According to ChemGeeks spreadsheet my water is balanced with these numbers

[ubalr1]

I know my chlorine is too low for my CYA level. We plan a drain and refill in the fall. And, no more Bioguard after that! Here are my latest numbers (measured myself :) with a Taylor K-2006):

FC 3.0
CC 1.2
pH 7.1
Alk 140
Adj Alk 87.2
CH 990 :eek: (boy this was a pain, but it did change colors at 99 drops)
CYA 220 :eek:
water temp 87

Langelier Saturation Index (LSI) 0.12
Calcite Saturation Index (CSI) 0.02

Not perfect (0), but in the range, and the water looks great.

I've been trying to get the pH up with Borax but it doesn't seem to budge. If the balance is okay can I just let the pH ride at 7.1-7.2?

[duraleigh]

I'd leave the pH and Alk alone.....7.1 is fine if that's where your pool wants to be.

The CC of 1.2 indicates a need to shock...probably around 30+ppm to be effective.

And, as you already have acknowledged, you are DESPERATE for a drain and refill to manage the CYA and Alk. About two 60%'s will be needed to get your pool manageable.

I'm pretty sure how the CYA got there.....how did your CH get so high?

[ubalr1]

I'd leave the pH and Alk alone.....7.1 is fine if that's where your pool wants to be.

The CC of 1.2 indicates a need to shock...probably around 30+ppm to be effective.

And, as you already have acknowledged, you are DESPERATE for a drain and refill to manage the CYA and Alk. About two 60%'s will be needed to get your pool manageable.

I'm pretty sure how the CYA got there.....how did your CH get so high?

The fill water is very hard here (19 grains or 325 ppm if I got the conversion correct). That, and using calcium hypo for a chlorinating source I suppose. We drained the pool back in Feb04 and refilled with 50% soft water and 50% hard water. I am planning to connect the fill line to my water softener. I think it will be easier to monitor CH that way and add calcium as required. We have cartridge filtration (no backwashing) so the only water we lose is through evaporation. But here in Tucson that can be substantial I suspect. I'm guessing the cycle is - lose water through evap, then continually refill (auto refill) with very hard water.

What does two 60%'s mean? We have no problems completely draining our pools here in Tucson, so I could do a 100% drain.

[chem geek]

ubalr1,

As you point out, your chlorine level is too low for your CYA and that is certainly something to deal with immediately.

Don't worry too much about trying to hit the CSI to a perfect 0. This has a LOT of leeway, much more than I show in the spreadsheet. There are some users who don't see cloudiness until they get to +1.0 -- others around +0.75. Not sure about the corrosion side, but I suspect it's similar. So my spreadsheet "red values" that start at +/- 0.3 are VERY conservative, before I got some real-world experience from users on this site. Basically, the general rule on this forum is not to use LSI at all and just be in the ballpark (unless you don't have grout/plaster/gunite in which case CH is not needed).

At any rate, your numbers will all change after a drain and refill to get your CYA down since that will lower most of your other numbers as well (except CH due to its high value from fill water). You could probably run with a very low alkalinity of around 50 which would balance nicely with your high CH and let you run closer to a pH of 7.5. You will also experience less pH rise since your water will be less carbonated at a TA of 50 (though that doesn't seem to be a problem for you right now).

In the meantime, you can try using Ben's Lowering Your Alkalinity (http://www.poolforum.com/pf2/showthread.php?t=191) post to get your TA lower. With a lower TA you will be able to move your pH more easily. In fact, I am a bit surprised that you aren't already seeing a rise in pH from outgassing carbon dioxide. Are you using a pool cover? You could accelerate the process by aerating (splashing, pointing jets up, etc.) -- following Ben's procedure by going even lower in pH first should have this process go even faster. You aren't in serious danger with 7.1-7.2 pH if you just want to let it slowly drift upward, but aerating should accelerate that.

By the way, have you measured the CH and TA of your fill water? It seems quite high so would be good to know what you're dealing with when you do a drain and refill.

Richard

[duraleigh]

What does two 60%'s mean? We have no problems completely draining our pools here in Tucson, so I could do a 100% drain.
Many folks are reluctant to completely drain even a gunite pool, so draining 60% of the pool twice is sometimes easier and a nice, buffered way to keep chemistry in balance throughout the process.

[ubalr1]

ubalr1,

As you point out, your chlorine level is too low for your CYA and that is certainly something to deal with immediately.

Don't worry too much about trying to hit the CSI to a perfect 0. This has a LOT of leeway, much more than I show in the spreadsheet. There are some users who don't see cloudiness until they get to +1.0 -- others around +0.75. Not sure about the corrosion side, but I suspect it's similar. So my spreadsheet "red values" that start at +/- 0.3 are VERY conservative, before I got some real-world experience from users on this site. Basically, the general rule on this forum is not to use LSI at all and just be in the ballpark (unless you don't have grout/plaster/gunite in which case CH is not needed).

At any rate, your numbers will all change after a drain and refill to get your CYA down since that will lower most of your other numbers as well (except CH due to its high value from fill water). You could probably run with a very low alkalinity of around 50 which would balance nicely with your high CH and let you run closer to a pH of 7.5. You will also experience less pH rise since your water will be less carbonated at a TA of 50 (though that doesn't seem to be a problem for you right now). When I do the refill, it will be with softened water (CH=0). The autofill will also be replumbed to the soft water system too. I don't think I will have the calcium problem after the refill.

In the meantime, you can try using Ben's Lowering Your Alkalinity (http://www.poolforum.com/pf2/showthread.php?t=191) post to get your TA lower. Well, according to Ben's FAQs on Alkilinity, Alk should be between 50 and 200.

"What should my TA be?
Somewhere between 50 and 200 ppm. If you've got a heater, it usually should be lower than 150 ppm. If you've got a plaster or concrete based pool, it usually should be higher than 80 ppm."

Both my measured Alk (140) and adjusted Alk (87.2) fall within that range. I guess what matters is what the Alk is after I do the drain and refill.

With a lower TA you will be able to move your pH more easily. In fact, I am a bit surprised that you aren't already seeing a rise in pH from outgassing carbon dioxide. Are you using a pool cover? You could accelerate the process by aerating (splashing, pointing jets up, etc.) -- following Ben's procedure by going even lower in pH first should have this process go even faster. You aren't in serious danger with 7.1-7.2 pH if you just want to let it slowly drift upward, but aerating should accelerate that.

By the way, have you measured the CH and TA of your fill water? It seems quite high so would be good to know what you're dealing with when you do a drain and refill.

Richard

Here are my fill water numbers:

CH 160 (I guess my conversion from grains of hardness to ppm is wrong in my original post)
Alk 145

Thanks for all the feedback.

[ubalr1]

Many folks are reluctant to completely drain even a gunite pool, so draining 60% of the pool twice is sometimes easier and a nice, buffered way to keep chemistry in balance throughout the process.

A single drain of 95-100% saves me 4000 to 5000 gallons of water. A valuable resource here in the desert. I can see the benefits to both methods though.

[chem geek]

OK, now that your CH number is more "normal", at least for your fill water, it is true that you don't need to go as low in TA (the 50 I mentioned). 80 should be fine and yes, some people run with more but you then run the risk of fighting rising pH, especially if you have water features or other sources of aeration. So if your final CH in your pool is around 300 and your TA gets to 80-100 you are in very good shape indeed, but don't worry about this combination being perfect (i.e. CSI=0) since it does not have to be.

As for doing a full refill in a safe way that doesn't have your pool crack from underground water table pressure, some people have found that they can use a large plastic pool cover that extends way beyond the edges of the pool (a very large plastic sheet, actually, not a solar cover). Then with this on top of the pool, they simultaneously drain the water from under the cover while filling with water on top of the cover. This way, you can replace as much water as you want without ever having a lower water level and doing this efficiently to use the least amount of water possible. Really neat and I wish I could remember who said it or where the post was since I'd love to give credit where credit is due (I just love clever ideas). You could probably use a solar cover for this technique, though there will be some mixing at the edges (hopefully not too much).

By the way, how in the heck did you ever get your pool water's CH to 990? Did you add tons of calcium chloride pellets at some point?

Richard

[ubalr1]

By the way, how in the heck did you ever get your pool water's CH to 990? Did you add tons of calcium chloride pellets at some point?

Richard

I wish I knew for sure how it got so high. I suppose the test could be in error. I followed the Taylor instructions to the "T". To avoid false readings (due to fading endpoint) I added five drops of titrant (hardness reagent) to the sample first and then continued the test as usual. At 99 drops the sample finally turned blue. Next time I check it I'll follow the procedure for high CH (smaller sample, less drops, multiply by 25).