PolyQuat and Shocking with Chlorine

[CarlD]

Richard,
You are the chemist, I'm just a rule-of-thumb, what-I've-observed guy.

It may be that my method has no more basis to it than wearing a tin-foil hat and throwing salt over my left shoulder--I don't know. But I've been successful with it for several years, and so have other folks.

There is a mechanism for why PolyQuat drops FC--CC doesn't seem to rise when it does that. PoolDoc (who seems to be VERY busy these days) probably has discussed it--I think he did.

I do know that PolyQuat is far better at INHIBITING algae growth than as an algae killer.

But our whole goal of winterizing is to keep the water clean and clear once the pump is off until the water is absolutely too cold for algae growth.

I've never noticed a problem with my filter filtering out PolyQuat but WaterMom has. She suggests running the filter on Recirculate for 24-48 hours after heavy dosing with PolyQuat. I find if I add it slowly to the return stream it distributes. It's a thick, oily liquid and needs to dissipate sufficiently so it can't be filtered out. Once it's fully distributed there definitely is no problem with it getting filtered out.

BTW, weekly dosing during the season of an ounce or two in the return stream doesn't require "recirculate"--it's the heavy dosing of a quart or two that may.

[chem geek]

Well I'm not a chemist by trade (I'm a color and imaging algorithm and S/W programming guy at work), but have an interest in pool water chemistry and remember enough chemistry (which was my major along with physics) to know some things, but not others. And it's through real-world observation that we really learn what goes on, regardless of "theory". So that's why I asked.

I found one post where Ben says that PolyQuat and high chlorine levels are incompatible, but nothing else explaining it. The fact that users see chlorine levels drop rather precipitously while the CC only goes up a relatively small amount probably means one of the following:

1) PolyQuat consumes (combines with) chlorine to perform some sort of chlorinated PolyQuat, but does not show up completely in the CC (TC) test.

2) High levels of chlorine oxidize PolyQuat (i.e. break it down) which would explain the large drop in FC while CC doesn't climb very much. If this is the case, then it doesn't make much sense to close the pool with PolyQuat. Perhaps it's OK to use PolyQuat first, at lower chlorine levels, and then later (perhaps a few days or a week later) shock the pool with chlorine. I did read that it is recommended not to shock the pool within 48 hours of using PolyQuat.

3) High levels of PolyQuat interfere with the FC test so that the chlorine level is still high but one does not know it from the test.

If I were a betting man, I'd bet that #2 is what is going on. And yes, I'd sure like to hear from Ben on this, but understand if he's too busy.

As for the black algae problem that keam (Kristi) has in her pool, after she hopefully gets rid of it (at least all visible signs of it), she should probably use a PolyQuat small maintenance dose on a regular basis or perhaps could use 50 ppm Borates to prevent further outbreaks without requiring the higher chlorine levels. It may be that with black algae that nothing will completely get rid of it (especially in plaster pools, though hers is vinyl) so the best one can do is keep it from growing.

The level of chlorine that she reported was the minimum needed to prevent regrowth of the black algae corresponded to a disinfecting chlorine level of 0.07 ppm which roughly corresponds to the Max. column in Ben's best guess CYA chart.

Richard

[Jakebear]

Since my pool is in limbo right now I can play and see what happens. I’m waiting for the temp to drop per Carl’s recommendation so I can close it. The FC is 5.0 right now with no algae.

I’ll add the recommended dose of PolyQuat 60 and let you know what things test at in the morning.

Edit: I forgot to mention -- the pool is completely covered with a mesh LoopLock cover ~ 90% shade, about 2 feet above water level.

[Jakebear]

Just checked FC down from 5.0 to 3.8ppm after 19 hours of circulating. Combined is .2ppm.

I used my Peristaltic Pump to inject the diluted Quat (1 gal h2o) into the return stream. That took about an hour since it only pumps 20gal/day

[Jakebear]

Another 30 hours have past and the Free Chlorine is down to 2.8 ppm and just a hint of CC (FAS-DPD barely pink) I'll call it .2 but if I could have used a half drop that probably would have done it. Also noticed pH is up a bit to 7.7 from 7.5 before the Quat.

I will begin injecting 6% Bleach when the pump come on (very early morning because of the frosty conditions). Anticipated (calculated) increase is 2.5 ppm based on injection rate and run time --- We'll see.

[CarlD]

Well, I just finished closing my pool today. I had my FC at 4, then added 48 oz of PolyQuat to my 19,200 gallon pool. FC dropped to 0. I then shocked it up, and, today, when I closed, FC was 13.5. I used Liquid Chlorine.

[haze_1956]

My understanding is that Polyquat is a essentially a Non-foaming Detergent.

I have read posts that recommend lowering chlorine levels before adding it when dealing with algae,

And some posts have recommended high chlorine to clear foaming in the pool.

So the question is, does chlorine break down detergents?
.

[chem geek]

Well, I just finished closing my pool today. I had my FC at 4, then added 48 oz of PolyQuat to my 19,200 gallon pool. FC dropped to 0. I then shocked it up, and, today, when I closed, FC was 13.5. I used Liquid Chlorine.

The 48 oz in 19,200 gallons is equivalent to 25 oz in 10,000 gallons so 2.5 times the example I calculated earlier. So I would expect this PolyQuat to consume 2.5 * 2.2 = 5.5 ppm of chlorine so it is not surprising that it consumed all of your 4 FC. In theory, it would have consumed another 1.5 ppm of the amount you added to shock, though you've said that you didn't notice this when you then added chlorine to shock level, though 1.5 might not be that noticeable when shocking to 13.5 (it's a 10% error).

[chem geek]

Also noticed pH is up a bit to 7.7 from 7.5 before the Quat.

If everyone is seeing a pH rise when the chlorine gets used up by the "full" amount we have been seeing (the 3:2 molar ratio), then this gives an interesting clue as to what may be going on. The process of producing a combined chlorine, as with a chloramine or a chlorinated organic, is a basic (alkaline) process. In the case of ammonia, one of the hydrogen gets replaced with chlorine and produces water. Since the weak acid (HOCl) is thus consumed, this is a slightly basic process. In the case of creating a chlorinated organic, the process would be similar if this were a nitrogen with hydrogen attached, but PolyQuat has methyl groups attached to each nitrogen. So, a possible scenario is to replace the methyl group with chlorine thus releasing methanol. This is again a weakly basic (alkaline) process.

Achieving breakpoint is an acidic process that is so strong that the net of the above formation of a chlorinated compound plus breakpoint is a slightly acidic process. However, this is for the simple process of breaking ammonia. I am not clear as to what exactly would happen in breaking PolyQuat.

What doesn't make complete sense is that a replacement of one of the methyl groups, analagous to producing a monochloramine, would have the chlorine used up in a 1:1 molar ratio while if both methyl groups were replaced, analagous to producing a dichloramine, then the chlorine would get used up in a 2:1 molar ratio. Yet we are seeing a 3:2 molar ratio that is normally associated with achieving breakpoint of ammonia. Very strange indeed...

Richard

[Jakebear]

The fact that users see chlorine levels drop rather precipitously while the CC only goes up a relatively small amount probably means one of the following:

1) PolyQuat consumes (combines with) chlorine to perform some sort of chlorinated PolyQuat, but does not show up completely in the CC (TC) test.

2) High levels of chlorine oxidize PolyQuat (i.e. break it down) which would explain the large drop in FC while CC doesn't climb very much. If this is the case, then it doesn't make much sense to close the pool with PolyQuat. Perhaps it's OK to use PolyQuat first, at lower chlorine levels, and then later (perhaps a few days or a week later) shock the pool with chlorine. I did read that it is recommended not to shock the pool within 48 hours of using PolyQuat.

3) High levels of PolyQuat interfere with the FC test so that the chlorine level is still high but one does not know it from the test.

If I were a betting man, I'd bet that #2 is what is going on.

Richard

So where do we go from here? I started with 5.0ppm FC and within 48 hours I was down to 2.8ppm. The PolyQuat dose was a start-up dose (Clean Pool) of 1oz per 1000 gal H2O. The question is since the Chlorine went down and has been restored ---- is there any Quat left??

Is there a way to test to see if there is PolyQuat remaining? At $75.00 per gallon for 60% PolyQuat, it would be nice to know what’s happening.