4 Day Vacation = Algae

[YippeeSkippy]

Yes -- I wish the instructions said to add drops until the color does not change like their video.
Odd...my TF-100 test kit does I believe?

If the powder injects a ton of active chlorine, why is the powder/liquid shock (e.g. non bleach) not a valid option? And, why do you specifically mention SWG and powder shock? I am going to shut off SWG during SLAM to ensure I can completely control FC levels. I got jugs of 6% bleach at Walmart so I am armed but just trying to fill in the missing pieces.

Powdered chlorine also contains either unnecessary calcium or more CYA. Most pools need neither


1) If daily FC/PH via TF-100 test kit is performed, why is the FC test even performed if CYA isn't also tested at the same time? Or is the assumption that CYA .is already known (from weekly test) and a bit outdated but that's acceptable?
FC is a consumable ingredient.... used up by bather sweat, pee, lotions...and of course the sun's rays. So one needs to monitor its level daily or every other day to keep it boosted up when necessary. CYA is longer lasting, only breaks down slowly. You can test it one week and it will be the same the next.

2) My pool is 32K gallons per pool inspection but even if accurate, water level changes so how can you even get the SLAM FC level accurate? Is there a range?
Testing gives you current results. You don't base your treatment level on tests that were done prior to water exchanges.

3) Is there a calculator to know how much bleach to add to maintain SLAM FC level?
PoolMath PoolMath

4) After SLAM is completed via overnight test, I will still have high FC. You said it is OK as long as it is inline with CYA but that still means we are swimming with high chlorine which isn't something I am comfortable with. Since FC/CYA are aligned, how can the FC ever go back down to normal levels?
Because the CYA "buffers" the FC. FC at 2ppm with *no* CYA is far stronger than FC at 10ppm with CYA.

4) The Chlorine/CYA chart for SWG (Chlorine / CYA Chart - Trouble Free Pool) only has metrics for 70-80 as 60 has * for 'not recommended'. That's a very narrow window of CYA to maintain. Is that correct?

The way SWGs work it has been found that having enough CYA protects yet isn't too much.

 

[sagosto]

I need to re-check the CYA. I am using an example. A CYA of 70 and a current FC of 5 requires 13 jugs of bleach to get to 28 SLAM FC for the 1st SLAM. That simply cannot be true... My local Walmart did not have 12 jugs of bleach.

 

[Mr Bruce]

6% is kind of weak. WalMart (usually) has 10% in the pool section. That would be slightly less than 8 bottles.

We have big pools

 

[jblizzle]

You have a big pool therefore you need lots of chemicals you only will need 12 bottles for the initial dose as you continue to test and add additional chlorine it will be much fewer bottles

I can't currently see your signature, what size swg do you have? It very well may be under sized for your pool

 

[sagosto]

If lower CYA requires less FC, then why not keep CYA nearly as low as possible or even 0? I thought CYA protect Chlorine? I am really missing something.

I am also very concerned about the need for 12 jugs in the above scenario...

 

[Mr Bruce]

It sounds like you are having a hard time wrapping your head around the FC/CYA relationship. Here's a good thread if you care to look into it more. Chlorine/CYA relationship see especially post 11.

 

[sagosto]

I bought the plain jugs of bleach in the laundry section. The pool section has 'shock' labeled stuff such a powder. Even if it is high %, there certainly isn't 10 or so jugs of this stuff on the shelves.

 

[mknauss]

This might help.

 

[sagosto]

After FC hits 28ish and algae is gone, how long to wait before pool can be used. Won’t it take a while for 28 to reduce to target 5 range?

 

[mknauss]

You can safely swim in a pool as long as the FC is above the minimum and at or below SLAM level based on your CYA. You must also be able to see the bottom of the pool in the deep end of the pool.

 

[Mr Bruce]

It is safe to swim up to and including SLAM level.

 

[JoeSelf]

Its ONLY 28 if your CYA is 70. FC 28 @ CYA 70 is less harsh than 1 FC & 0 CYA. CYA buffers the chlorine. Use what number you measure with your kit and look up the SLAM level for that number.

Full sun at your back, fingers at top of tube, held waist high. Fill to lines and glance into tube. If you see the dot, fill to next line and glance in again. Do this until dot disappears. Don't stare it wont go away.

 

[markayash]

I was gone a week and I had some yellow algae on the walls but brushed off..My chlorine is still normal so hopefully I am good..WE also have mid 90's but no rain in Atlanta, pool was down below tile but to be safe I had turned the skimmers off and just pulled from middle drain before I left! Learned that last year when I came home to a gurgling pump

 

[sagosto]

Its ONLY 28 if your CYA is 70. FC 28 @ CYA 70 is less harsh than 1 FC & 0 CYA. CYA buffers the chlorine. Use what number you measure with your kit and look up the SLAM level for that number.

Full sun at your back, fingers at top of tube, held waist high. Fill to lines and glance into tube. If you see the dot, fill to next line and glance in again. Do this until dot disappears. Don't stare it wont go away.

This makes sense but if the FC is aligned to CYA, how can you really tell you have a bit high chlorine or VERY high chlorine meaning the pool shouldn't be touched? To the common folk FC @ 28 sounds crazy especially when a lot of literature says 2-4PPM is adequate.

The black dot has white around it. Do I keep looking till I can't see *ANY* black at all? I suck at CYA reading because there can be a 50 swing between a light shade of black and NOTHING at all. Do you use the white outer rim of the black dot at all?

 

[mknauss]

When you do the CYA test, try this next time.

Once you have your solution ready, back to the sun, etc. Fill the vial to a line, say 80, lower the vial to your waist level and glance for the dot, you see it, add solution to the 70 line, glance, see it, repeat until you no longer see it with a glance. Then use the CYA value one step above the line you read. So if you stopped at 50, use 60 ppm CYA.

The vial is in logarithmic scale. So it is not viable to interpolate between the lines. Just use the whole numbers, such as 50, 40, 30, ....

 

[Mr Bruce]

From the thread I linked earlier:

As for your worry about your kids swimming in a pool with high FC, again the FC number by itself is irrelevant towards chlorine's actual effects when CYA is present. My wife has personally experienced this difference when she has swum in an indoor commercial pool with 1-2 ppm FC and no CYA and her swimsuits would degrade (elasticity gets shot) in just one winter season of swimming and her skin was flakier and hair frizzier. In our own outdoor residential pool with 3-6 ppm FC and 40 ppm CYA, her swimsuits would last for 7 years and the effects on her skin and hair were substantially less noticeable.

Let's say one has 70 CYA. If you have a FAS-DPD test, anything from 5-28 for FC is fine. Anything over 10 in normal (non-SLAM) situations is a little wasteful. That's it.
Here are the extended CYA test instructions. They include a link to the Taylor provided example of what "disappeared" is.

 

[jblizzle]

Still not sure what you are asking about the FC. The CYA buffers it and lowers the active chlorine levels.
We have repeatedly stated that it is safe to swim up to the SLAM/shock level that is listed for your CYA in the FC/CYA Levels.
For any CYA level, the SLAM/shock level FC listed in the table has a LOWER active chlorine level than an indoor public pool with 0 CYA and a FC of 1ppm.
I guarantee that you can swim at a FC of 28ppm if you CYA is 70ppm and not even know it is that high.

Check out this table that shows the active chlorine levels as a function of CYA and FC:
http://troublefreepool.com/~richardfalk/pool/HOCl.htm

The old 2-4ppm is assuming a 0 CYA level based on drinking water standards. The pool industry is still ignoring the FC/CYA relationship that has been know since 1973.

 

[JoeSelf]

You need to know your CYA. That is how you tell your FC level from the chart. The dot should be obscured. Its not a perfect test +-10 accuracy.

2-4 is with no CYA in the literature. 2-4 is not adequate with higher CYA, that is why you have algae.

And we are not NORMAL people!!!!!!

 

[IceShadow]

Also - just for reference, "Liquid shock" is bleach, just at a higher concentration, like 10-12.5% instead of 6%.

 

[sagosto]

CYA exists in the system so that's not a concern. 2-4PPM reference was other literature I've read which is explained that a lot of info that doesn't explain the linkage between FC and CYA. I am good now except not comfortable with 13 bottles of bleach But, I'll re-check my CYA today.