Concerns about closing my older fiberglass pool at shock level

lilac1

New member
Oct 27, 2020
3
KY
I’ve got a 20-year old fiberglass pool with a mesh cover. Water temperature is now 60 degrees so I thought I’d skip the polyquat this year since it doesn’t seem to help and just close at shock level. I’m concerned, however, about the effect the high chlorine level will have on old our mesh cover and the fiberglass. My mesh cover and gelcoat aren’t in the best shape, and I had a crack in the shell a few years ago that was patched, so I’m a bit worried that a chlorine level of 20 ppm for so long could be damaging. If a chlorine level that high could be damaging to the fiberglass or our old mesh cover, could I close with a lower chlorine level than this and just add more chlorine later this fall or winter, if we get some unseasonably warm weather? Since my pool will be covered and the water will be cold, is it really necessary to get the FC all the way up to 20 ppm at closing?
 

ajw22

Gold Supporter
TFP Guide
Jul 21, 2013
23,586
Northern NJ
Pool Size
35000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-60
Welcome to TFP.

What is your CYA?

Why do you think you need a FC of 20 to close?
 

lilac1

New member
Oct 27, 2020
3
KY
Welcome to TFP.

What is your CYA?

Why do you think you need a FC of 20 to close?
My CYA is 50 so I assumed that I needed to close with a FC of 20. I’d like to close with a lower FC level or use polyquat at closing if that high of a FC level could be potentially harmful to my mesh cover or fiberglass.
 

ajw22

Gold Supporter
TFP Guide
Jul 21, 2013
23,586
Northern NJ
Pool Size
35000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-60
My CYA is 50 so I assumed that I needed to close with a FC of 20. I’d like to close with a lower FC level or use polyquat at closing if that high of a FC level could be potentially harmful to my mesh cover or fiberglass.

Close with a FC around half SLAM FC level or around 10 for you and add Polyquat 60 if you want. Read about PQ60 use at...

 

lilac1

New member
Oct 27, 2020
3
KY
A pool service is closing my pool tomorrow. I bought some polyquat 60 algeacide to add before closing. A week ago, I shocked my pool and it has finally drifted down close to half shock level - 11 (cya is 50). Last night and this morning, the remnants of Hurricane Zeta came through here so I tested my water a little while ago to make sure I didn’t need to add anything to the water before adding the polyquat. I found that the PH has gone up to 7.8 and CC went up to .5. Water looks clear but it was full of leaf debris before I cleaned it. Do I need to add any muriatic acid before closing or is the higher PH inconclusive because of the 11 ppm chlorine level or recent rainfall? I normally shock my pool after a bad storm but I assume that I shouldn’t do this because I read that high chlorine oxidizes the polyquat. Should I add a phosphate remover because of all of the debris that was in the pool or will the polyquat sufficiently protect the pool from algae?
 

ajw22

Gold Supporter
TFP Guide
Jul 21, 2013
23,586
Northern NJ
Pool Size
35000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-60
What is your TA?

Just add the PQ60 and close the pool.
 
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