding. There's 2 doorwalls to the house and two doorwalls to the outside. There's two skylights.
I don't really have a maintenance routine because the ph keeps going so high. Once i get the ph balanced, i shock it with powder shock (i don't have name handly, i'll follow up) and put in a chlorene tablet in the dispenser thing. I test the levels every other day (generally in the morning) and after a week or two, the ph is back high, and i start the annoying cycle again.

Get a Taylor K2006 or 2006C testkit (Amazon links in my signature) and report results. If your pool is genuinely indoors (no UV) you can substitute a K2005 (use the link provided, and the search for "Taylor K2005", or go to lesliespools.com) and save $10 - $20 at the cost of less flexible and less accurate chlorine testing.

I ordered it, doesn't look much different from what i already have. Currently the chlorine level seems to be 0, the PH is currently 7.8, i just did an alkalinity test and it came back at 40 so i just added this morning 2 lbs of sodium bicarbonate, the package said this would double the count for my pool size (5k gallons). Reading through the intro/faqs here, apparently alkalinity could be a possible cause of my problems.

Tell us how you use the pool (average daily use, etc.)

We don't use it very often because of the balance problems. I'd say we use it every few days once it gets in balance, but after a week or two it gets out of balance and it seems to take a week to get the ph back.

Tell us when it was last drained and refilled.

In january of 2011

[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