I should say as you get closer to SLAM level or over SLAM level, the chlorine can dissipate even faster. It sounds like your safely below SLAM so you have some time to go still.
Pool Chlorine Level Keeps Dropping (Please help! Incurring astronomic costs in chemicals)
- Thread starter qsch1
- Start date
- Jun 1, 2018
- 14,116
- Pool Size
- 26000
- Surface
- Vinyl
- Chlorine
- Salt Water Generator
- SWG Type
- Hayward Aqua Rite (T-15)
So finally, it seems like we have done it! Phew, I didnt expect it to take so long to be honest (about 2 weeks or more). So last night I did the 10 ml FC test with only pool water and the result was 36 and this morning (albight a little after the sun came out) I did it again and it was 34. This means it only dropped 1 point (18, then 17 today). CC is .5, it turned a little pinkish after the FC test and then one drop cleared it again. So I think that is it?
It's a pass. 
Normally I don't like to borderline pass, but with the solar pump not able to mix at either half of the OCLT, I feel better about it.
I'd feel even better about it if you got a 2nd pass tonight. A little bit of insurance goes a long way.
Normally I don't like to borderline pass, but with the solar pump not able to mix at either half of the OCLT, I feel better about it. I'd feel even better about it if you got a 2nd pass tonight. A little bit of insurance goes a long way.
- Jun 1, 2018
- 14,116
- Pool Size
- 26000
- Surface
- Vinyl
- Chlorine
- Salt Water Generator
- SWG Type
- Hayward Aqua Rite (T-15)
Whooooo Hooo! 
Congratulations!
It is preferable to be at slam fc level for the oclt but we’ll call it a win.
Pool still crystal clear (no accumulation dead or alive)?
Lets see if @Newdude thinks you should do one more Overnight Chlorine Loss Test @ slam level.
Congratulations!
It is preferable to be at slam fc level for the oclt but we’ll call it a win.
Pool still crystal clear (no accumulation dead or alive)?
Lets see if @Newdude thinks you should do one more Overnight Chlorine Loss Test @ slam level.
8 to 10 is just as good, or however far it drifts down today. It either loses more than 1ppm (at 8, 10........ 20?), or it doesn't.
At worst, with a fail, no progress is lost and it was a momentary pause in the action.
Or it passes and they're that much closer to target range to resume normal operation.
- Mar 5, 2020
- 3,211
- Pool Size
- 66000
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- Astral Viron V35
Well done!
Make sure that your FC never drops too low, and you should never have to go through that again.
I'd stick to the higher end of the target range, that gives you more buffer time to realise that something went wrong. It may for example take you a few days to realise that the SWG is not producing anymore.
Remember that you can safely swim with FC up to SLAM-FC. But having FC drop too low can let algae back in which can quickly eat more chlorine than your SWG can produce, turning the water unsanitary very quickly. Always err on the high side of FC, not on the low side.
Make sure that your FC never drops too low, and you should never have to go through that again.
I'd stick to the higher end of the target range, that gives you more buffer time to realise that something went wrong. It may for example take you a few days to realise that the SWG is not producing anymore.
Remember that you can safely swim with FC up to SLAM-FC. But having FC drop too low can let algae back in which can quickly eat more chlorine than your SWG can produce, turning the water unsanitary very quickly. Always err on the high side of FC, not on the low side.
I run hot becasue I'm lazy. Having a 2 or 3 day supply of reserve FC means I have that long to catch the FC being low, without having to babysit it.
If I tested it the other day and the SWG lights are green, I don't need to test today. Whether I'm chasing a dog, a kid, or picking up something the wind blew off the patio, I pretty much see the SWG everyday without making a detour to it. Yup. The lights green. Maybe I'll test tomorrow.
If I tested it the other day and the SWG lights are green, I don't need to test today. Whether I'm chasing a dog, a kid, or picking up something the wind blew off the patio, I pretty much see the SWG everyday without making a detour to it. Yup. The lights green. Maybe I'll test tomorrow.
I think I made an error in the FC calculation in the evening. I now recall it was 38 (not 36), which means it was 19 (not 18) and this morning was 34, which means it was 17 (an hour after the sun was up). That means it dropped by an FC of 2 not 1. CC was .5 or lower however. The pool has been crystal clear since at least 10 - 14 days. Do bear in mind that I am in the tropics and there is a lot of salt air here so not sure if that can affect the level somehow.
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It generally drifts down very little if no liquid chlorine is put in. If I miss a day, it drifts down from 24 (slam level) by maybe 5 - 8 points (to 18 - 20), but then again, I leave the chlorinator on during the day, as my pump stops working at night anyway.
- Jun 1, 2018
- 14,116
- Pool Size
- 26000
- Surface
- Vinyl
- Chlorine
- Salt Water Generator
- SWG Type
- Hayward Aqua Rite (T-15)
I think you’re good 
That’s alotttt of drops to count!
You can do the
Overnight Chlorine Loss Test again when fc drops to target levels for your cya to be 100% sure.
It will certainly be easier to count!
In fact anytime things seem off (fc consumption seems high, your fc fell too low etc.) you can do an oclt - don’t wait for a green monster. That’s the beauty of being able to test this way.
That’s alotttt of drops to count!
You can do the
Overnight Chlorine Loss Test again when fc drops to target levels for your cya to be 100% sure.
It will certainly be easier to count!
In fact anytime things seem off (fc consumption seems high, your fc fell too low etc.) you can do an oclt - don’t wait for a green monster. That’s the beauty of being able to test this way.
- Jun 1, 2018
- 14,116
- Pool Size
- 26000
- Surface
- Vinyl
- Chlorine
- Salt Water Generator
- SWG Type
- Hayward Aqua Rite (T-15)
Just letting you know, I did another ONCL test with 10 ml pool water and it was 21 drops the evening after dark, and 21 drops in the morning. Hurrah!
If I remember correctly it was 1 - 2 drops and then it was clear again. I think 0.5.
1 drop would be 0.5ppm and pass
2 drops wouls be 1.0ppm and fail.
yes I realise this, but there was no FC loss overnight as the FC dropped down to around 10 - 11 from slam level of 24. It was still 11 in the morning. I tested CC a few days before this happened and 1 drop was enough to get it back clear for the CC. I can't remember the result after I tested no loss for the ONCL test.
You’re probably fine, but the SLAM ends when all three of the requirements pass at the same time. Having zero CC a few days ago doesnt count. I think if you just wrote down the actual measurements its help you out. The point of getting the test kit is that you dont have to say “around 10-11” anymore because youll know if its 10 or if its 11 and you can just write that one number down.
But you’re probably right, but be careful in the future.
You’re probably fine, but the SLAM ends when all three of the requirements pass at the same time. Having zero CC a few days ago doesnt count. I think if you just wrote down the actual measurements its help you out. The point of getting the test kit is that you dont have to say “around 10-11” anymore because youll know if its 10 or if its 11 and you can just write that one number down.
But you’re probably right, but be careful in the future.
Sorry I meant to say it was 11, but that does not translate to exact FC as it would be 10.5. Thats why I said 10 - 11.