using citric acid to remove metal stains...

[river-wear]

I figured it was iron, but for the sake of curiosity, what color are copper stains? Green?

Here are the full test results for today:

Cl - zero again; added 1/2 gallon of 10% chlorine (sodium hypochlorite)
pH - 7.2
alk - 60
Cal - 220
CYA - 50
salt - 2800ppm per test kit (AutoPilot says 3600...)

What are the desired levels for alkalinity and calcium?

There's still a puck in the skimmer and the chlorine generator is doing its thing, so I didn't want to add too much more of the liquid. I'll check on it again tomorrow. The water is clear and blue, but it feels like I'm tempting fate by writing that.

I still have a few stubborn stains in one spot, but all of the little speckles have disappeared now. Is there something you'd recommend for spot-treating?

Thanks!

[BigRickysPool]

I have a Hayward CZ 250 heater and it has a flow/pressure switch which detects water flow. If I do not have water flowing through my heater, the heater will not ignite. I also put in two valves that control water flow to the heater and also used to bypass it. This is a good idea in the Spring as water usually needs to be balanced and has crud in the flow. Also, during the summer months, when you do not need the heater, there is no reason to have water running through your heater. Doing so just exposes the heat exchanger to possible damage if you run unbalance water through the heater for an extended period of time. The damage is usually due to the copper in this unit. Trust me. I have already replaced one heat exchanger and it was expensive. Two cheap valves can eliminate most of the risk.

[waterbear]

I figured it was iron, but for the sake of curiosity, what color are copper stains? Green?
Green, blue, black, grey, brown (copper color). Black and grey are the most common colors on fiberglass.
Here are the full test results for today:

Cl - zero again; added 1/2 gallon of 10% chlorine (sodium hypochlorite)
pH - 7.2 bring this up to 7.6 slowly once your stain treatment is finsihed and all stains are gone
alk - 60 bring it up to 70 ppm
Cal - 220 bring this up to 400
CYA - 50 bring this up to 80
salt - 2800ppm per test kit (AutoPilot says 3600...) What kind of test? I would tend to trust the Autopilot on this since that is what the cell is actually measuring. It's still withing the operational range so nothing to lose sleep over.

What are the desired levels for alkalinity and calcium?

There's still a puck in the skimmer and the chlorine generator is doing its thing, so I didn't want to add too much more of the liquid. I'll check on it again tomorrow. The water is clear and blue, but it feels like I'm tempting fate by writing that.

I still have a few stubborn stains in one spot, but all of the little speckles have disappeared now. Is there something you'd recommend for spot-treating?
Put some vitamin c tablets in an old white sock and hold them on the stains.
Thanks!

Hope this is helpful. The numbers I gave you above will have your water 'balanced' even if the pH drifts up to 8.0, which happens with SWGs so you should not have any bad scaling conditions. It is a bit aggressive at a pH of 7.2 but you want aggressive water when dealing with stains. At pH of 7.6 to 8.0 you are golden and that is where I would recommend you run the pool. Don't let the pH rise above 8.0 nor drop below 7.6 in normal operation and you will be golden.

[river-wear]

Thanks for the help, Evan. I'll doctor things up to get a better balance. Maybe I won't have to be adding acid quite as often if the water is buffered better. I do usually run the pool at a pH of 7.6. One question though - why so high on the CH?

You asked about the salt - I used one of PoolDoc's test kits for that. I think it's more accurate because when I was relying on the Autopilot last year (too lazy to test), the chlorine just didn't seem to keep up with demand and I had to put the SWCG on the highest power setting. Now, with the higher salt level I put it back down to the "normal" power setting (there are three) and the water has been clean & clear all summer. In any case, it's in operating range as you pointed out; it just seems to run better/more efficiently now. I also read that the Autopilot will read the salt levels with varying accuracy depending on the temperature of the water.

[waterbear]

Thanks for the help, Evan. I'll doctor things up to get a better balance. Maybe I won't have to be adding acid quite as often if the water is buffered better. I do usually run the pool at a pH of 7.6. One question though - why so high on the CH?
To keep the water balanced with the other parameters I gave you since you have a plaster/fiberglass pool. I kept your Saturation Index within 'range' with a pH range up to 8.0 so you don't develop scaling conditions and there is some evidence higher CH can help prevent fiberglass staining. The parameters I gave you for CYA, pH and TA are to minimize your acid demand.
You asked about the salt - I used one of PoolDoc's test kits for that. I think it's more accurate because when I was relying on the Autopilot last year (too lazy to test
I am going to assume this includes all tests including pH and CYA, correct?), the chlorine just didn't seem to keep up with demand (sounds like low CYA) and I had to put the SWCG on the highest power setting. Now, with the higher salt level I put it back down to the "normal" power setting (there are three) and the water has been clean & clear all summer.
Did you raise your CYA?
In any case, it's in operating range as you pointed out; it just seems to run better/more efficiently now. I also read that the Autopilot will read the salt levels with varying accuracy depending on the temperature of the water.

Understand that the Autopilot is meaureing conductivity and not chloride ions like a chemical test. While the two are usually in the ball park they are not the same and for the sake of a SWG operation it's interested in the conductivity of the water and nothing more.
(Poolsean, Please correct me if I am wrong on any of this)
As far as the PoolPilot power settings, these should have nothing to do with salt level UNLESS you are running your salt way too low or unless your cell is fouled with calcium deposits and needs cleaning and cannot generate enough chlorine. The salt sensor in the AutoPilot is temperature corrected, which is why your cell output seems to fluctuate somewhat with temperature. My question for you was where was your CYA when you had to run at the higher power level? Low CYA is more likely to cause needed to bump the power than any other reason. Evan now at 50 ppm your CYA is too low and you should raise it to 80 ppm. This will translate into lower output setting which will translate into less CO2 outgassing which translates into more stable pH. The lower TA is also to lessen the outgassing of CO2. Ditto for not allowing the pH below 7.6 in normal operation. The lower you put the pH the faster you outgas CO2 and the faster pH rises.

[river-wear]

Interesting stuff, thank you!

Today I picked up the baking soda for raising TA, and will get the CYA and calcium tomorrow.

No, I wasn't too lazy to test other things last year. I just skipped the salt test. Last year I ran the Autopilot with it reading 2800-3000ppm (now it's 20% higher).

My CYA is about the same as it was last year. I added some this spring because the pool overflowed with a bit with the winter rains, diluting it. That's why I had to add quite a lot of salt too. In any case, I will bring it up to the recommended levels.

[waterbear]

Be sure to only raise the TA by 10 ppm. You want to keep it at 70. (You could also just leave it at 60 ppm for now and if and when it drops below bring it back to 70 ppm and not higher! )
You have never said how big you pool is so I cannot help you with dosing info but for everh 1000 gallons a SCANT 1/4 cup of baking soda will be in the ballpark to raise the TA by 10 ppm.
I would put in 3/4 of the amount you need over a period of several days--a small amount each day (because you just did the stain removal and you don't want pH to jump quickly lest the stains return., wait 24 hours after the last addition, adjust pH to 7.6 if it is higher (use your acid demand test if you have one)--If it's lower don't worry too much about it, wait another day your TA.
If it it still too low start adding the remaining 1/4 of the baking soda left over a few days and repeat the pH adjustment and testing.

I would not do this until you have finished with all the stain removal and your chlorine is holding properly.

[river-wear]

Pool size is in my signature - 27,000 gallons.

I only put in a one pound box of baking soda so far. (The pool calculator site says I'll need five.) I had to add water last night and didn't want to bring up the pH too quickly, just like you wrote. I will hold off until I can get in there with the Vitamin C tablets to finish off my stubborn stains. (And get the chlorine stable.)

I'll look for calcium hypochlorite at the pool store (my once-annual trip, I suppose) to try to hit two birds with one stone. I realize that more calcium will be needed than just what is in chlorine though.