Closing tomorrow and FC is too high for using polyquat

[Venus2]

I followed the advice on pool school for closing an inground pool and got my FC up to SLAM level 3 days before closing and I’ve been waiting for FC to drop to half SLAM level so I could add polyquat. Even though the water temperature is 65 degrees and highs have been in the upper 70s on these days, FC has only gone down 3 ppms. I seriously doubt that we will lose more than 1 ppm today, so the chlorine level will be higher than recommended for adding polyquat by tonight when I planned on adding the polyquat for tomorrow’s closing. Since the water temperature is 65 degrees and we have a mesh cover, is it too risky to close without the polyquat or could it be added even though the FC is 5 ppms more than half SLAM? I’ve already purchased the polyquat but can return it for some chlorine. It would be easier to close without the polyquat so I’d like to do that instead unless it would be too risky to skip the polyquat because of the 65 degree water temperature and mesh cover. Since I’m worried about the chlorine bleaching my gelcoat, could I just close with the 14-15 ppms of chlorine that I have now and add more chlorine when draining water out of my pool later this fall? I was told by my manufacturer to never add more than 10 ppms of chlorine to my pool so I’m hesitant to add more chlorine to get back up to 16 ppms. I don’t quite understand why it is safe for a pool with a CYA of 40 to close with 16 ppms of chlorine but it is only safe for a pool with a CYA of 30 to close with a CYA of only 12 since the pool will be covered. Would someone care to explain this? The CYA often drops to below 30 over the winter because of all of the water additions and draining so would it be okay to close with 14 ppms of chlorine instead? If CYA goes down below 30 before the FC drops, could my gelcoat be harmed?

 

[Bperry]

I followed the advice on pool school for closing an inground pool and got my FC up to SLAM level 3 days before closing and I’ve been waiting for FC to drop to half SLAM level so I could add polyquat. Even though the water temperature is 65 degrees and highs have been in the upper 70s on these days, FC has only gone down 3 ppms. I seriously doubt that we will lose more than 1 ppm today, so the chlorine level will be higher than recommended for adding polyquat by tonight when I planned on adding the polyquat for tomorrow’s closing. Since the water temperature is 65 degrees and we have a mesh cover, is it too risky to close without the polyquat or could it be added even though the FC is 5 ppms more than half SLAM? I’ve already purchased the polyquat but can return it for some chlorine. It would be easier to close without the polyquat so I’d like to do that instead unless it would be too risky to skip the polyquat because of the 65 degree water temperature and mesh cover. Since I’m worried about the chlorine bleaching my gelcoat, could I just close with the 14-15 ppms of chlorine that I have now and add more chlorine when draining water out of my pool later this fall? I was told by my manufacturer to never add more than 10 ppms of chlorine to my pool so I’m hesitant to add more chlorine to get back up to 16 ppms. I don’t quite understand why it is safe for a pool with a CYA of 40 to close with 16 ppms of chlorine but it is only safe for a pool with a CYA of 30 to close with a CYA of only 12 since the pool will be covered. Would someone care to explain this? The CYA often drops to below 30 over the winter because of all of the water additions and draining so would it be okay to close with 14 ppms of chlorine instead? If CYA goes down below 30 before the FC drops, could my gelcoat be harmed?

Polyquat breaks down in higher chlorine so if you add it now it’s just going to be wasted. Better to wait until the chlorine level is lower or just save it for next season.

 

[JJ_Tex]

CYA acts as a buffer for chlorine, so you have to look at them as a ratio. The higher your CYA, the higher your FC should be, which is why the SLAM target for 40 CYA is 16, but 30 CYA is only 12.
Also keep in mind that the FC/CYA ratio is "new" thinking, and most of the pool manufacturers still give advice from the 1950's when CYA was not added to pools so they just had a set FC target with no regard to CYA.

I'm by no means an expert on closing or using ployquat, but if you are targeting 1/2 SLAM target and cannot get your FC down fast enough, can you raise your CYA? If you raise your CYA by 10 to 50, 1/2 SLAM would be FC of 10.

 

[Newdude]

could I just close with the 14-15 ppms of chlorine that I have now and add more chlorine when draining water out of my pool later this fall?

Absolutely

was told by my manufacturer to never add more than 10 ppms of chlorine to my pool so I’m hesitant to add more chlorine to get back up to 16 ppms.

The industry shuns the science of the CYA and FC relationship. Science says that SLAM FC is less harsh than tap water.

I don’t quite understand why it is safe for a pool with a CYA of 40 to close with 16 ppms of chlorine but it is only safe for a pool with a CYA of 30 to close with a CYA of only 12

CYA buffers the chlorine so the more CYA you have, you need proportionately more FC for all things to be equal. All lines on this chart are considered equal.

The CYA often drops to below 30 over the winter because of all of the water additions and draining so would it be okay to close with 14 ppms of chlorine instead? If CYA goes down below 30 before the FC drops, could my gelcoat be harmed?

Both will drop at similar rates from dilution, and the FC may go faster due to UV and organics. Your gelcoat will be fine.