Chlorine went down to 0 - must I shock?

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Lilypad said:
Agree that the filter could be what's contributing to the FC loss. I'd open it up and see if it needs a good cleaning.
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The shock level water is flowing through that filter. It does not harbor live algae. No way.

Aubade - you said you found the pool with 0 CYA this spring and added to 70. You have tested that again recently, right?

CYA does degrade naturally about 3-5 ppm per month. It also can be attacked by a bacteria that creates ammonia that take a significant amount of chlorine to eradicate. But once the pool holds FC and CYA, the bacteria is dead.

Good luck.
 
We did clean the filter. It's a cartridge filter so my husband took it out and hosed it down really well. He said it was dirty but not algae - just dirt. (in june put down grass seed and a lot of dirt blew into the pool until it grew in so that's probably why.)

I did check the CYA a couple times last week and it is 55 - 60ish.
 
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I’m seeing a good bit of guessing going on which is concerning here. Let’s take a quick second and pull things back together.

Can you help us be answering a few quick questions.
1. What test kit are you using?
2. Can you post a full set of current results using your FAS/DPD kit?
3. How does your water look?
4. When did you last do an OCLT and what were the results??
 
This is all on the first page but since now we're on p 3 (!) here it is again. You can see a pic of the water on p.1 too.

Leebo said:
I’m seeing a good bit of guessing going on which is concerning here. Let’s take a quick second and pull things back together.

Can you help us be answering a few quick questions.
1. What test kit are you using? Taylor K-2006

2. Can you post a full set of current results using your FAS/DPD kit?

This was from July 28th, the last time I did a full test:
3.5 FC
7.4 pH
110 TA
105 CH

I did CYA a couple times after that and it was 55ish, 60 if I round up.

3. How does your water look? sparkling clear

4. When did you last do an OCLT and what were the results??
We've been testing every evening when the sun is off the pool and again first thing in the morning.

Thurs night it was 21. We raised it back up to 24 and by morning it was 19.

Last night it was 16 then i forgot to do it this morning and just now at 1:28 with full sun on the pool it is down to 18. CC has been 0 for days each time I test.
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Chlorine is consumed by organics or sunlight.

Since you have tested a proper amount of CYA, your sunlight loss is controlled.

Organics, you have reported not adding any pool store potions in the past that need to be oxidized so it is something in the water, under a ladder, inside a light fixture, the skimmer weir door, or somewhere.
 
OK last night I got in there and scrubbed everything down thoroughly. The walls, the corners where the walls meet the bottom, the returns, all over and under the ladder, the lights, the steps, the skimmer door. I didn't really see anything, though I suppose there was a little film & it did look a bit better afterwards. After we finished swimming it was down to 12 so we brought it back up to 24. This morning it was back down to 19.

The lights are S.R. Smith Treo LED lights. There's 3 of them. I scrubbed them, but they seem pretty contained. I got out the instructions and it looks like you'd have to drain the pool to below the light level to pull them out and I'd be way too nervous to do that since I know you have to be super careful when draining fiberglass pools. (we had the pool company close it and open it last year just to be safe)
 
Good job! Stay at the shock FC today diligently.

I think you are good on the lights. A quick review of the owners manual showed they should be sealed.

Good luck!
 
thanks so much, i really appreciate all your help!

just one more question - how long do you have to wait after adding liquid chlorine to test whether you really got it up to 24? I imagine this might also depend on whether you have the filter going or not (since that would disperse it more quickly). I usually take my water samples from the deep end of the pool, as far down as I can reach (like elbow deep), but I add the liquid chlorine at the low end where the jets shoot the water out from the filter.

We've been keeping the filter on almost all the time, but just now it wasn't on when I added 52 oz of the liquid chlorine. I tested right afterwards from the deep end and it was still only 19. So i'm just curious if that was because it hadn't dispersed yet. (could also have been because i took the last reading before breakfast and now the sun has been on the pool for a few hours, so maybe it was lower and I need to add more)

I turned the filter on and will test again in a few but just wondering if you had some guidelines for how long to wait to test after adding it.
 
During a SLAM the typical process is to test your FC, say it is 19. Use PoolMath to calculate an add to 24. Add that amount of chlorine. Do not test until you get to your next check time. Unless you do not a reasonably accurate pool volume, or you unsure of the quality of your liquid chlorine, there is no need to test after you add the chlorine.

Take care.
 

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Still not working. *sigh* I scrubbed it again on Sunday and we're adding chlorine around 9 am, 12 noon, 4 pm and 8 pm. It got a bit better - only went down to 20 instead of 16-19 - but still doesn't pass the OCLT. :confused:
 
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