Pink slime!

[CarlD]

First off, I think, using an SWCG, your levels are probably incorrect. SWCG usually call for a CYA of 60-90 ppm, generally 80ppm. At any level FC should be 5% or more of the CYA. But I've not heard of an SWCG system that recommended a CYA level that low. Second, you have both what I think is an algae problem and a low grade CC problem. The cure for both is to shock your pool to at least 15ppm and maybe 20.

We don't say don't shock your pool. We say don't shock your pool if it's not necessary, but definitely do when it is. And I think it is now.

You did not mention your pH. Higher pH makes the water less irritating but makes chlorine less effective. If your pH is running at 7.8 or higher, I think you need to lower it. If it "trends" high, then you should lower your TA as well. I KNOW higher levels are recommended but that's not always right. This past summer I ran TA at 60 and almost NEVER had to adjust pH, which stayed between 7.5 and 7.6.

CH levels are recommended for hard pools between 200 and 400ppm. But if you're getting grout loss at 250, you may need it higher. Not sure what you can fill the spaces with underwater except underwater epoxy, but as for looking nice....Someone else will have to advise you.

Carl

[famousdavis]

Thanks for your reply, CarlD.

My SWCG levels are correct. Jandy recommends CYA levels between 50 and 75 (higher if pool temps are 85 degrees or more, which my pool is not). Since my average FC level is 3.0, that's a little more than 5% of the CYA level, so I should be good on that account. But since my CYA level was at the low end of the recommended range, I added more CYA as you suggested.

I don't think I've got an algae problem because my CC levels are never higher than 0.5, and often 0.0 (more a factor of how I test the water, I think). My FC levels move only very slightly overnight. And, I add a weekly dose of polyquat 60 just to stave off any algae problems. I think the pink slime (bacteria) just happens to tolerate my pool's conditions as they currently are. I think your advice is still sound, though, so I used the "Boost" mode on the SWCG which raises FC about 12ppm over 24 hours.

I did forget to mention my pH level! I keep it between 7.2 and 7.8 (Jandy's recommended range again). On the day it hits 7.8, I add acid to bring it back down to about 7.2 or 7.4. My pool's pH rises 0.1 daily on average, so I add acid about every 6 days or so.

And it's not so much that I'm losing the tile grout because of water conditions, it's just that the pool builder guy doing the trowel work with the tiles didn't happen to do a good job filling in the space between these few tiles on one end of the swim out. I'm not seeing any issues with the pool except that one place on the swim out.

So, in short, I added CYA, boosted the chlorine, and will continue to just monitor things. I may try the underwater epoxy assuming it comes in some sort of shade of white. Hopefully the shocked pool will kill off the pink slime bacteria for now, and I'll keep on top of my son so he regularly brushes down the pool walls and floor on a weekly basis.

[waterbear]

Bottom line is this, if you got pink slime your chlorine was NOT high enough. To kill it shock the pool to the shock+ range in the best guess chart.

When shocking it is better to add bleach or liquid chlorine instead of the boost function. One main reasons is that you want the high FC level immediately and not over the course of 24-48 hours. A second one is the boost function does shorten cell life.


As far as the CYA goes, higher CYA indirectly leads to better pH stability because it directly translates into less cell on time which translates into less formation of hydrogen bubbles which translates into less aeration of the water which translates into less outgassing of CO2 (which is the main cause of pH rise in a salt pool), which translates into slower pH rise.
On the same note, the lower you put the pH the faster it will rise so you will get better pH stability for a longer period if you do not lower the pH below about 7.6 and only add acid when it rises above 7.8. (easy to do using your test kit's acid demand test).

Your waterfall is a source of aeration also and is contributing to pH rise so you mgiht benefit by lowering the TA to about 70 ppm or even 60 ppm and raising the CH to still keep the water balanced. (around 450 ppm will keep your water balance at a pH range of 7.6 to 8.0).

Finally, you might want to consider adding borate to 50 ppm for it's many benefits, including better pH stability and it's algaestatic action.


Your CYA should be around 75 or even 80, particularly since you are located in Florida (so am I) and you should run the FC at 4-5 ppm. You should not need to be adding polyquat at all with a SWCG that is operating properlysince chlorine levels will stay pretty constant. Also, polyquat does cause a temporary lowering of the FC in the pool.

(Carl, while it is true that higher pH does make chlorine less active IN AN UNSTABILIZED POOL it changes once CYA is added to the mix and the effect of pH on a stabilized pool, while still present, is minimal.)

As far as the grout problems, it is definitely a water balance issue. Your calcium is way too low and most likely, when you added acid to drop the pH (which you said often went down to 7.2 or 7.4), your calcium saturation index dropped low enough on the negative side to make the water aggressive to plaster and grout. For example, given the water parameters you listed and a temperature of 80 degrees for the water ( not uncommon in Florida) your CSI would be about -.7 which is definitely aggressive!

[famousdavis]

Hi waterbear - thanks for your reply.

Yes, bottom line is, you're right, my cholorine was not high enough to keep pink slime away. And I knew that the preferred way to shock is to do as you suggest -- use liquid chlorine -- but I didn't have any and I was going out the door to work, so it was easier to hit Boost. That's not something I'd regularly want to do, though.

I did add more CYA -- not a lot -- so I'll see what it's like the next time I test for CYA or the next time I go to the nearby pool store.

My experience confirms what you said about the waterfall. When I'm running it, my pH rises about 0.1 per day. When I'm not running it, pH rises more slowly. I haven't detected, however, a similar bouncing effect by bringing my pH down to 7.2 after I add acid. pH seems to rise at the same rate irrespective of whether I bring it down to 7.6, 7.4 or 7.2 (I don't measure acid, so the lowering of pH tends to vary).

My grout issue isn't a water balance issue -- at least in the spot I've had trouble with. The problem existed after the pool was built in that one area of the swim-out. By the time I noticed it, the pool was full, and the too little grout wasn't a concern to me...except it seems to make it nice for pink slime to grow there. That said, I'm not familiar with CSI measurement, so if I'm subjecting my pool to the possibility of aggressive water as I try balancing my water, I'll need to do up my game a bit there. Based upon what you've said, it seems like upping my CH to maybe over 300 would be a good idea (Jandy recommends between 150-400, I think). Your thoughts on the optimum CH level for my pool?

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

[famousdavis]

I went to the Pool Calculator website, entered my numbers in. Seems like if I have pH at 7.2, I'm over the threshold of safety (not making any adjustments). Seems clear that just adding some extra calcium would be a good idea here:

pH = 7.2
TA = 80
CH = 250
CYA = 50
Salt = 3300
Borate = 0
Temp = 80
CSI = -0.68

pH = 7.3
TA = 80
CH = 250
CYA = 50
Salt = 3300
Borate = 0
Temp = 80
CSI = -0.58

That said, my pH spends most of its time above 7.2 or 7.3 -- more like 7.6 or 7.7. So in that case, I wouldn't need to do anything:

pH = 7.6
TA = 80
CH = 250
CYA = 50
Salt = 3300
Borate = 0
Temp = 80
CSI = -0.3

Maybe if I just go easy on the acid addition -- something you suggested doing anyway -- I'd be okay here.

[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]

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.)