Confused about FC level and dosage when using Poly-Quat 60 at closing

gwtw

Well-known member
Apr 23, 2018
94
Kentucky
We are closing our pool in a few days with Poly-Quat 60 since the weather has been unseasonably warm this week (low 80s) and the water temperature has risen to 68 degrees. I've read all of the information on here about using Poly-Quat and I'm confused about when to add it and the dosage. The information on Pool School says to add it at half shock level, which is 12 ppm since CYA is 60. A discussion at the top of this page says to add it at normal chlorine level, which would be 7-9 ppm since CYA is 60. I saw another post on here which says to add it at 3-5 ppm, which is a lot less than my normal FC level. Since I'm closing my mesh-covered pool early before the water temperature is below 60 degrees, what is the ideal closing chlorine level to maximize the effectiveness of the Poly-Quat? I understand that it is important not to add it at too high of a chlorine level because the chlorine can oxidize the poly-quat, which can decrease its effectiveness. I also need to know if I need to use the visable algae dose which is 11-17 oz. per 10,000 gallons or the clean pool dose which is 6-11 oz per 10,000 gallons. I don't see any evidence of algae now but a lot of leaves keep blowing into the pool. I'm hoping that the Poly-Quat will help prevent algae until the water turns colder so I want to make sure I add it at the optimal FC level and at the correct dose.
 

ajw22

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TFP Guide
Jul 21, 2013
21,274
Northern NJ
Pool Size
35000
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Plaster
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-60
PQ60 will work at whatever FC level you have when you add it...

From Algaecide - Further Reading

The following is Buckman Labs’ recommendation on how to use Polyquat 60 for closing your pool for the season.

As they recommend for proper winterization, the pool should be "shocked" with about 5-10ppm chlorine to destroy any lingering oxidant demand and remove any residual ammonia or chloramine, etc. After a couple of days, adjust the pH back to 7.2-7.6 and then add Polyquat 60 at the maximum rate as instructed per the label. This approach allows you to receive the highest benefit from both chemicals.

Note that Polyquat and linear quat algaecides are organic compounds that are known to cause interference's with certain color indicating reagents like pH indicators. Adjust the pH before adding Polyquat 60 and there is no reason to test pH after adding it.

Another point that they make regarding using this algaecide in pool water is that after the addition of Polyquat 60, it’s important to keep the circulation pump on for at least 24 hours to make sure that the algaecide is thoroughly distributed throughout the pool.

If you raise your water to SLAM FC level then you should let the FC drift down before adding Polyquat 60. Having a moderately higher level (½ SLAM level so the FC/CYA ratio of 20%) is okay as well. The idea is that the Polyquat should last through the winter even if the chlorine does not.

Buckman Labs says that even if the Polyquat is broken down, it is still effective when used as an algaecide. Moderate to high levels of chlorine break down Polyquat but it still only transforms the formula into shorter chain polymers that are still just as effective.
 
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Texas Splash

Mod Squad
TFP Expert
LifeTime Supporter
You are in familiar company this year. For sure a low FC level is out. Too high and you know it won't last long. So I'd go for the middle of the road (mid-SLAM) with the FC and add the Poly just before shutting her down. As for the dosage, you might err on the side of caution and meet at least the min of 11 oz per 10K just because it's so warm and you have a lot of organic material in the area.
 

Newdude

Well-known member
Jun 16, 2019
4,833
NY
The 5 years I used it I always ‘rounded up’ to the full bottle by at least 1/3. I never noticed any issues but I can’t say that if there were issues I just didn’t know about.
 
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ajw22

Gold Supporter
TFP Guide
Jul 21, 2013
21,274
Northern NJ
Pool Size
35000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-60
What, if any, is the downside to using too much poly? In other words, if I dump a full bottle in there when 1/2 bottle is called for.
No big issue. It may take some chlorine in the spring opening to break down the remaining PQ60.
 
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