Annual early-May SLAM... I want to fill this thing in with sand.

wgipe

Gold Supporter
Jul 4, 2020
515
Fletcher, OH
Pool Size
20000
Surface
Vinyl
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
Welp. Here we are again. First week of May, and I'm back in a SLAM because the pool started losing chlorine slowly after heating it. Every. Single. Year. For 3 years. It's fine when opening, I start to heat it, and I end up in a 15-day SLAM, using 40 gallons of chlorine, requiring tons of work, and making me fantasize about filling this stupid hole with sand instead of water. Once the SLAM is through, the SWCG holds chlorine at a low setting with no problem at all for the rest of the year.

I watch my chemistry really closely, try to keep things balanced, etc. Would anyone be willing to have a look back at my logs to see if they can see anything that would help? We have a very simple pool - no rocks, no water features - just a rectangle hole in the ground. I brush during opening though I seldom find anything other than a little black gunk in the skimmers from over winter stale rainwater getting in, which I clean up with chlorine. I pull the cartridges out of the filter and make sure they are stored dry all winter. Is it possible that the RV antifreeze is causing me issues? I use about a half gallon per line. I run the skimmer lines to waste when opening, so I don't put that in the pool, but the returns (3) all empty into the pool water when I pull the plugs and fire everything up. What am I missing here? If this is what I'm in for every year, it's just not worth it. Sorry for the bad attitude - I've had it with this thing. Any suggestions or questions are welcome. I'd love to be as excited to have the pool as I was the first two years.

Thanks!

Wes
 
You pick up algae while your pool is closed or during the opening. The algae sits dormant in your pool. When you heat the water, it wakes up the algae and starts the algae bloom.

You must immediately add FC to at least 1/2 SLAM level upon opening, within an hour of the pump being turned on and water circulating.

Then, consider doing a Pool Care Basics to confirm that there is no algae before heating the pool.
 
View attachment 644451View attachment 644452

You let your FC get too low for your CYA. Wasn't the heater. Follow this...Link-->FC/CYA Levels
Yep - I understand that - and I wish it was that simple - but that was after the pool began eating chlorine so fast that the SWCG couldn't keep up, even at max with the cover closed. Given that, I think this was just the eventuality - not the cause. I can maintain FC with my IC40 at 10% with the cover closed normally. It was at 30% (max with cover closed) and 100% when open, and it couldn't keep up. Once I get through this SLAM, I'll need no more than 35% or so at peak season with the cover open and 10% with it closed. Doesn't add up.
 
You must immediately add FC to at least 1/2 SLAM level upon opening, within an hour of the pump being turned on and water circulating.
Thank you. This is news to me - I totally missed it. I don't raise it that high initially - and certainly not within an hour of starting circulation. How long would I keep it this high? Until it passes OCLT?
 
So two easy things.

1) I want you to always think about *when* you test and how it relates to the daily UV.

On this day, you lost a few ppm from 11A to 6P, but you landed in the clear

Screenshot_20250509_220010_Chrome.jpg


However on this day, you finished the day in te clear and hadn't made back your reserve to start the next day. These 2 measurements are very close, but miles apart if you think about what's going to happen in the next 12 hours.


Screenshot_20250509_220035_Chrome.jpg


2) dont raise your CYA right away because a 40 or 50 is probably plenty in the early season. Keep the FC up like CYA is 70, but if you do somehow need to slam the FC target is much less.

**** edit because you just supplied more info. 🤣 (the above still stands)


How long would I keep it this high? Until it passes OCLT?
If you'd fail an OCLT, then its slam time no matter what. Passing an OCLT after opening should be mandatory IMO. Otherwise any algae wakes up and quickly overwhelms you as it appears has happened each spring.
 
Welp. Here we are again. First week of May, and I'm back in a SLAM because the pool started losing chlorine slowly after heating it. Every. Single. Year. For 3 years. It's fine when opening, I start to heat it, and I end up in a 15-day SLAM, using 40 gallons of chlorine, requiring tons of work, and making me fantasize about filling this stupid hole with sand instead of water. Once the SLAM is through, the SWCG holds chlorine at a low setting with no problem at all for the rest of the year.

I watch my chemistry really closely, try to keep things balanced, etc. Would anyone be willing to have a look back at my logs to see if they can see anything that would help? We have a very simple pool - no rocks, no water features - just a rectangle hole in the ground. I brush during opening though I seldom find anything other than a little black gunk in the skimmers from over winter stale rainwater getting in, which I clean up with chlorine. I pull the cartridges out of the filter and make sure they are stored dry all winter. Is it possible that the RV antifreeze is causing me issues? I use about a half gallon per line. I run the skimmer lines to waste when opening, so I don't put that in the pool, but the returns (3) all empty into the pool water when I pull the plugs and fire everything up. What am I missing here? If this is what I'm in for every year, it's just not worth it. Sorry for the bad attitude - I've had it with this thing. Any suggestions or questions are welcome. I'd love to be as excited to have the pool as I was the first two years.

Thanks!

Wes
Is the reason you are doing a SLAM solely based on using lots of chlorine? Heating the water makes chlorine get used up faster.

I’d look at leaving the cover off more (to get rid of the extra CC’s). Covers seem to also hold algae junk so you might try cleaning it if possible.

The SWG percentage setting isn’t all that useful to worry about. Dont use that as a judge for anything. They get old and wear out, sun changes, etc. I’ve never worried about my percentage setting but I would suggest running the FC hotter when you open the pool in the future.
 
Thank you. This is news to me - I totally missed it. I don't raise it that high initially - and certainly not within an hour of starting circulation. How long would I keep it this high? Until it passes OCLT?
There is little cost in initially raising your FC up using liquid chlorine at opening. Then maintaining it there while the weather is cold and no one is going to be swimming.

Then monitor the daily FC loss and see if it is reasonable or seems excessive which would indicate possible algae and a Overnight Chlorine Loss Test.

That is all part of my pool opening routine for the first two to three weeks. Usually my water is too cold for the SWG and using liquid chlorine lets me see what is happening with FC demand.