preventing algae when closing with a mesh cover before water temperature is below 60 degrees

nadar

Member
Oct 21, 2018
22
Northern Tennessee
My pool closing is scheduled for Friday. Water temperature is 65 degrees, which is higher than it usually is this time of year. Unfortunately, I can't change the closing date so I need to know what I can do to prevent algae from developing before the water temperature gets colder. I assume that I need to use polyquat as insurance since water temperature is 65 degrees, so I shocked on Sunday and I'm waiting for the FC to drift down to half-shock level (12 ppm) before adding the polyquat. It looks like I'm going to get to half-shock level a day earlier than anticipated, so I'm wondering if I should bump the chlorine back up to half-shock level (12 ppm) the day before closing before I add the polyquat. If I need to do that, how long do I need to wait after adding the chlorine before adding the polyquat? Also, if the FC dips down below target level after it is added, should I bump it back up to target level (7 ppm) or higher before closing? Last year, when I added the polyquat to 60-degree water at half shock level, it lowered my FC to below target level but I didn't bump it back up. I just want to make sure I know what to do if this happens again. I'd also like to know if there is anything else I can do to prevent algae before the water turns colder. Would it help if I put a few tarps over the top of the cover to block out some of the sun since I have a mesh cover that lets in some light?
 

ajw22

Gold Supporter
TFP Guide
Jul 21, 2013
10,413
Northern NJ
My pool closing is scheduled for Friday. Water temperature is 65 degrees, which is higher than it usually is this time of year. Unfortunately, I can't change the closing date so I need to know what I can do to prevent algae from developing before the water temperature gets colder.
65 is close enough to 60 to not worry about it.

I assume that I need to use polyquat as insurance since water temperature is 65 degrees, so I shocked on Sunday and I'm waiting for the FC to drift down to half-shock level (12 ppm) before adding the polyquat. It looks like I'm going to get to half-shock level a day earlier than anticipated, so I'm wondering if I should bump the chlorine back up to half-shock level (12 ppm) the day before closing before I add the polyquat.
The exact FC level is not that important. Anywhere between half SLAM level and your normal level is fine.

If I need to do that, how long do I need to wait after adding the chlorine before adding the polyquat?
You don't need to add chlorine and you can add both at the same time if you wanted to.

Also, if the FC dips down below target level after it is added, should I bump it back up to target level (7 ppm) or higher before closing?
No.

Last year, when I added the polyquat to 60-degree water at half shock level, it lowered my FC to below target level but I didn't bump it back up. I just want to make sure I know what to do if this happens again.
Don't do anything. The PQ and the CL interact as designed. Adding more CL will breakdown more PQ.

Read How_To_Use_Polyquat_60_in_Pool_Winterization?

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

Buckman Labs says that the Polyquat that is broken down is still effective as an algaecide. Moderate to high levels of chlorine break down polyquat, but only turn it into shorter chain polymers that are still effective.


I'd also like to know if there is anything else I can do to prevent algae before the water turns colder. Would it help if I put a few tarps over the top of the cover to block out some of the sun since I have a mesh cover that lets in some light?
I doubt the tarps will make any real difference. Open your pool as early as possible to prevent algae growth in he Spring.
 

Catanzaro

Platinum Supporter
TFP Guide
Jul 30, 2014
3,401
Monmouth County, New Jersey
Would it help if I put a few tarps over the top of the cover to block out some of the sun since I have a mesh cover that lets in some light?
As Allen mentioned before, the tarps will probably not help you if you are closing now as the water is cold, and 60 to 65 degrees will make no difference.

However, if you close real early in September, then adding tarps over the mesh cover until the water temperature drops below 60 degrees is a good idea. The only thing I can tell you is that we have used this method for late September, but opened the pool early early (at least one month before the Holiday), and there was no algae. In the previous years, we developed algae. There are a lot of factors to consider.

I have a solid tarp and this year, I closed my pool the last week of September. I always open the month prior. Whether I close in the middle of September or late October, the key is also to open up early. I have never had any algae with a solid tarp. I close with Poly 60, and chlorine levels slightly less than 50%, maybe between the 50% mark and my normal CYA/FC ratio. I would still recommend Poly 60 upon closing for your pool.

Please keep us posted next year when you open the pool as well. Thanks!