OCLT..to determine if slam is necessary

[Dave C In Ontario]

Is it safe to say, if I pass a OCLT that I don't need to SLAM.
I've read a lot of threads about all sorts of issues.. cloudy water..etc.
Many times the response to the OP will be to SLAM.. is it safe to always just do a OCLT first.. and if passed, no SLAM is required?

 

[ccbill]

Three criteria to Not SLAM,
Pass OCLT
Combined chlorine (CC) <0.5
Clear water

OCLT is pretty easy to do, start there and test the CC while you are at it.

If the OCLT is good but CC is high then you don't have an active algae problem but you need to SLAM to oxidize the chloramines - but that shouldn't take long at SLAM levels.

 

[Oly]

Have you passed an Overnight Chlorine Loss Test and are observing cloudy water?
Are you testing FC with a FAS-DPD test? Testing CC?

 

[Dave C In Ontario]

Sorry, this was more a learning post..
I don't really understand if your water is cloudy.. how would your pool pass an OCLT test..assuming algae is the cause of the cloudiness..
If algae is not the cause then does a SLAM fix other issues that cause cloudiness?
I am just trying to understand the process
Thanks for the replies!

I guess I should ask..
New pool, water beginning of summer..
My logs should be visible..
I tested daily using k2006C .
My target fc was 6... and I tried to never go below 4 ..might have hit 3.5 once or twice.
Water was clear no problems.
PH was steady 7.6 all year until late aug where it started to constantly climb.
Cc .2 all summer
Only used pucks until cya got to 50.
Ch 100 to 110 all summer
TA was 70 .. has fallen to 60 with me using PH down in Aug/Sept trying to keep PH below 8.
Used liquid chlorine all summer.
SWG finally powered up last week.
I live in a cold climate so water temperature is 62 now.. and looking to close in the next 10 days..
I haven't SLAM'd yet..ever..
Should I have??.. or better question should I before closing.. or just raise it a bit and then pit the poly60 in?
I "feel" the water isn't quite as clear as the beginning of the summer.. but it would be hard to say it wasn't..

 

[Texas Splash]

Is it safe to say, if I pass a OCLT that I don't need to SLAM.

In most cases that is correct. One exception could be Mustard Algae (MA). We first pass all 3 regular SLAM criteria before increasing the FC to a higher % rate for 24 hrs to ensure all MA spores are eliminated. If not, then the MA can return. We are also very careful about each scenario posted here at TFP since some owners may think they passed their OCLT, when in reality there was a testing error or some other issue that provided a false pass result.

Do you ever need to SLAM just to do it? Not unless there is a need to. Closing could be one example of a good time to increase the FC to SLAM level. It is very common and a typical practice for many who close for the winter. If you do though, and plan on using Poly 60, increase the FC soon enough (about a week prior) so that it can fall a bit first. If you add the Poly with a SLAM FC level the Poly (or some of it) will get eliminated. Some take it to SLAM level and skip the Poly, that's a personal choice based on local experience with their pool.