Shock level of Chlorine vs Slam Level..is there a difference ?

[gdog2004]

Hey guys:
I have some algae in my pool and want to SLAM but am waiting for some rainy days.
My pool is crystal clear but there are spots of Algae. My total chlorine is 4.0 ppm--- and PH is at 7.4 and CYA about 25.
What is the different between SLAM and Shock value ? I have read here that you can swim during SLAM but not shock level but cant seem to fine a chart showing both.

 

[mknauss]

SLAM is Shock Level And Maintain.

TFP shock level is 40% of CYA. It is safe to swim in the pool with that level of FC.

 

[gdog2004]

SLAM is Shock Level And Maintain.

TFP shock level is 40% of CYA. It is safe to swim in the pool with that level of FC.

Thanks for the speedy reply !
I could have swore I read in some old post one of the moderators saying you could swim during SLAM level but not shock level so based on that,
I thought there was a difference. It sounds like they are the exact same levels.
So if my CYA is 25...how do you calculate 40% of that ?

 

[Katodude]

Your CYA is actually 30, we round up since the scale is logarithmic. So your SLAM level is 12.

 

[IceShadow]

Firstly, how did you measure a result of 25? Want to be sure that is an accurate number.

 

[gdog2004]

Firstly, how did you measure a result of 25? Want to be sure that is an accurate number.

filled a tube with pool water up to the line and the rest with the CYA test solution. Shook for 30 seconds. Poured into tube...lowest mark on the tube was 30 with a tiny bit of space after that (about 1/4 inch) . When I filled the entire tube (I could still see dot at 30 but not when the entire tube was filled) I rounded it off.

 

[IceShadow]

OK, so you're somewhere less than 30. Can't really round - if it's under 30, then it's hard to know exactly where your CYA is. If it was barely visible at 30 you can probably round up to 30 and call it that for now.

Might be worth adding about another 10ppm of CYA to be sure you're up where you need to be. If your CYA is too low, your FC will be eaten up by the sun before it can really help your pool.

If it were me, I would raise FC to 12ppm (assuming 30 is the CYA level) but also add another 10ppm of CYA to the pool via the sock method. After 2-3 days I would re-check CYA and if I'm still in SLAM mode, I would re-adjust the FC target if the CYA rose above 30.

 

[gdog2004]

OK, so you're somewhere less than 30. Can't really round - if it's under 30, then it's hard to know exactly where your CYA is. If it was barely visible at 30 you can probably round up to 30 and call it that for now.

Might be worth adding about another 10ppm of CYA to be sure you're up where you need to be. If your CYA is too low, your FC will be eaten up by the sun before it can really help your pool.

If it were me, I would raise FC to 12ppm (assuming 30 is the CYA level) but also add another 10ppm of CYA to the pool via the sock method. After 2-3 days I would re-check CYA and if I'm still in SLAM mode, I would re-adjust the FC target if the CYA rose above 30.

sounds like a plan....I am assuming it is safe to swim if I add all of that ?

 

[IceShadow]

sounds like a plan....I am assuming it is safe to swim if I add all of that ?

To swim safely you need:

- pH somewhere in the 7's
- FC needs to be above minimum and below SLAM level
- Clearly see the bottom of the entire pool

You've got the first one covered. For the second, if you're really concerned, you could stay out of the pool for 2-3 days and then test the CYA (it takes about that long to register on a test). I can't tell on the third as I haven't seen photos and you haven't said if the pool was cloudy, but if it's not, you're good to go. (You can get in a cloudy pool but I would recommend someone outside the pool watch, just in case.)