Pink slime!

[waterbear]

Here's the one thing that niggles at me. I don't mind keeping FC higher than where I've kept it -- around 3.0 -- except that Jandy's SWCH says that I can cause damage to pool metals by maintaining FC higher than 3.0. I don't know if there were talking specifically about the metals as part of the SWCG, or if that's their position for general water balancing. Since all my Jandy equip is under warranty, I'm hesitant to maintain FC higher than 3.0. Thoughts on that matter?

Thanks

Thoughts on the matter is that low pH is the main factor that can damage metals in a pool. High chlorine with stabilzier is not really high chorine. If you had and UNSTABILIZED pool then 3 ppm FC would be rather on the high side.

As far as your calcium, brin it up to 400 to 450 and drop your TA to about 70 ppm.

You might noit have noticed a faster pH rise when the pH is lower but the chemistry behind it supports it. The lower the pH the more bicarbonate (TA) is converted into carbonic acid (basically CO2 in water) and the operative word here is acid. The more CO2 in the water the faster it outgasses, particularly with a bit of aeration going on, either from your waterfall or from the hydrogen bubbles in the salt cell. Therefore by minimizing the on time of the salt cell (by running the CYA at the upper limit and also running the FC at a level appropriate for that CYA level) AND by lowering the TA to reduce the amount of bicarbonate in the water that can be converted into carbonic acid AND by limiting how low one drops the pH, once again to limit the amount of bicarbonate coverted into CO2 one effectively slows down the outgassing of CO2 and the associated pH rise. Many manufacturers don't understand the actual chemistry that is occurring and they attribute (incorrectly) the pH rise to the formation of sodium hydroxide in the water. Jandy is owned by Zodiac and I do not have a very high opinion of that company.

Jandy's recommended water balance levels are just the industry "standards" that manufacturers regurgitate to the public with no real understanding of water balance and they have changes quite a bit over the years. The FC should not be over 3 ppm is actually an outdated recommendation based on lack of understanding as to what CYA actually does (even though the CYA/Chlorine relationship has been known since the 70's and even published in books and articles. Nowadays, a general rule (and still incorrect) is that FC should never go below 2 ppm and should be up to about 4 ppm but this still does not work for CYA levels that are commonly found in pools running exclusively on trichlor or in salt pools.

[famousdavis]

Thanks waterbear. My TA tends to drop over time, so I can just not adjust it whenever it falls to 70, then. I'll hit the nearby pool store this weekend to pick up whatever it is that increases calcium. And I'll up my FC a little beyond 3, and see if the pink slime stays away (actually, it's already 6.0 because of when I hit the Boost button; I tamped down the SWCG % ontime just 10% following the Boost, so the FC would fall very slowly, which it has). I'll try keeping FC no less than 5% with the higher CYA level.

I looked over my pool records today. My pH rose 0.05 per day over the last 10 days, where the waterfall wasn't running, where I had my pool covered, and where the water temp was between 81 and 77. That's a slower pace than when my pool is uncovered and the waterfall is running; that's when I see up to a 0.1 rise per day (sometimes it's a little less than that, actually, but it's very close to 0.1).

This morning I uncovered the pool where the pink slime had been earlier; no pink slime visible from above the surface of the water. I'll uncover the pool this weekend and examine everything more closely to see what's going on.

Thanks again!

[famousdavis]

What's the difference between calcium chloride dihydrate and calcium chloride? Is one preferred over the other?

[waterbear]

What's the difference between calcium chloride dihydrate and calcium chloride? Is one preferred over the other?

Only difference is the amount needed to achieve the same rise in calcium hardness. The dihydrate has two water molecules attached to it so it weighs more so you need to add more. Whichever you can get is fine. I have found the dihydrate is more readily available and usually buy the Tetra brand in 50 lb bags. Dowflake and Peladow is usable but it does have a higher bromide content (although not as much as if you add a sodium bromide based mustard algae killer).

[famousdavis]

Nice plan waterbear!!!! :-)

Many thanks for not just your advice, but for your explanations on why you're giving your advice!

[famousdavis]

waterbear's Checklist:

"Raise the CYA to 80 ppm and run your FC between 4-5 ppm and you will be golden." (I added the last pound of stabilizer that I had, so the CYA is probably about 60 now; FC still running about 6.0, but it should fall since I'm running the SWCG less time now)
Drop the TA to 70 ppm (it's at 80 now; I'll just let it fall to 70 on its own over time)
Keep the CH between 400-450 (I boosted CH way up to just under 400 now. Will top off next weekend after I'm assured my CH addition yesterday is thoroughly mixed)
Keep the pH no lower than 7.6 and drop it when it hits 8.0 (it was at 7.4 Saturday, and is probably 7.6 today; I'll add less acid when it's time to adjust the pH downward)
Keep salt between 3000 and 3500 ppm (currently running 3.3 or 3.4 according to the SWCG; pool store co's said it's a bit lower than that reading)

I checked the SWCH plates and sensor yesterday -- first time ever since getting our pool last May! -- and the sensors were spotless, the plates had no build-up of any gunk that I could see. I'll check on that again since I'm running higher calcium now, to ensure the plates and sensor stay clean.

And there was no pink slime to be seen anywhere in the pool this weekend. Lookin' good!

[waterbear]

I checked the SWCH plates and sensor yesterday -- first time ever since getting our pool last May! -- and the sensors were spotless, the plates had no build-up of any gunk that I could see.
Of course they were since you have been running a negative CSI for a while and have aggressive water that will dissolve calcium.
I'll check on that again since I'm running higher calcium now, to ensure the plates and sensor stay clean.
They should. If you check the CSI range for the parameters I gave you will find that it ranges from about -.3 to about +.24 which is balanced water! (This is with the TA at 70 ppm. At 80 ppm the water will have a bit more tendency to scale so you might want to think about dropping the TA by 10 ppm since , if you are not overdosing on acid, your TA should stay fairly stable for a while.)
And there was no pink slime to be seen anywhere in the pool this weekend. Lookin' good!

Use you acid demand test to get an idea of how much acid to add. I measure the acid into a plastic measuring cup that I put on a plastic dinner tray. If any spills I jut push the whole tray into the pool. One you get used to how much acid your pool takes you can eyeball it pretty close but you really should measure at first. If you don't want to measure acid then get a gallon jug and fill it with water and measure that to get your eyeballing of the acid more accurate. It's just practice.

[waterbear]

Thanks waterbear. My TA tends to drop over time, so I can just not adjust it whenever it falls to 70, then.

That is because you have bee just dumping in acid and doopping the pH too low when you add it. When you add acid you lower both TA and pH but you lower TA MUCH SLOWER than pH. Another reason to not drop the pH as much...if you read the stickly on the procedure to lower TA is it to:
Drop the pH low (7.0 to 7.2) to lower TA AND pH
Aerate to raise pH without affecting TA by outgassing CO2
repeat until TA is where you want it.
AS I said before, the LOWER you drop the pH the MORE you outgas CO2 and the FASTER the pH rises. What I did not add to that is the FASTER the TA will drop!

If you only want to drop the pH from, say, 8.0 to 7.6 then use the acid demand test in your K-2006 and get an idea of how much acid is needed to lower the pH. I think you will find you have been overdosing on acid! Once you do that I think you will find that your TA is much more stable. It is normal for TA to drop over time but it should not need upward adjustment very often at all if you are not using an acidic chlorine source like trichlor. What is the TA of your fill water?

As far as your CYA and FC, remember this is a pool, not a science experiment. Keep it simple and don't lose sleep over it Raise the CYA to 80 ppm and run your FC between 4-5 ppm and you will be golden.
Drop the TA to 70 ppm
Keep the CH between 400-450
Keep the pH no lower than 7.6 and drop it when it hits 8.0
Keep salt between 3000 and 3500 ppm

If you do this your water will be balanced over a temperature range of about 70 to 90 degrees! Easy! (At water temps below about 75 degrees don't let the pH drop below about 7.8 if you lower pH but as long as it is below 8.0 I would not worry about it.)