How much chlorine on hand for SLAM?

[chazalicious]

After years of getting by relatively okay using pool store tests and dosing, now that I'm trying to limit trips out, I decided to finally try the TFP method, in hopes that I'll be able to stop having to periodically fight off algae. So I got a TF-100 kit last week, and now I have questions!

After opening, I had a lot of Crud in the pool and very cloudy water. Several filter cleanings and vacuumings later, the water's very clear. Initial pool store tests weren't actually that bad, and were pretty close to the numbers from the TF-100. FC has consistently been low though. After the initial pool store visit, I added 2 lbs of powder shock. Then got the TF-100, and FC was still reading in the .5 range, so over the last two days, I've been following Pool Math's recommendations, and added 1.75 gallons of 7.55 Clorox. One gallon of that went in last night, and this morning, FC was down to .5 again. I'm also noticing that while the water is clear, I'm definitely starting to grow some algae. I've read enough on here to know that I should probably start a SLAM.

I've never done one of these before. Since I'm trying to minimize trips to the store, how much chlorine should I stock up on? The pool store has 5 gallons of 12.5% liquid chlorine for $20, which seems like a good deal to me. I just don't know how fast I should anticipate burning through it. Pool Math says it'll take me just under 2 gallons to get it up to SLAM levels for my 40 CYA. Given that the water looks good, am I likely to be able to get through the process with just 5 gallons, or should I plan on getting 10 right off the bat?

Secondary question! I've got a set of Confer stairs. I power washed them off before putting them in this season, but I've never been able to get them to drain completely, and I have a suspicion that they might be harboring algae. I'm planning to pull them, disassemble and fully drain them as best I can. Is there a better way to get the inside of those cleaned out or plugged? The holes are really small, so I'm sure it's letting water in, but not circulating well, so I'm guessing it's harboring something. We're also thinking about just replacing them with a ladder or something we can weigh down that'd be easier to clean under if that's a potential problem.

 

[tillmac62]

A gallon of 12.5% adds 8.9ppm FC to your pool. Typical loss (after you've killed all the algae via SLAMing) is 2 - 4ppm per day. Consequently, you can expect to consume a gallon of 12.5% chlorine every 2 - 4 days. How much you need for the SLAM depends on how bad the algae infection is and how closely you follow the SLAM process. Buying 10 gallons now is reasonable.

 

[Mdragger88]

I’d go for the 10 gal. (Rather have & not need than need & not have) it will get used.
Then pull those steps out & clean the tar out of them with diluted bleach & see if you are able to drill more holes in them to facilitate flow & periodic scrubbing.
A pic of them may help us help u determine what to do with them.

Definitely check & scrub all the other hiding places for algae too like lights, skimmer throat, weir foam, jets etc.

 

[chazalicious]

Thanks for the context on how much chlorine consumption to expect under "normal" circumstances. Up until last year, we had an in-line chlorine feeder that used pucks, so I haven't been sure if I should be expecting to add a cup or two of chlorine per week, or gallons. The pool only gets direct sunlight for the first half of the day, and is in full shade from ~1:00pm onward. Is that going to affect FC loss, or are direct and indirect sunlight about the same for burning it off?

It's been more tricky because last year, my wife wanted to try and use less chlorine, so the pool store said they'd had people switch over to using a UV sanitizer, and that let them go down to almost no chlorine. So I swapped the chlorine feeder out and put the UV thing in, and I don't know if that's good or bad. It's there for now, at least!

 

[tillmac62]

UV systems:

UV Systems - Further Reading

www.troublefreepool.com

Plus you already have the greatest UV sanitizer system known to man, the sun.

 

[chazalicious]

UV systems:

UV Systems - Further Reading

www.troublefreepool.com

Plus you already have the greatest UV sanitizer system known to man, the sun.

If only I'd seen this last year. Oh well, damage done.

 

[Mdragger88]

Also no more clorox - they now have additives(cloromax) in all their products- so cheepo plain unflavored non splashless is the way to go if u need to get some @ the store or if course the lc in the pool area .
& pucks aren’t evil you just need to be aware of everything they do - like increasing cya & lowering ph over time. We generally don’t tell people to rip out their chlorinators lol but to just reserve their use for vacation/travel etc.
Welcome to the forum btw & if you have questions during your slam fire away!

 

[chazalicious]

So I think I might be done with my SLAM? I added some acid last Thursday to get the pH down to ~7.3. Friday morning, vacuumed, brushed, and hosed down the filter, then brought the FC from .5 (!) up to 16 against a TA of 40. I was able to check pretty regularly Friday, Saturday, and Sunday. The lowest the FC got was 8.5 yesterday, but that was after about 7 hours, four of us swimming, a really hot and sunny day, and a downpour that probably added an inch of water. The water was already clear when I started, and I'm pretty sure it was looking even clearer on Saturday. There was algae growing before the start, but it was limited to a few green patches on the walls and a really light haze on the bottom.

The entire time, my CC was between 0 and maaaybe .5. I decided to try the OCLT last night, so I did a test and added some more chlorine around 1am, then got up at 6am and tested again. FC was at 15.5. So I think that means I'm done? I wasn't really expecting to be done so quickly. All the writing here suggested it might take a while, and I thought I might be harboring some algae inside my steps, so I was expecting to fail the OCLT and need to take the steps out and blast them with chlorine inside.

But with the OCLT result coming back at .5, does that mean I'm good? I only allowed 5 hours between the post-sunset addition and the morning check, so maybe that wasn't long enough? Or was it a really short SLAM because the water was already in good shape and just needed a kick in the butt?

One other question I had is about the TF-100 and the daily testing. I know I'm supposed to use the OTO test daily, but I thought that was also not the most accurate, and the FAS/DPD test is better. So now that I seem(?) to be good, is the routine from here to use the OTO daily, add chlorine based on those results, then do all the accurate tests once a week to make sure everything's staying in line?

 

[Mdragger88]

Please read the instructions for Overnight Chlorine Loss Test
You must test after your nightly addition as well not just before so u are sure of your exact fc level.

 

[chazalicious]

I've re-run the OCLT the last two nights, re-checking the FC levels an hour or more after the last chlorination of the night. The first test came back at 2ppm lost. Yesterday afternoon, I pulled the stairs out, and vacuumed the whole pool again. The stairs and mat had a tiny bit of green in some crannies, and there was one small patch on the wall.

With the stairs out, I tilted them back to drain as much water as I could from them. I also popped a few 3/8" holes in a few spots to see what came out, to try and get a better look inside, and potentially to help with circulation. Some of the sand drained out along with water, and there were definitely some green chunks that came out with the sand. The steps came with the pool and had sand already in them, so I've got no idea how old it is.

I left the steps out overnight, and the OCLT came back at 1.5 lost. That's .5 higher than a pass, but I'm not confident that my execution of the test is making it accurate enough that .5 isn't within the margin of error.

I think my plan for now is to keep the chlorine elevated today and re-run the test tonight. If I'm still close but no cigar, the only other places algae could be hiding is caught in the filter or somewhere inside the pump or return plumbing. The pressure on the filter hasn't risen enough to say it needs to be cleaned, but is algae in there potentially still consuming chlorine?

I also need to figure out what to do about the steps. I think my options are either to replace them with something that doesn't let water inside the steps mingle with the pool, drill a bunch more holes to improve circulation, or get some silicone caulk, plug the holes that are there, and drop them back in with some weights. I'll probably start with option 3 since it's the cheapest.

 

[Mdragger88]

Keep slamming @ fc target of 16 until u pass all 3 end of SLAM Process criteria.
You’re getting close! Brush brush brush!
If you’re @ 20% to 25% over clean pressure or if you’re getting reduced flow you could definitely backwash.
Definitely address the steps - bleach & scrub!
- the removable weights are a good idea- many people here have done that w/ capped pvc & concrete. Just do a search for ideas.
Slam on!