Closing chemistry recommendation

[FormerBromineUser]

Somewhere ChemGeek responded to this issue after talking with one of the 'manufacturers' of polyquat. I believe he said that the shorter threads still do their job. But understanding ChemGeek is not my speciality!!!!

[chem geek]

See this post where you can read the procedure from Buckman Labs. They also told me that when chlorine oxidizes Polyquat into smaller pieces, they are still fairly effective. They just won't act as much like a clarifier, but can still inhibit algae growth.

[FormerBromineUser]

Ah, you wrote in English. Your response was just basic enough for us non-chemgeeks to understand.

It is important information for those of us who ponder using polyquat on closing. The clarifying properties seem pretty insignificant at the end of the season.

I would love to see this info put out there for easier access on the Pool Forum.

[CarlD]

See this post where you can read the procedure from Buckman Labs. They also told me that when chlorine oxidizes Polyquat into smaller pieces, they are still fairly effective. They just won't act as much like a clarifier, but can still inhibit algae growth.

My winter closing procedure and spring opening results is a demonstration of that.

[SunnyOptimism]

So here's how I'm reading the info in this thread-

You bring you water to shock level to clear it.

You wait some amount of time and then add polyquat

You wait a little longer and then raise your FC again and close.

The problem I see is that, based on the manufacturers recommended process, if you follow the CYA/FC relationship (as you should) then your shock level of FC is definitely going to cleave the PQ into smaller subunits unless you wait long enough after shock level for the FC to drop below 10ppm. If you look carefully at what the manufacturer says, they say to shock up to 5-10ppm and then "wait a few days" before adding the PQ. That tells me that the PQ is definitely going to cleave.

I guess the ultimate question is, at what FC does PQ start to cleave into smaller fragments and at what FC is the PQ's algaestatic properties completely destroyed? That last part would set the upper bound of how much FC you can have in the water when you add the PQ. Add the PQ too soon after raising the FC to shock level and you risk the chlorine burning up all your PQ.

Interesting stuff here.....

[JimK]

So here's how I'm reading the info in this thread-

You bring you water to shock level to clear it.

You wait some amount of time and then add polyquat

You wait a little longer and then raise your FC again and close.

The problem I see is that, based on the manufacturers recommended process, if you follow the CYA/FC relationship (as you should) then your shock level of FC is definitely going to cleave the PQ into smaller subunits unless you wait long enough after shock level for the FC to drop below 10ppm. If you look carefully at what the manufacturer says, they say to shock up to 5-10ppm and then "wait a few days" before adding the PQ. That tells me that the PQ is definitely going to cleave.

I guess the ultimate question is, at what FC does PQ start to cleave into smaller fragments and at what FC is the PQ's algaestatic properties completely destroyed? That last part would set the upper bound of how much FC you can have in the water when you add the PQ. Add the PQ too soon after raising the FC to shock level and you risk the chlorine burning up all your PQ.

Interesting stuff here.....

I was wondering about that also.

[CarlD]

Not me. I've been using an effective method of closing for over a decade.

[amillionpets]

I've read this entire thread plus other helpful closing information on the site. THANK YOU!

My question: When you refer to raising the FC to shock level to close, at what point on the "Ben's Best Guess Guide to Swimming Pool Chlorine" are you shocking? There are two 'Shock' columns with very different Shock levels. Should we use the higher shock numbers for winter closing?

[CarlD]

No. Use the lower value, I believe the left of the 2 columns. I do not recommend you closing your pool until any algae bloom is clear. Then raise to the lower shock level.
If your CYA level is below 10, use 10 as your shock level
Below 30, use 12.
Below 60, use 15,
Below 100, use 20,
100 or above, use 25.

[FormerBromineUser]

They also told me that when chlorine oxidizes Polyquat into smaller pieces, they are still fairly effective.

And the question is???

If you want the assurance of an algaecide on closing, and also want to close with shock level FC, this is your answer. "Fairly effective" sounds like a plan.

Doesn't seem like allowing FC to drift down before adding polyquat makes a big difference when you close at shock level because your FC will still attack the PQ.