Continue to SLAM?

[Junta]

I'm back. Some of you may have seen my previous post. I am having a heck of a time beating back an algae bloom. Or at least what my testing is telling me is one. I SLAMed for just over 8 days. Then I finally got a zero change in the OCLT test yesterday morning. I figured I'm done. Because I had some inconsistent test results during the SLAM process, someone suggested to wait until my pool got down to about 10 ppm and do another OCLT. I figured I had a couple of days until that happened but figured I test just this afternoon just to be on the safe side. I tested at 5:30 this evening and my chlorine dropped from 21.0 yesterday morning (around 6:30 AM, after sunrise but no sun hits my pool that early) to 12.0 today. That seems like an awful lot to me over a day and a half. Is it? It was sunny and quite warm yesterday. Meanwhile my water is crystal clear (its never not been crystal clear), my CC reading is zero (never been above 0.5), I have pulled my steps and cleaned those (as far as I could tell there was no visible algae on those) and vacuumed yet again. I am planning on doing another OCLT tonight to see what the result is. Should I just start to SLAM again? Thanks.

 

[Texas Splash]

That seems like an awful lot to me over a day and a half. Is it?

Don't let that worry you just yet. The FC will fall quickly once you stop maintaining the FC level like you did during the SLAM. The true test if there is anything to worry about is the Overnight Chlorine Loss Test.

 

[Texas Splash]

On a related note, once your FC level falls back down closer to the regular target zone, if you ever see the FC fall more than about 4 ppm in 24 hrs with no large pool party or anything, then you might have reason for concern and do an Overnight Chlorine Loss Test.

 

[Junta]

Ok. Thanks for the peace of mind! I’ve done so well with my pool over the years,mainly from info on this site, that when things go wrong, I have limited experience dealing with them. Glad these forums exist.

 

[Junta]

I think I may have figured out the source of my test inconsistencies. While during my SLAM period, I was running low on the R-0870 DPD powder. I’m pretty sure some of my measurements where less than a heaping amount as the instructions specify. Last night I tested my chlorine and got 10.5. This morning my first test was 9.5. I tested a second time and got 12. Because of the difference I did a third test and got 12 again. The only difference I noticed was the amount of DPD powder. I made sure it was a healing amount for tests two and three. Add to that I had three different people doing the same test and I’m sure it was a little different for all three of us. Last question….how important is the amount of DPD powder? Is it better to have to much versus too little? Thanks.

 

[Texas Splash]

how important is the amount of DPD powder?

Normally it's not critical. Observing the color change when you first add it is most important. While 2 (level) scoops isn't required like for tests using a 25 ml water sample size, a generous or heaping amount should be fine for the smaller 10 ml sample. Anything more would just be wasteful.