Dialing in the right percentage on the chlorine generator

[tsunami]

In mid October, we added salt to our new pool-- initially up to 3500 ppm. It has a Pentair IC40. After superchlorination for the first 24 hrs, we set it to 80%, and later dropped it to 60% since temperatures were starting to drop in late October. I always got a really bright, almost yellow-orange color on my 5 drop chlorine test, and decided to drop it to 20% to see if I could get it down to the 2-4 ppm range. There was no color change, so I dropped it to 10% and it was still bright yellow--probably higher than 5 ppm. So out of curiosity, I took a water sample to a trusted pool store.

He said that my water chemistry was perfect(thanks to TFP!), PH 7.6, TA 80, CYA 60, although my chlorine was sky high. So I decided to set it to 0% until it drops to the 2-4 ppm range. That was 3 weeks ago and it's still bright yellow--probably more than 5 ppm. We hardly used the pool in November because of the cooler temps, but have used the spa only a couple of times since. Currently, the salt level on the indoor controller's at 3000 ppm. I wonder how long it will take to get the chlorine into the proper range? Could my chlorine generator still be generating chlorine even though it's set at 0%?

 

[Strannik]

highly doubt it
you can pull the power plug and compare

i think it's more to do with cooler water and nobody swimming in it

 

[tsunami]

A friend of mine recently finished his new pool, also a salt water pool. So to compare results, I asked him what his chlorine level was and what he set his swcg IC40 at. He said it's at 3400 ppm. I said that's your salt level, not chlorine level. What's your test kit read? He says he doesn't test for chlorine, only ph. He tells me that he doesn't need to test for chlorine because his swg automatically makes the right amount of chlorine for his pool, as long as his ph is right. I held back my laugh-- He's a pool newbie like me and still trying to learn what he can about pools.

His pool builder told him that the ideal salt level for his pool is 3400 ppm(it also says that on the swgc). And with the indoor controller, if the 3400 ppm drops, you increase the percentage, and if the ppm rises, you decrease the percentage.

I told him that over time, the salt ppm would go down, but I can't see it going up unless you add salt. He said that his salt has gone up to 3500 before so he decreased the percentage and it went down. He also said that when the ppm went to 3200, he raised the percentage and the ppms rose, confirming what the PB said.

How could this happen? Has anyone heard of this before? Can percentage changes to the controller increase/decrease the salt level reading on the indoor panel? My indoor panel's salt level has generally gone down with the rain and evaporation, but has a couple of times increased slightly without me adding salt. I take it that it's equipment error, not due to ph changes or controller percentage changes?

 

[Strannik]

mmm... i'm not familiar with Pentair's equipment so can't say if that's what it really does
but you are right, if salt goes down the only way to bring it up - add more salt

btw salt level is not affected by evaporation as salt doesn't evaporate

 

[tsunami]

btw salt level is not affected by evaporation as salt doesn't evaporate

I wonder why the level dropped from 3500 to 3000 in 2.5 months? I can see the ppm's going down if the water level rises due to rain, but when the level drops back to the normal level, shouldn't it go back to 3500? My water level is still a bit higher from the rain. I'll keep an eye on it as it get's back to the normal level.

 

[Strannik]

if you dilute it - ppm will go down, if you evaporate - goes up.

but salt always stays in your pool, it only gets lost with backwashes, splash outs, rain overflow etc.

 

[mas985]

I wonder why the level dropped from 3500 to 3000 in 2.5 months? I can see the ppm's going down if the water level rises due to rain, but when the level drops back to the normal level, shouldn't it go back to 3500? My water level is still a bit higher from the rain. I'll keep an eye on it as it get's back to the normal level.

If the rain caused the pool to reach an overflow, assuming you have one, salt can be lost that way. It can also be lost through backwash, splash out and worst case a leak.

As for increasing salt level, salt can also be added via the fill water. We have close to 200 ppm in the fill water depending on the time of year.

 

[tsunami]

if you dilute it - ppm will go down, if you evaporate - goes up.

but salt always stays in your pool, it only gets lost with backwashes, splash outs, rain overflow etc.

If the rain caused the pool to reach an overflow, assuming you have one, salt can be lost that way. It can also be lost through backwash, splash out and worst case a leak.

As for increasing salt level, salt can also be added via the fill water. We have close to 200 ppm in the fill water depending on the time of year.

Thanks, I think that's it!

Yes, I do have an overflow, and the water has gotten over that a couple of times now.

I didn't think of the overflow! I bet that, and the splash out from cannonballs are the main culprit of the drop in salt. I haven't back washed at all, just cleaned the filter instead. I did a bucket test with the filler off and no leaks!

 

[JasonLion]

It can take a very long time for FC levels to fall if the water is cold and the CYA level is high. Depending on just how cold it is this winter, you might well be fine till spring. I would leave the SWG on 0% and test the FC level about once a week. When the FC level does finally fall, you should be able to maintain it with a very low percentage setting as long as the water remains cold.

By the by, salt level readings given by the SWG can also vary with water temperature, even when the actual salt level does not change. The kind of salt tester used in a SWG is quite temperature sensitive. Most of the SWGs are "temperature compensated" to some extent, adjusting the reading to be more nearly correct based on their measurement of the temperature, but even then they rarely correct the reading completely.

 

[tsunami]

It can take a very long time for FC levels to fall if the water is cold and the CYA level is high. Depending on just how cold it is this winter, you might well be fine till spring. I would leave the SWG on 0% and test the FC level about once a week. When the FC level does finally fall, you should be able to maintain it with a very low percentage setting as long as the water remains cold.

By the by, salt level readings given by the SWG can also vary with water temperature, even when the actual salt level does not change. The kind of salt tester used in a SWG is quite temperature sensitive. Most of the SWGs are "temperature compensated" to some extent, adjusting the reading to be more nearly correct based on their measurement of the temperature, but even then they rarely correct the reading completely.

Thanks, good info!

The temps have been hovering around 52-54 degrees lately. I've read in the manual that the swcg stops producing chlorine at 52. Since it's not producing at 52 degrees anyway, would it be better to just turn it off completely, or just leave it at 0%? I was wondering if leaving it at 0% would be more taxing on the system, verses turning it off completely?

 

[JasonLion]

0% and off are essentially the same thing.

 

[bk406]

Turning it off will save a bit of electricity.