PolyQuat and Shocking with Chlorine

[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

[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.

[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).

[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... ).

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