High Chlorine LEvels

[tjt040774]

Took my water to a nearby pool store on Saturday. First off, the sample was about 3 hours old when it was tested, so I don't know what effects that had. My numbers were as follows:

FC 8.0 ppm
TC 8.0 ppm
CC 0.00
PH 7.4 ppm
Hardness 165 ppm
Alk 115 ppm
CYA 50 ppm
Copper 0.0
Iron 0.0

My question is how to lower my chlorine level. The pool was built in July and had the SWG on 100% up until say October, when the pool builder dropped it to 65%. The pool store recommended dropping it to 40%, but I went to 35%. I just checked it with my test strips, and it is still high. I would give a number, but am clearly having trouble reading that particular color (green) and associating it with a number. Live in southeast Texas where the temps are currently ranging between lows in the 40's and high's in the 70's. Thanks for any help...

Travis

 

[zea3]

According to the Pool calculator, your chlorine level should be between 2 and 8 to properly sanitize the water. One of the guys with a swg pool can advise you better. All you need to do to lower chlorine is to back off the % and let the chlorine fall naturally. It will fall more slowly in cooler water. Also you don't want to let the chlorine drop below minimum level which for you is 2 ppm.

 

[tjt040774]

Should I turn the SWG off all together until the chlorine level comes down some?

 

[PaulR]

As long as you're testing often enough to catch it before FC drops too far, turning the SWG off should be okay.

Also, upgrading from the strips to a "real" test kit would help you in the long run. Check out the test kit article in Pool School.
--paulr

 

[Brentr]

Correct me if I am wrong, but what is wrong with and FC of 8???
Unless you are swimming I would let it naturally fall and back off on the SWG and monitor it. Use a good test kit, I use the TF-100. That way you can get to know your pool

 

[polyvue]

Correct me if I am wrong, but what is wrong with and FC of 8???
Unless you are swimming I would let it naturally fall and back off on the SWG and monitor it.

In this case, I think it's a more a matter of what you feel comfortable with... 8 ppm Free Chlorine (coupled with CYA at 50 ppm) is providing a lot of disinfection and oxidation. If it's not being used up, due to low level of contaminants, lack of sun light or low bather load, that's fine. But those SWGs are persistent things -- they'll keep making hypochlorous acid whether you need it or not!

An industry maxim suggests that the optimum level of free chlorine is 1 - 2 ppm. This forum suggests 3 - 5 ppm FC for SWG pools, but it must be taken in context: the suggested level of stablizer/conditioner level (CYA) is 70 - 80 ppm. Using the 5% rule (of thumb) we can deduce a minimum Free Chlorine level. 70 * .05 = 3.5 ppm. More than this is certainly appropriate if there is significant chlorine demand (ie., it gets used up in a short time); and higher levels (up to 8, anyway) probably* won't do any long term damage to equipment or plaster.

Protected by a rubric that may have been invented just to annoy people who like rules and uniformity ("every pool is different") I maintain a lower than recommended CYA level (40-50ppm) and target a chlorine level of 3.5 ppm. At this time of year I have to add liquid chlorine once in a while to maintain this level. During the summer, the SWG would be shocking the pool 24/7 if I let it, so I'm always fighting to keep FC in check. Tip: When your SWG controller starts speaking to you in a low, melodious voice... suit up, approach the cell from the dark side, cut the power that controls the electrolysis and higher memory functions. Ignore repeated queries regarding your mission.


* This means that I'm guessing.

 

[tjt040774]

Just as an addendum to my original message, when I took the water in the lady testing it actually said that my chlorine was "off the chart." So I'm not sure if she meant that 8 ppm was "off the chart" or the chlorine levels were literally off the chart and 8.0 is as high as they can measure. I lowered my cell to 25% production today. I'll wait a few days and see... So, all that being said, I appreciate the input and hope that it continues. Thanks.

Travis

 

[polyvue]

Just as an addendum to my original message, when I took the water in the lady testing it actually said that my chlorine was "off the chart." So I'm not sure if she meant that 8 ppm was "off the chart" or the chlorine levels were literally off the chart and 8.0 is as high as they can measure. I lowered my cell to 25% production today. I'll wait a few days and see...

Travis, good catch! I'm glad you addended 'cuz having chlorine at an undetermined high level (could be 8... 18... 28 ppm?) justifies a higher level of concern than if it were just 8 ppm. What do your test strips indicate? Do they measure chlorine past 8 ppm?

In this case there's no question that you would benefit from using a FAS-DPD chlorine test to corroborate the pool store's opinion (that the chlorine is "off the charts") and to assist you in determining what course of action to take, if any. And turn off that SWG -- at least until you're able to get an accurate measure of the chlorine. Both of the following mini-kits will do the job and cost less than $25, excluding shipping.

http://www.taylortechnologies.com/produ ... KitID=2185
http://www.tftestkits.net/index.php?act ... oductId=24

Act today. Don't make us send you to the woodshed!

 

[PaulR]

Travis, did you happen to notice what kind of test the pool store did? Test strip in a computer; or putting in drops to make the sample turn yellow, or pink; or make it turn pink and then put in drops to make the pink go away? If you didn't notice, that's fine. Some of the more common (and cheap) chlorine tests have you compare a colored sample to a standard, and those usually only go up to 5ppm. In that case saying 8 is just a guess.
--paulr

 

[Melt In The Sun]

Some of the more common (and cheap) chlorine tests have you compare a colored sample to a standard, and those usually only go up to 5ppm. In that case saying 8 is just a guess.
--paulr

Definitely true; the first time I tested my water, I guessed about 7 ppm since the color was very slightly darker than the "5" block. It was actually about 25! Once it's off the scale, it's completely worthless.

 

[tjt040774]

I turned the SWG completely off this morning. I just tested the water when I got home from work and the best I can tell, I'm at about 10. Now, 10 is the highest my test strips will read, but the color seems to match. So I guess I just leave the SWG off and test every day until it drops to a reasonable level? Tell me if I'm wrong. We did get a heavy rain last night, so I know that I lost some pool water to overflow. Thinking that will also help to drop the level.

Travis