What chlorine level to shock -- now that half my CYA is gone

[PoolDoc]

Losing CYA is a bio-degrative process: no "bio"; no CYA loss.

Covering a pool stops solar loss of chlorine, and it mostly stops algae, but it does not stop bacteria, especially once the chlorine is gone. Maintaining minimal chlorine levels under the cover, will almost certainly stop the process. BUT, one class of the operative organisms is Pseudomonas genus, a group notorious for forming sanitizer resistant biofilms.

Following this process of winterization should do the trick:

1. Stop using the pool at least 1 week before closing (to allow all human added organics, etc to be oxidized and/or filtered).
2. Physically clean the pool at this time, removing all leaves and debris, and brushing thoroughly to break up any forming biofilms.
3. Run the filter 24/7 during the final week. (Same reason). Clean the filter 1/2 of the way through the week, to remove all goop from the filter.
4. Raise the pool to maximum chlorine levels at the beginning of this period. Allow it to drop to high-normal levels by week's end.

5a. Winterize the pool OR
5b. Cover the pool, but do not winterize that that time.

6a. Check weekly while water temps are > 60 degrees to maintain chlorine levels OR
6b. As above, but circulate the water for several hours (or for 1 hour per day every day)

7a. --
7b. Winterize the system, once freezing temps are imminent, or water temp is below 50.

8. Continue to maintain chlorine levels all winter, with monthly checking.

9a. Once water temps rise above 60 degrees, check chlorine weekly.
9b. As above, but also open the circulation system, while leaving the pool covered.

10. Open the pool.

[PoolDoc]

Dave has a point about accumulating chlorine.

If it's not convenient to purchase bleach every other day or so, it may be worthwhile to do a chlorine demand test: http://pool9.net/bucket-demand

[JimK]

I need to print out that post about closing for future reference.

I'll check out that link also.

Thanks.

I'll report again tomorrow.

[JimK]

Day 2...

Hi Ben. I got the items you suggested (borax, OTO/Phenol Red test kit, 8.5% bleach - I have 19 jugs on hand now (121oz each).

I used the OTO kit to check CL and pH to see how it matched up with the Taylor kit.

FC - 0
pH - 7.2 (before adding borax; I'll test again in about an hour)

So it matches the Taylor kit results.

This evening I'll add the bleach as you recommended.

Is it OK to let the pool go all day with 0 CL???

[PoolDoc]

Probably be best to add 1/2 gallon or so.

[JimK]

Probably be best to add 1/2 gallon or so.

I'll do that right now.

[JimK]

I'm curious, with the initial dose of CL eaten up so quick, should I expect to see high CC? (I'm only seeing .5 max). Or does CC get eaten up some how as well?