PolyQuat and Shocking with Chlorine

[chem geek]

Carl,

You mentioned in this post (http://www.poolforum.com/pf2/showthread.php?p=39765#post=39765) how large quantities of polyquat consume large quantities of chlorine (or vice versa) and others have reported the same sort of thing when they close their pools using high doses of both polyquat and chlorine.

I'd like to try and figure out what's going on so that we aren't doing something stupid. If you or anyone plans to close their pool this season with high doses of polyquat and chlorine and notice the chlorine (FC) level drop considerably, check on the combined chlorine (CC) level (by measuring total chlorine, TC) to see if it has gone up.

If the chlorine combines with PolyQuat to form a chlorinated PolyQuat, this should show up as a combined chlorine and perhaps it continues to be effective as an algicide in this form. However, eventually, it may break down (get oxidized) and not show up in CC and not be effective.

Just wondering if we are fooling ourselves thinking that we can close a pool with high chlorine and PolyQuat levels simultaneously. The fact that it is recommended that PolyQuat be added on a regular basis may mean that it gets broken down, though slowly under normal chlorine levels. Or it may mean that manufacturers just want us to use more and don't care about buildup (ya think!).

Richard

[jojasc]

This sounds like the scenario I am seeing.

I dosed my pool yesterday morning with polyquat after having had it consistently at 20ppm of CL for teh several days preceding. At the time I added the polyquat the FC was at 11.5, CC at 0.5. Tonight the FC has dropped to 6.0 while the CC remains at 0.5.

Should I raise the TC level back up to shock level now in order to close?

I also asked in the fall prep forum at what pint is there no longer a danger of filtering out the polyquat by changing multiport back to filter?

thanks,
John

[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 (http://www.poolforum.com/pf2/showthread.php?t=6139)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?
.

[CarlD]

I don't know about the last--or the first.

PolyQuat should NOT be used when fighting algae. By then it's too late and you must maintain consistently high shock levels of chlorine to do the job.

Since the only algaecide I use is PolyQuat, I never have had a foaming issue.

I know it sounds crazy to say this, but the simpler you go with your pool chemistry, ie, B-B-B, and the more relentless you are about REGULAR (daily) testing of your water's chlorine and pH levels, the less trouble you'll have. It's easy. It's quick. It's cheap. It works. Why go any other route?

Because I am consistent in my testing, I spend very little time on taking care of my water. I'm aware of, and ahead of potential problems and have compensated before hand.

I believe in the methods espoused here because I have been using them for 6 years and they work flawlessly. I have had one MINOR algae bloom and that was cleared up in 24 hours--and due to my breaking my own rules. I have not had cloudy water, or any other major problems. But I did have problems before that, when I was using the pool store and "How to Tame the Pool Monster" for advice and hadn't found PoolSolutions.com or Poolforum.com/pf2.

[haze_1956]

PolyQuat should NOT be used when fighting algae.

You have said that on a quite a number of posts Carl !

But what exactly do you base that statement on ?

Ben even recommended using it against an existing bloom this year, although from what I gather it was as a last resort. However it did prove to be successful.
.

[chem geek]

The theory is that PolyQuat disrupts the algae cell membranes thus bursting (or opening up) the cells and killing nascent algae. However, this is a somewhat slow process so it works well with algae trying to grow (stuff falling into the pool and trying to establish itself), but doesn't work well with large quantities of algae as it would take a lot of polyquat to deal with it (and is much more expensive than chlorine). Also, some types of established algae (and bacteria) form biofilms which are resistent to chemical penetration and would tend to block the PolyQuat from killing the cells underneath the biofilm. High chlorine concentrations will eventually breakdown such biofilms and utlimately get to what's lurking below (for black algae, brushing is also required).

At least that's the theory.

I think Ben's recommendation of using PolyQuat as a last resort is so that one has multiple actions going on at once. However, what we have recently discovered is that the shock levels in Ben's table are not sufficient for mustard/yellow algae, but we do seem to have figured that one out by using higher chlorine levels (about 1.0 ppm disinfecting chlorine).

What I'm trying to figure out is what the proper application of PolyQuat would be when closing a pool since generally one uses a shock amount of chlorine and I am concerned that this would breakdown the PolyQuat defeating the purpose of using it. I'm not suggesting abandoning the use of PolyQuat -- just figuring out when it is most effective, perhaps when chlorine levels are lower (normal) rather than when shocking. So my proposal might be (with real-world verification) to use PolyQuat first at normal chlorine levels, wait a week, then use shock chlorine levels and close the pool, OR vice versa (shock levels of chlorine first, then when the chlorine drops to more normal levels, use PolyQuat and close the pool).

Another option is to use 50 ppm Borates instead of PolyQuat and that seems to have the advantage of inhibiting algae without breaking down from chlorine the way that PolyQuat *may* do. It will be interesting to see if Borate levels are maintained over the winter with those people who are now using it.

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,:eek: it would be nice to know what’s happening.:(

[haze_1956]

As to closing a pool, at least where the water temp drops below freezing.

Provided you use a solid cover that blocks the light, little or no algae should grow even at higher temps during fall. And any algae still alive should be killed over the winter by the low tempertures?

Seems to me that if you put a winter cover a green algae pool, that algae should die over the Winter due to low temp and lack of light and you should find a clear pool with the bottom covered with dead algae come Spring.

That seems logical to me, but does it hold true?
.

[chem geek]

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,:eek: it would be nice to know what’s happening.:(
The change in chlorine of 2.2 ppm is 2.2 mg/liter or 1.2 moles per 10,000 gallons. The PolyQuat was 10 ounces (which I assume is fluid ounces liquid) which has 204 grams of PolyQuat which is 0.806 moles for one "poly" which has two nitrogen. Normally it takes at least 3 chlorine for 2 nitrogen to oxidize ammonia so this works out almost exactly correct in this case since (3/2)*0.806 = 1.21. In other words, it does appear that the chlorine indeed breaks down polyquat through breaking at the nitrogen and producing nitrogen gas (just as it does with ammonia). This would leave some other simpler organic compounds to oxidize, but these tend to be broken down much more slowly, possibly requiring sunlight and much more time. In other words, I would expect more chlorine to get used up, but over a longer period of time.

So unless your numbers were just a coincidence, it appears that PolyQuat is broken down by chlorine very much as if it were ammonia (since it is, in fact, an ammonium compound). To me, this means that using PolyQuat in the presence of chlorine doesn't make much sense. Perhaps in the presence of smaller amounts of chlorine the PolyQuat forms something akin to monochloramine and that this is what is effective against algae, but that eventually this breaks down more completely (rather quickly, it seems) just as a monochloramine would break down to nitrogen gas.

(I assumed that because PolyQuat is Poly{ oxyethylene (Dimethyliminio) Ethylene (Dimethyliminio) Ethylene Dichloride} that this is the following chemical formula:

http://www.chemblink.com/products/31512-74-0.htm

http://www.chemblink.com/structures/31512-74-0.gif

so molecular weight is 253.17 for each "poly" which has two nitrogen)

[CarlD]

I cannot argue with Chem_Geek's chemistry--it may well be that I've been wasting money using polyquat in large amounts prior to closing.

But I have noticed too many times for it to be coincidence that adding polyquat will drop FC levels precipitously, but I've never gotten algae as a result. I've also found that 24 to 48 hours after the polyquat dose, that not only is the FC down, but that I can raise it back where I need it with predictable amounts: IE, 6% bleach will add 6ppm to 10,000 gallons.

I am looking to get my water perfectly clean prior to closing, and wait till it's 60 deg or lower to shut down. (actually, I just completed this process).

Is the poly causing the FC to fall by being metabolized by it? If so, is there any left when I then shock? If not, is there ANY point to using PolyQuat? Ben has given PolyQuat his recommendation only for prevention, and suggests avoiding ALL other algaecides.

I'm not versed in chemistry, I've been going on what seems to work. If it's based on nonsense, and it may well be, I will change both my recommendations and my practice. Chem_Geek seems to be one of the most knowledgable chemistry geeks (;) ) on the forum.

But I have ALWAYS felt that shocking your pool up and keeping it up to the max FC level prior to closing is the way to ensure clean water in the spring, and I see no reason to change that recommendation.

[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]

As to closing a pool, at least where the water temp drops below freezing.

Provided you use a solid cover that blocks the light, little or no algae should grow even at higher temps during fall. And any algae still alive should be killed over the winter by the low tempertures?

Seems to me that if you put a winter cover a green algae pool, that algae should die over the Winter due to low temp and lack of light and you should find a clear pool with the bottom covered with dead algae come Spring.

That seems logical to me, but does it hold true?
.
You also asked earlier if chlorine will breakdown detergents and the general answer is that chlorine will breakdown every organic compound in your pool eventually. It's just that this can be quite slow for certain organic compounds. Generally, chlorine is extremely fast (probably seconds) at combining with ammonia to form monochloramine. It is a little slower (probably a few minutes) to combine with nitrogenous organics to form chlorinated organics. It is then slower (probably minutes to hours) at breaking down monochloramine into nitrogen gas and may take even longer to break down the chlorinated organics, though sunlight might help this process. Pure organics not containing nitrogen would probably take the longest to breakdown.

The PolyQuat isn't just a detergent. What mostly characterizes a detergent (and most clarifiers, for that matter) is a molecule that has a polar (charged) end and another that has a non-polar (uncharged or neutral) end. The non-polar side tends to embed in non-polar organics while the polar side has affinity for water. So the net effect is to cover or engulf non-polar organics presumably letting them filter out better -- that is, PolyQuat is really a clarifer and in fact was used as such before it became known that it was a good algaecide.

You are correct that if you cover your pool to keep out sunlight and the pool water stays cold, then algae should not grow (I think the algae just becomes dormant in cold temperatures -- it probably doesn't get killed unless the water freezes which would burst the cells). However, I do seem to recall some photos on this forum where people have opened up their pool to a green mess and then shocked to get rid of it and I seem to recall such pools being covered. Perhaps the weather warmed up enough that the algae primarily grew just before the cover was taken off, and perhaps the cover wasn't opaque (I don't remember). At any rate, it doesn't take long for green algae to "bloom" and fill a pool.

Richard

[chem geek]

I just wrote an E-mail to Buckman Laboratories regarding this issue of chlorine breaking down PolyQuat so we'll see if they respond. I'll keep y'all posted. We'll get to the bottom of this eventually.

Richard

[CarlD]

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).

That all adds up. I probably would have had FC of 15ppm.

The next question (and Buckman may answer it) is whether PolyQuat and Chlorine are working together or fighting. Is there a residual that PQ leaves that continues to be effective against algae growth? Or is it gone?

(BTW, if this gets more technical I'll move it to the China Shop.)

[chem geek]

(BTW, if this gets more technical I'll move it to the China Shop.)
Perhaps you didn't notice, but we are already in The China Shop! I started the thread here because I knew the issue was controversial and not for newbies, though I wasn't sure how technical it was going to get (of course, I tend to make things go that way...:D ).

And your point is quite valid of whether the chlorine breaks down PolyQuat, thus defeating the purpose of using it, or if it combines with PolyQuat to form a potent compound to inhibit and kill algae. Hopefully we'll find the answer to that soon.

Richard

[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

[fcfrey]

I just wrote an E-mail to Buckman Laboratories regarding this issue of chlorine breaking down PolyQuat so we'll see if they respond. I'll keep y'all posted. We'll get to the bottom of this eventually.

Richard

I guess you haven't heard anything yet from Buckman Labs. From all you've written it sure sound like Quat may be a waste if you follow the BBB method.

[chem geek]

I guess you haven't heard anything yet from Buckman Labs. From all you've written it sure sound like Quat may be a waste if you follow the BBB method.
I haven't heard from them yet and just sent a reminder E-mail. I doubt that PolyQuat is a waste at normal chlorine levels. The chlorine may only combine with PolyQuat relatively slowly at normal levels -- perhaps over a weeks time (given that it takes around 1-2 days at high chlorine levels) and the PolyQuat may be quite effective at preventing algae during that time. Also, I don't know yet if the chlorine combining with PolyQuat reduces its effectiveness (i.e. does it form a combination substance that is still useful or does it breakdown PolyQuat rendering it useless). So we'll still need to wait and see what Buckman says.

Richard

[chem geek]

I received the following response from Buckman Laboratories:
Mr. Falk:

Sorry about the delay in getting back to you. I've been checking into some
literature references and trying to contact some of our water treatment
specialists to find some answers to your questions.

1) The Polyquat 60 product that you mentioned is typically used along with
chlorine at normal use concentrations (low ppm levels of both substances) in
swimming pools. Chlorine provides a faster kill of bacteria, while the
Polyquat 60 provides better control of algae as well as better water clarity.
The different advantages of these two pool treatments complement each other.

2) While chlorine and Polyquat 60 have been shown to have very little
interaction at low concentrations, there can be some reaction or degradation
at higher concentrations. For example, Polyquat 60 and bleach should not
be mixed neat, as an undesirable reaction would be expected to occur.

3) In an alkaline solution containing an oxidizing agent, the polymer that
comprises the active ingredient in Polyquat 60 can be cleaved at the sites of
the quaternary ammonium groups, forming shorter polymer chains. These
shorter chains are still cationic; and, according to some internal lab data
here at Buckman Laboratories, these shorter chains retain their biocidal
activity. As the chains become shorter, the Polyquat test kit will not longer
respond to and detect them; however, the lack of a response by the test kit
does not necessarily indicate that the biocidal activity has been lost.

4) In our recommended approach for winterization, the pool should be
"shocked" with about 5-10 ppm chlorine to destroy any lingering oxidant
demand, to remove any residual ammonia or chloramine, etc. After a
couple of days, adjust the pH back to 7.2-7.6 and add Polyquat 60 at the
maximum rate allowed by the label. This approach allows you to have the
maximum benefit from both chemicals.

If you have any other questions, please do not hesitate to contact us.

Tom McNeel
Principal Scientist
Buckman Laboratories International, Inc.
So there does appear to be consumption of chlorine by the PolyQuat (shock chlorine has high FC levels and increases the pH of the pool) and this is probably cleavage at the Nitrogen site, but the remaining chains are still effective as an algaecide. However, the recommendation is to first shock with chlorine (mostly to get rid of most organics and/or ammonia in the pool) and then wait for the FC to return to normal levels and make sure the pH is in the normal range. Then, add the PolyQuat in the recommended amount for closing the pool.

In addition to the E-mail, I talked with Dr. McNeel and asked about the method of action of PolyQuat on algae and he said that the cationic nature of the molecule (that means it has positive net charge) binds to and interferes with the negatively charged cell exteriors of most algae and bacteria and prevents the normal transport of food into the cell and waste out of the cell. This process is somewhat slow so it's fine for inhibiting algae, but not quite fast enough to quickly kill bacteria so chlorine is still required for disinfection. This method of action is for the hydrophillic (i.e. "water loving") PolyQuat molecules. There are other quarternary ammonium compounds that are hydrophobic (i.e. "water hating") that operate with a different method of action, but we didn't get into details on that.

He also said that while PolyQuat inhibits and kills algae, it does not harm people, either through skin exposure nor consumption (i.e. drinking pool water that has some PolyQuat in it). [EDIT] Dr. McNeel sent a follow-up E-mail saying that after adding PolyQuat, the circulation pump should be kept running for at least 24 hours to thoroughly distribute it through the pool. My guess is that the heavy molecular weight of the PolyQuat (it's a long-chain polymer) makes it slower to diffuse so lots of circulation is needed. [END-EDIT]

Thanks,
Richard

[waterbear]

Another option is to use 50 ppm Borates instead of PolyQuat and that seems to have the advantage of inhibiting algae without breaking down from chlorine the way that PolyQuat *may* do. It will be interesting to see if Borate levels are maintained over the winter with those people who are now using it.

Richard
I don't close my pool for the winter but the water has gotten colder (about 45- 50 deg. now if I don't turn on the heater) and my borate levels are still at 50 ppm. I am running my FC at about 3 ppm in this colder weather (swg at 4% and pump run time of 6 hours) and pool is still clear and sparkling. Have not added acid in 2 months and pH is still 7.6. From what I have seen so far borates, when properly dosed, seem to be very effective at reducing sanitizer demand. We shall see what happens as the winter progresses.