need a little help no cya & low fc

[Jd-underdog]

woke up this morning to a cloudy pool, and tested the water and here is what I found
fc 1
cc 2
ph 7.8
ta 180
cya 0

pool is 40,000 gallons. I added 5 gallons of liquid shock early this am, its still show 1 or less on the fc last week my cya was around 50. where did it go? also i am going to add more stabilizer when i get home tonight, do i need to keep adding shock or wait until the cya level comes up
thanks for your help
John

 

[Texas Splash]

John, just to confirm ... was there any significant water exchange from last to this week that may explain the CYA loss? Also, please confirm what test kit you are using. Thank you.

 

[Jd-underdog]

I did add a little water from the hose to top it off maybe 2" of fresh water. I am using the test kit that i bought here, I have just never seen cya completly dissapear like this!

 

[Texas Splash]

Then please follow these direction before you do anything else:
1. Begin a SLAM and dose FC up to SLAM level. Do not add additional CYA at this point.
2. Retest FC at 10-minute intervals.
a. If FC loss is greater than 50%, add FC to bring back up to SLAM level and continue retesting FC @ 10-minute intervals.
b. IF FC loss is 50% or less, add FC to bring back up to SLAM level. Go to Step 3.
3. If CYA is below 30 ppm, add enough CYA to bring level up to 30 ppm.
4. Continue SLAM as directed in the SLAM article until the SLAM Criteria of Done are met. Test as directed in the SLAM article - no longer need to test FC at 10 minute increments at this point.

There's a method to our madness sometimes.

 

[Jd-underdog]

I did a slam last year, what level do i need to bring the fc up to for the slam? where can I find that article on slam

 

[Texas Splash]

Here you go:
Pool School - Chlorine / CYA Chart (use a shock FC of 10)
Pool School - SLAM - Shock Level And Maintain

Also in my signature.

 

[Jd-underdog]

so i should use the pool calculator and add liquid shock to get the level up to 10 , then test it again after 10 minutes? and just keep doing that? until it loses less than 50%

 

[Texas Splash]

That's correct. Use Poolmath calculator to go from zero FC to 10 (I figured it should be about 256 oz, or right at 2 gallons.) Follow those instructions above. The trick here is to ensure (before you add any stabilizer/CYA) to eliminate any potential items that may be tearing-up your FC at an extraordinarily fast rate. So the 10 min rule is crucial until you know for sure the FC drops are slowing down. Once you get past the 10-minute checks and can hold FC to at least 50%, you can continue with adding stabilizer (target CYA 30) and proceed with a regular SLAM.

 

[Jd-underdog]

is it ok do add the chlorine during the day with it being sunny?

 

[Texas Splash]

If you are home and able to stay there and check every 10 min, yes. The sun won't be eating it up that quick, We're looking for something else chemically.

 

[Jd-underdog]

ok I wonder how much chlorine i am going to need, I think i have 16 gallons on hand

 

[Texas Splash]

Re: need a little help no cya & low fc

I would think (hope) that's enough to at least get started and run through your 10-minute checks. But once you complete that and roll into the regular SLAM, you may need to make another run to the store. You'll have a good idea once you start to see the FC consumption rate.

- - - Updated - - -

Also make sure you have stabilizer on-hand and ready to put in there as soon as you finish the 10-minute checks so you can shot for that target CYA of 30.

 

[Jd-underdog]

ok will do, will the pool calculator figure out how much cya i will need to add? and I assume I should use the sock method for it?

 

[Texas Splash]

That's correct JD. I tried it and came-up with 80 oz (5 lbs) of stabilizer, but you should double-check. Sock method works great hanging near a return jet.