Chlorine loss during the day

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M

maxwell

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Apr 30, 2013
13
I am a new pool owner and still awaiting my TF-100 Test Kit. For now I am using the Oreq test kit that was provided by PB.

I am concerned about the amount of chlorine loss during the day. My pool gets about 12 hours of sun each day (7 am to 7 pm). Currently I am using just Muriatic Acid and Liquid Chlorine (10%) to pool.

I am adding chlorine in the evening at about sunset. I am testing water two to three times per day for CL and pH. An hour after adding liquid chlorine (about 1/2 gallon) these are my readings:

TA - 90
pH - 7.8
FC - 2.5


Sorry these are the only readings I have with my current test kit.

Testing again in the morning (7 am), chemicals are at the same level (no chlorine loss).

Testing again at 10:30 am, FC is about .6

By the end of the day FC is at O.

Water is and has remained crystal clear.

My concern is why am I losing so much chlorine during the day? Is that strictly from the sun? Is it still safe to swim? Should I add chlorine during the day? Should I be adding more chlorine at night to get the FC level higher?

I know the amount of FC needed is affected by CYA, but I can't test those levels until I get my TF-100. Is it worth going to pool store to get tested or should I just wait for my kit?

Pool was filled June 28, 2013.
 
If this is fresh water and you have added no stabilizer, dichlor or trichlor to the pool (is this true?), then you have no stabilizer and the sun is taking away your chlorine about as fast as you can add it. I would start by getting about 30 ppm cya in there. Use poolcalculator.com to calculate how much you need ( I get 8 lbs of cya will raise you pool by ~30 ppm) and hang it in an old sock in front a return (water flowing back to pool) to dissolve.

Yes, you can, and in your case you should add chlorine during the day so that you do not drop below 1 ppm FC (for 0 cya).
 
If your CYA were 0ppm, then you would lose about 50% of your chlorine in the noon sun.

So if you have 2.5 @ 7AM and assume you lose 50% every hour (even though sun is not as intense). by 8AM you would be at 1.25
9AM 0.63
10AM 0.31
etc

So, what you are reporting just sounds like you need to add some CYA in the water to protect the FC.

Would not hurt to have the pool store test it ... if they show 0ppm (well really they will just be able to say < 20 or 30ppm) then you could likely get a head start by adding 20-30ppm of CYA.

Have you ever added any dichlor / trichlor / stabilizer?
 
PB had two 3" tabs (one in each skimmer basket) 3 days after filling and added two more about two weeks ago. I have been hesitant to add more or use a floater because of the warning about getting CYA too high and needing to drain pool.

No stabilizer. Tabs are trichlor.
 
If goal is to raise CYA, would using trichlor tabs in a floater for awhile be as effective as adding the 8 lbs of CYA in a sock? Is it simply a cost difference? What are pros and cons of using trichlor vs. solid CYA as a method of raising CYA?
 
No because it takes a long time to add it that way since the trichlor pucks take awhile to dissolve...that is unless you put a bunch of pucks in contact with the water...but then your FC would be too high.
 
Do you already have a bucket of pucks? If not, then I would not buy any.
If you do have them, then you could add around 20ppm of CYA using stabilizer and then use the pucks for a little while to slowly continue to raise the CYA. Or you could just save them for when you need a boost to the CYA level or to use for vacations.
 
I do have a bucket of pucks because I anticipated supplementing my liquid chlorine. That was until I learned about too much CYA. I think I will buy solid CYA to bring it up and leave a cushion because I will be going on vacation in September and will need to use pucks during that time.

Is it unsafe to let kids swim at 0 FC. I can add during the day, but I feel like it will drop almost as fast as I add it. If it is okay, I will continue to add at night and go to Leslie's now to test CYA and buy some solid CYA to start tonight. Will I need to run filter 24 hrs a day until solid CYA is fully dissolved?
 
We say it is safe to swim with the FC > the minimum and < the shock level for your CYA. We would not say it is safe to swim when the FC is zero as there would be no protection from person-to-person transmission.

Get 20-30ppm of [s:13ntt0ht]FC[/s:13ntt0ht] CYA in the pool and then maintain FC > 2ppm.
 

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Do I really need to Shock the pool? According to the pool calculator, that is 5 gallons of 10%. If I have done an OCLT and passed this seems unnecessary.

If I raise the CYA, then I should be able to maintain my FC throughout the day and all is well right?
 
I don't think anyone suggested that you need to shock your pool. If you are referring to jbliz's response on safe to swim levels...he is just saying that you can safely swim up to your shock level. Get some chlorine in there to get up to at least 2 ppm FC.

How does you water look?
 
Who said you needed to SLAM the pool? {We do not use the "shock" word as I think you are}
If you pass the 3 criteria, then you should not need the SLAM process.

I would:
-Get the CYA up to ~30ppm
-Raise the FC toward shock level
-Perform the OCLT to verify nothing is in the water ... if the water is clear, and you have no CC, then this would confirm your pool is clean.
 
I'm just not sure why to raise FC to shock level. 20-30 ppm. According to "The Pool Calculator" that is 5 gallons of liquid chlorine (10%).

If I get the the CYA up to 30 ppm, can't I just maintain FC at 4 ppm?
 
Are you looking at the chart? pool-school/chlorine_cya_chart_shock

If your CYA was 30ppm, then shock level is 12ppm. I would suggest raising the FC up to around 10ppm or so and then doing the OCLT. I just like to do the OCLT more at the higher FC levels as I think it is a better test. And you would still be below shock level and safe to swim.

If it were my pool and I knew the FC kept dropping to 0ppm ... I would want to verify nothing was in the water by performing the OCLT and then the SLAM process if required.

But, if you are 100% confident that there is nothing in your water .... then just maintain normal FC levels.
 
Re: Chlorine loss during the day (Update)

Water Analysis According to Leslie's

FC - 2.0
CC - 0
CH - 160
CYA - 0
TA - 100
pH - 8.0

Action: Adding 8 lbs CYA granules. Directions say to mix 4lbs in bucket of warm water and to poor into skimmer.

Jblizzle and Linen predicted that was the case.

Linen suggested a sock and hang in front of the return. Should I follow the directions on the package or use Linen's method?

Either way, I will run filter for 24 hrs.
 
Okay cool.

I like the idea of raising FC for OCLT. I will try that.

I tried last night at about 3 or 4 ppm and passed, but 10 ppm won't hurt. I'll give it a shot.

If the sock is touching the side of the pool it won't cause any staining will it?

Thanks everybody for your input.
 
Ideally you do not want the sock touching the side ...it could bleach the liner.

I have seen people hang the sock on a pole and suspend that in front of the jet.
You can give it a couple squeezes every so often to help it dissolve.
 

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