Successful treatment of "pink algae"

[waterbear]

It is NOT more effecient at oxidizing organics. Monochloramine is a less potent oxidixer than hypochlorous acid. What happens is twofold. First and formost, monchloramine is a nitrogen containing compound and as such is a primary food for algae and many bacteria. It is actaully consumed as such and the "attached" chlorine kills the algae or bacteria from within. The second thing that happens is that the ammonia competes with the cyanuric acid in the water for the chorine and in this way 'deactivates' some of the CYA temporarily so the chlorine becomes more 'active' or effective at killing the algae or bacteria. This is also why sodium bromide becomes very effective since it essentially take the CYA out of the loop, so to speak since the chlorinated isocyanurates, which are the primary form of chlorine in a pool with high cyanuric acid levels readily oxidize the bromide ions to hypobromous acid which is much more potent than the clorinated isocyanurates.
These types of products are much more effective when the cyanuric acid levels in the pool are high and not as effective when they are in more normal ranges. Also, these types of bacterial growth do not occur in chlorine pools when the cyanuric acid levels are normal since more of the chlorine exists in the form of hypochlorous acid and not as chlorinated isocyanurates. Remember that monochloramine IS a chloramine and is not considered to be a desirable form of chlorine in the pool and is, in fact, one of the combined chlorinamines that we test for and eliminate by shocking the pool. Why? Because they are NOT as effective sanitizers or oxidizers as hypochlorous acid BUT when there is a high level of cyanuric acid in the water there is a very low level of hypochlorous acid. Most of the chlorine is in the form of chlorinated isocyanurates unless additional hypochlorous acid well over what is normally needed is introduced to move the equalibrium point of the reaction. (In other words, if your CYA is high you need to run MUCH higher FC levels and shock to much higher levels to have the same activity that you would have with CYA in the 30-50 ppm range and FC in the 3-5 ppm range.

As to why this occured in the third year of using trichlor the reason is simple and had NOTHING to do with your solar cover. Using stabilized chlorine causes the CYA to rise over time and the pool becomes overstabilized. I am interested at what your CYA level actually is. Would you post a full set of test results? Also, what kind of filter do you have. I believe in another thread you said a DE filter but is it a 'bump' flter or a backwashing filter? Remember that it got higher as each year passed and that third year is when it reached 'critical mass' and you developed the pink slime. This is a very common symptom of overstabilizd pools, btw.

As far as a more in depth discussion of the chemistry involved, the place to have that would be in the 'china shop' section of the forum since it really is beyond the scope of what the forum Administrator (Pooldoc) wants discussed in the general areas of the forum. You might want to review some of the info in the forum (and possibly some of the info over at Troublefreepool.com) about the chlorine/cya relationship and it's effects on pool chemistry. A good place to start is Pooldoc's sticky on his 'best guess chart' on chlorine levels for different levels of CYA that was posted by Watermom, one of the mods here.
http://www.poolforum.com/pf2/showthread.php?t=365

You can also search here or at Troublefreepool for posts by chemgeek. He has posted quite a bit of the theorectical chemistry on the chlorine/cya relationship.

[Water_man]

Thank you, Evan, for this detailed post. I’ve never seen anything more comprehensive on this topic before. The only thing that you missed are chemical equilibrium and kinetics constants of the reactions involved (just kidding…)

I inherited this pool from the previous owner of this property, which I bought three years ago.
BTW, I chose Water_man as my user name for a reason. I spend a LOT of time in the pool, to a degree that I’ve told my friends that I didn’t buy a house with a pool – I bought a pool with a house…

The pool is 28 years old, and to the best of my knowledge it has never had pink algae, although I’ve been using it in the last three seasons more than the previous owner has ever done for 25 years....
Since the pool is in New England, it’s open during early June through September.

I opened the pool on this Friday. Here are the numbers of the water analysis, done by the store’s colorimeter:

FC 0.22
TC 0.56
pH 7.9
CH 171
TA 101
CYA 56
Cu 0.22
Fe 0.38

You may be right about the CYA level and the possible ineffectiveness of my previous superchlorinations. I used to shock with 2 bags of calcium hypo, yielding 10 ppm FC, while "The Table"
shows that 20 ppm is the desired level.

My DE filter is a backwash type filter (Anthony Apollo VA 38 – 38 SF area) and I BW it frequently as needed (either when the pressure rises by 8 , or at least once a season.)

My pool opened as a swamp. Here’s why:
We had a lot of rain this winter and although I drained my pool upon winterizing about two feet, it got refilled during winter and the winter cover (mesh type) touched the water. I didn’t anticipate the unavoidable results of the combination of leaves and tree debris on top and the contact with my pool water, although the winterizing algaecide should have done its job. Next closing I’ll be smarter – I’ll have the submersed pumps in the pool ready in place, and one I notice the cover submerged I’ll pump out.

As to the green pool: I already shocked with bleach to a 20 ppm level and now the filter is working its a** off to clear the water. The green is gone. All I have is brown precipitate of dead algae, and bluish looking water with high turbidity. But I’ve done my reading here and elsewhere and I’m not panicky. I wonder if any “filtering aids” should help.

Last but not the least. I’d like to show my appreciation to the owner of the site and to make a donation.
Is this is commonly practiced and accepted, or, should it be better to subscribe to the sister site?
Regards,
Mike

[waterbear]

Thank you, Evan, for this detailed post. I’ve never seen anything more comprehensive on this topic before. The only thing that you missed are chemical equilibrium and kinetics constants of the reactions involved (just kidding…)

I save that kind of stuff for the 'china shop' section of the fourm

[mbar]

One other thing you can try is a "skimmer sock" It goes in the skimmer and collects the very fine particles. You can find them on the internet, or at some pool stores. You can also cut a pair of pantyhose and tie it off and put it over the skimmer basket. As for donating to this site - you used to be able to, but I don't think you can anymore. There is an owner of the site, but he has been missing from here for a while. The good moderators have kept up the site using all of their knowledge to help We all appreciate them so much Just keep posting and the good people here will help you with any question you have. Welcome to the forum.

[Water_man]

One other thing you can try is a "skimmer sock" It goes in the skimmer and collects the very fine particles. You can find them on the internet, or at some pool stores. You can also cut a pair of pantyhose and tie it off and put it over the skimmer basket. As for donating to this site - you used to be able to, but I don't think you can anymore. There is an owner of the site, but he has been missing from here for a while. The good moderators have kept up the site using all of their knowledge to help We all appreciate them so much Just keep posting and the good people here will help you with any question you have. Welcome to the forum.

Skimmer sock : another great idea I learned about in this forum.
My previous dying pump almost choked on it, but my new pump is unaffetcted. I'm amazed by the amount of fine particles it blocks. Cleaning it every few days by a garden hose is easy and it's worth the smal effort.

[traceyb]

Will it hurt to close the pool for the season if you haven't fully rid of the "pink" bacterium? I'm trying to shock the crap out of the pool after scrubbing and vacuuming it down, what else can I add to help kill this stuff? I was hoping to close in 3 days?????? Help?

[aylad]

If you don't kill all of the "pink" bacterium, it'll still be waiting for you when you reopen in the spring, and likely make your water worse as well because any chlorine you put in to winterize will just be used up fighting the pink stuff. Can you please post a set of current numbers taken with a drop-based kit, so maybe we can help you get it accomplished quicker?

Jante