My neighbor was able to lend me some DPD powder R-0870 so this weekend I am going to SLAM it via the process below. Have about 20 gallons of bleach on reserve. When doing the FC test, should I be using the 10mL or 25mL amounts of water as there are 2 different ppm figures per drop.
SLAM - Shock Level And
Maintain
SLAMing your pool is the best way to eliminate algae, sanitize your pool and get your water crystal clear.
If you have algae, or the CC level is above 0.5, or the free chlorine (FC) level is zero, you should SLAM
the pool. You cannot do this overnight...it often takes several days to see it completed...no shortcuts. If
you are maintaining proper FC levels there is no need to SLAM (or shock) weekly, or on any other regular
schedule.
Without adding any stabilizer, add enough bleach to increase FC to "10". Confirm you got
that high then retest 10 minutes later. If it stayed at 5 or above, see the SLAM statement
below. If the FC dropped drastically after 10 minutes below an FC of 5, then increase
immediately and retest 10 min later. Continue this process until the FC holds to at least 5-
10 after 10 minutes time. Once it does, see the SLAM statement below.
(SLAM) - After completing that crazy 10-min FC testing drill, your water is ready to
"maintain" a regular SLAM. Now you add stabilizer as required to get the CYA to a target of
"30". Make sure the pH is at about 7.2, then increase FC to your new SLAM/shock level of
"12" and maintain it that way until you pass all 3 SLAM criteria (link below in my sig).
Remember for FC testing ....
For FC testing, simply use the 10ML water sample with one heaping scoop of powder & mix. Count drops
until clear and divide by 2. Example: 20 drops = FC of 10.
Prerequisites:
You need to have a FAS-DPD chlorine test
You also need to know your current CYA level, and then look up the corresponding FC
shock level. You can use the The Chlorine/CYA Chart at Pool School to find the correct FC
shock level for your CYA level.
CYA (Stabilizer) Minimum FC Target FC Shock FC
20* 2 3-5 10
30 2 4-6 12
40 3 5-7 16
50 4 6-8 20
60 5 7-9 24
70* 5 8-10 28
80* 6 9-11 31
90* 7 10-12 35
100* 8 11-13 39
It is best to use bleach or liquid chlorine when SLAMing. You will want to have enough on
hand to raise the FC level to shock level at least a couple of times. It is especially important
to avoid using dichlor when SLAMing, as it will raise CYA far too quickly.
Make sure the pool is free of leaves and other debris (at least as much as possible).
Make sure your filter is working properly and you understand how to clean it out should it
become necessary.
Check and adjust the PH to between 7.2 and 7.5. The PH test isn't reliable during SLAMing
so make sure to take care of this before you start.
Run the pump 24/7 until you are done SLAMing
SLAM:
Test the FC level and add enough chlorine to bring FC up to shock level (see here for
correct shock level)
Test and adjust chlorine levels as frequently as practical, but not more than once per hour,
and not less than twice a day. Chlorine additions should be frequent, especially at the
beginning. Algae and other organic debris will consume chlorine very rapidly at first. As
things progress, you will lose less chlorine each cycle and can add chlorine less frequently.
Brush and/or vacuum the entire pool once a day
Backwash or clean the filter as needed
Vacuum up debris as needed
You are done when:
CC is 0.5 or lower;
You pass an OCLT (ie overnight FC loss test shows a loss of 1.0 ppm or less);
And the water is clear.
When all three are true, you are done SLAMing and can allow the FC to drift down to
normal levels.