chlorine 'stuggles'

[eqbob]

So I guess this is the good/better kind of chlorine problem to have in that I've been having way too much. I have repeatedly dialed down the salt cell from its summer running of 60% and as water temps drop and nobody's you swimming and massively different solar load, the chlorine kept rising, even as I was dialing SWG back.

So abut 4 days ago I dialed it back to 10% and it (FC) seems to have stabilized right now at about 6ppm. With 0 ppm CC.

So I will continue to watch it. Obviously don't want it to get too low (it was north of 16 a few weeks ago), but not like anything is going to grow in 63 degree water even if it gets a lot lower..and that Bering sea storm is supposed to drop is 20-30 degrees by mid-week.

Any thoughts or comments?

 

[Killer95Stang]

I'm right there with you. I had my swg down to 15% and forgot turn the easy touch back to normal from service mode, which meant no pump for almost two days. As soon as I noticed I ran test and still found my FC and TC at 8.5. This is with water above 70 degrees. I'll probably turn down to 10% when the water gets to the mid 60s and dial back the run time a little.

 

[pwrstrk]

eqbob, there isn't any guarantee that nothing is going to grow in 63 degree water so make sure you keep your FC in range. Yes algae has a harder time starting as the water temp gets colder but that doesn't mean you can't have something start growing.
You'll hold FC in longer colder water, but still keep it in range at all times.
Just wanted to give you a heads up. ?

 

[eqbob]

Killer-good to know this isn't some weirdness I alone am seeing...

Jeff-thanks for the heads up and reminder to be vigilant on it... I will continue testing. I can easily turn it back up some and get more production if needed. Appreciate it.

 

[Patrick_B]

Good plan, and no its not surprising. Good situation to have, but make sure it doesn't go the other way. Once the water cools way down algae will grow less, but your SWG will put out less, and eventually none if you get too, or close to 50 degree water.

 

[eqbob]

Yes. Once it gets to 50 I will plan on using bleach since the salt cell will turn off. This is the first time I've done that however, so I'm real sure how often I need to add, what levels to keep it at, etc. I have to find the references of what type of bleach to use, what strength, etc... I don't want to use pellets aince that will just elevate the CYA levels and then in the spring Id have to drain and fill as I understand it.

- - - Updated - - -

I also have to figure out how to adjust the run time of the pump using my Pentair box. I could always turn the run time down from 12 hours as well.... That is if I could figure out where in the menu structure to control that....

 

[eqbob]

I would think it would be helpful to know the 'exact' chlorine out out of the SWG at different levels. Is there a formula for this, or known for different cells? I'm not sure how you would get that information by testing because you wouldn't know your loss rate.

 

[chem geek]

The output from the SWG should be directly proportional to the % on-time setting times the pump run time. The 100% output should be given by the manufacturer based on model. You didn't list the manufacturer and model of your SWG, but if I guess that it is a Pentair Intellichlor then according to this manual the IC15 outputs 0.60 pounds Cl₂ per 24 hours, IC20 outputs 0.70 pounds Cl₂ per 24 hours, the IC40 outputs 1.40 pound Cl₂ per 24 hours, and the IC60 outputs 2.00 pounds Cl₂ per 24 hours. So take this amount, divide by 24 hours, multiply by the number of hours of pump run time, and multiply by the % on-time. This gives you pounds of chlorine per day which you can put into PoolMath to figure out FC by using "chlorine gas" in the Effects of Adding Chemicals section near the bottom of the page.

 

[Sandra B]

I'm having this same "problem"! My SWG is set around 40% for 12 hrs/day/summer, and I found that it kept going up even as I lowered the %. I put in a new salt cell last fall and the new one is a lot more efficient than the 6 yr old cell I replaced, so I don't have my percentages dialed in for cold water yet. I was up to 14 FC even while lowering the %, from a normal of around 7. I finally put it to 0% a couple days ago so I'm eager to see what I have tomorrow (I waited a couple days to test to let it go down). My water temp is around 65 degrees.

Chem geek, how does the temperature affect the chlorine output, per your formula? I'm thinking there's no linear move downward, since it depends not only on your water temperature but also CYA and sunlight/location. Is there a shorthand for temperature only? Like for every 10 degrees down in water temp, the SWG produces xx% less chlorine?

 

[eqbob]

Very interesting. Thank you Richard.

So it's an IC40, so 1.4 / 24 hours = pounds per hour x 12 hours run time = pounds total at 100% x 10% = 0.07 pounds = 1.12 ounces which pool math says raises chlorine by 0.7 ppm

So given that I can track where my chlorine usage is and then adjust salt cell percentage to equal that.

Kewlmess!

 

[chem geek]

Sandra, the formula I gave is for the SWG output, but what happens to the FC level depends on the chlorine usage and that drops significantly with less sunlight and with lower temperature. Roughly speaking, the chlorine loss due to temperature drops in half with every 13ºF drop in temp while the chlorine loss from sunlight drops based on the angle of sunlight and number of sunny days (i.e. cloudy days have less UV). I suggest you just turn off the SWG and measure the chlorine loss and then set the SWG to output roughly that amount of FC. eqbob has it correct.

 

[eqbob]

Well, I overshot. Measured this morning and FC was at 1.8 and CC was at 0. Obviously too low, so kicked SWG percentage backed up to 25 and also put it on superchlor for a 4-hour cycle which should dump another 2.3 ppm in there. Can always run it again this afternoon to get more or drop in some bleach. Water at 63.

 

[pwrstrk]

I don't have an SWG, but from what I've read on the forum, some of it is a trail and error thing to you get set right. I'm sure you'll get it figured out. Like you said and it's the right thing to do, is bump it up with some bleach if need be. ?

 

[pooladdict]

I wouldn't recommended superchlor, you are shortening the life span of the cell. Far cheaper to use some liquid bleach.

I would think at 63 degrees your chlorine demand has really dropped. I am not sure you would require the same ppm versus water being 75.

 

[eqbob]

The superchlor was available immediately, whereas the bleach was not since I don't have any and have to figure out what to buy.

I know it stresses the cell more, but on a lifespan of approx 5 years, running something at 100% for a few hours isn't going to really significantly affect it... Unless there is a huge non-linear degradation curve.

- - - Updated - - -

I would also agree demand has dropped with much colder water and different sunlight demands. But I'd like it to be in the 4-5 range on a regular basis. I'm looking for consistency and knowing what my SWG will do at what percentage to keep it stable. When it goes off, I will then use the bleach. But that's a whole 'nother learning curve... How much how often.

 

[pwrstrk]

Pool Math will tell you how much bleach to add and testing every so often will tell you when.
You can bring your FC up to shock level with bleach for your CYA level and with cold water it will lose FC slowly.
If your not going to use the pool, a cover will help loads in holding FC. I bring my pool to shock level for the winter and it'll hold FC for 4-5 months. When I opened this year in March I had 4 ppm of FC. ?

 

[eqbob]

I thought about a cover but I sure do like looking at the pool. Cost wise it isn't in the cards right now. We are still getting one of our dogs back to walking normally and were about 15k on that one.

I will look at pool math. The bleach is unscented and the highest percentage you can find, right?

 

[pwrstrk]

Right, just regular household bleach. No scents, splashless anything like that. Get Walmart's brand. It'll be 8.25 %. That's what I use. ?

 

[eqbob]

Right, just regular household bleach. No scents, splashless anything like that. Get Walmart's brand. It'll be 8.25 %. That's what I use. ��

Great...thanks!

 

[eqbob]

Richard,

How close is the chlorine gas vs SWG cell on that bottom line? Should the rise in FC be an expectation or an approximation? Reason for asking is at 8am I did the superchlor for 4 hours with FC at 1.8 which should have added 2.2. At 2:30 I tested again and FC was at 3.. So definitely better, but not to the 4 that would be addative. However that calculation doesn't account for loss and it is bright and sunny today, so maybe it all makes sense...