Looking for SLAM insights - getting stumped - no cc's, clear water, trouble with OCLT + burning through chlorine

doberdragon

Active member
Aug 27, 2019
25
Katy, TX
Water chem is as follows:

FC: maintaining around 24PPM (lowest it has dropped to during process was 20)
CC: 0
CYA: 50-60 (always hard to tell, been running SLAM with 24 target)
TA: 70
CH: low 300's
Salt: 3200 +/-
pH: not reliable now, but generally in the 7.6/7.8 range (water feature tends to keep it high)

Situation: I installed a new Pentair 011056 VSP (got rid of an old Hayward Northstar energy hog!) and a couple smart switches a few weeks back - new plumbing setup looks like this now:

IMG-7278.JPG
IMG-7279.JPGIMG-7280.JPG

In doing this, I had the system down for a day, then I think I had my SWG running too short when calibrating. My FC went real low (I generally keep my CYA around 70-80, and my FC dropped to like 2-3). As well, we have been seeing some small water bugs in the pool (back swimmers?) maybe half a dozen or so a day - and it led me to believe algae was somewhere in the pool as they feed on it from what I read. I could not ever seen major algae issues - water has been clear this whole time. I did get a little green around the bottom of a water feature, which is a PITA to maintain in the first place... this led me to believe I had algae in the system. We also have some overhead power lines - the Pigeons are over them quite a bit and annoy the Crud out me. Do my best to scare them off anytime I see them, but they do pool on the rocks from time to time (nothing huge, but they are birds...)

My Pool looks like this now - water has been crystal clear the whole time - and CC has always been zero:
IMG-7415.JPG
IMG-7416.JPG

SLAM process:
- Washed my cartridge filters before starting
- I have been running the pump 24/7
- I have been running the Polaris 280 2-4 hours a day
- I have brushed down a few times
- I have 50/50 water/bleached the water feature twice
- I pulled my pool light to look for mess behind it and nothing
- Under the skimmer lids I saw tiny amount of algae, bleached those
- We have got quite a bit of rain here in TX, had to drain off water a few times to stop overflowing, but always topped off my chlorine to hit that 24 ppm target
- no ladders that could be 'hiding' algae

Questions / Concerns:
- I am running 24PPM, if my CYA is really 50 not 60, am I burning off excess chlorine as a result and should I be targeting 20PPM? (i.e. if my target should be 20, and I am targeting 24, will that extra "4" burn off excessively fast? am I hurting anything other than wasting money on extra bleach?)
- I am burning through a ton of liquid chlorine bleach (using new Chlorox from Sam's) - I have dumped in ~1800 ounces thus far + I am still running my SWG around 8 hours a day at 80% to keep Chlorine being produced
- I am testing 4-5+ times a day, and dropping 2-4 PPM between tests pretty regularly so losing in the range of 15-20+ PPM of chlorine a day at this point.
- I am failing the OCLT pretty consistently here, losing 2-4 PPM overnight
- After a week of running this process, I seem to have same water clarity, no CC's, but just burning through tons of chlorine a day

Any insights veterans, I have been reading historical thread after historical thread, and just looking for any other tips or suggestions on what may be going on here... something I am missing that can explain how the pool has 'looked' so good, but I have dumped in so much chlorine, still burning through, still seeing a few water bugs, and failing OCLT so consistently.

Thanks in Advance!
 
Last edited:

YippeeSkippy

Mod Squad
Gold Supporter
LifeTime Supporter
Jan 17, 2012
17,629
Evans, Georgia
You can expect to lose 2-4ppm of FC daily to the "Sun Tax" so always aim a little high with your goal FC so you can cover that loss and still have enough in the pool to protect the water.

I've never heard of water bugs being a sign of algae. I assume its a sign of thirst. Some folks claim a touch of Dawn dish detergent in the pool helps due to the way it changes the pressure of the surface. I do not know how much, so you'd be best to research this if you try it.

Stop buying Clorox bleach.....it contains polymers which are NOT good. Clorox has ruined a lot of products with either hidden copper or polymers. Try the liquid chlorine from Walmart (pool section) Lowes or HD.

Any other products put in the pool??
 

doberdragon

Active member
Aug 27, 2019
25
Katy, TX
Thanks for the replay YippeeSkippy

I realize my post was a bit long, but to clarify I am losing way more than the 2-4 sun tax a day, by my calculations with the bleach I am putting in + the SWG runtime, I am losing like 15-20+ PPM a day through this process, every day for a week...

On the water bugs, I figured if they feed on algae, and they are in the pool, has to mean they have a good source there like algae.

Only other product I put a minimal amount in was some phosphate remover... I know that is generally not seen as a recommended product on TFP, but in case all the sunscreen from the family had added a bunch of phosphates, didn't figure it would hurt to remove that extra potential algae food.

I had not heard about Chlorox bleach being an issue on the boards before - I thought it was good to go along with other generic brands, as long as it was not scented or 'splashless'?
 

TriangleMan

Well-known member
May 30, 2021
78
Lake Barrington, IL
Pool Size
25000
Surface
Vinyl
Chlorine
Liquid Chlorine
I'll preface this with: I'm not one of the experts here, just a fellow traveler that went through a SLAM recently with some of the same concerns. It took me weeks to clear the SLAM, and I was very discouraged by the high amount of chlorine I was losing every day, combined with failing OCLTs, in spite of crystal clear water and CC=0.
You can see my own rags to riches story at this link.

Here's some of what I learned:
The CC=0 reading can be misleading. It's a good thing, to be sure, but some things that the chlorine breaks down don't register as combined chlorine (chloramines), and even the things that do will get burned off pretty quickly by they sun.

If the water bugs you're seeing are backswimmers, they eat bugs, not algae. If they are water boatmen, they do indeed eat algae and may be a good secondary signal that you have a problem. I was catching water boatmen in my skimmer and pump basket even when the water was clear, prior to completing my SLAM. It's a good sign that you're not done yet.

You will lose A LOT of chlorine during the day to the sun during the SLAM. I ended up considering this the cost of doing business. The SLAM level is necessary to kill the algae and make it inhospitable to growth, and probably above levels that the CYA can efficiently protect. Consequently, you'll lose a lot of it. My empirical data, for my fully-sun-exposed pool, seemed to show a loss of about 5% per hour. (Chem_Geek lays out a number of invaluable charts at this link that lay out the half-life of FC at different CYA levels and the chlorine usage from UV. It's not quite as simple as 5%/hr but it's clear that the more FC, and therefore the more HOCL, as well as the more CYA, the higher the loss will be). 5%/hr translates to about 50% of your chlorine over 14 hours. So if you're starting at FC = 24 ppm, and putting in more than 10 to 12 ppm during the day, I'd assume until proven otherwise that you're sacrificing half of your FC to the cause and the the remainder is being lost to organics like algae.

The real test is the OCLT. If you're losing 2-4 ppm overnight, then you are still battling something. If you figure about twice as much daylight hours, I'd figure you'd lose about 4-8ppm to that same problem if you're just managing to hold steady, and not gaining or losing ground in the battle (although you should be improving thanks to the SLAM). Again, the difference during the day is attributable to sunlight, so just maintain the SLAM during the day and pay closer attention to any loss overnight.

One of my more controversial takeaways from my own experience, I suppose, comes at the very end, when you're pretty sure you've completed the SLAM but still can't pass the OCLT for some reason. My lesson learned is: Test Very Carefully! Especially at high FC levels, +/- 1 mL in a 10 mL sample means +/- 10%. That's an error that easily exceeds the 1 ppm threshold for passing an OCLT. Be especially careful on your measurements, using clean equipment, and titrating very carefully for repeatable and predictable results. Test 2 or 3 times to be sure you're getting the same answer, if you're not sure.
Consider using children's medicine cups, or syringes, or a sample sizer to assist with precision. When all else seemed to fail me, I dropped down to maintenance level for a night to see if I could pass the test at lower FC levels with more margin for error. I don't recommend this approach, since you'll lose ground against the algae if you're wrong... but it's an option I chose and happened to come out on the happy side and further convince myself that my testing was inaccurate.

From the sounds of it, though, you're not quite at the finish line yet. You've seen visible signs of algae, and clear FC loss overnight that's larger than any likely margin of error.

For what it's worth coming from a layman, I'd recommend continuing the SLAM and trying to figure out where the algae is hiding. (Have you taken apart the weir doors to clean the foam?) It's currently getting the better of you, but its days are numbered! Keep it up, and good luck! Lingering in a SLAM and watching the sun god eat up your chlorine in the process is no fun. No fun at all. But once you come out the other side, it's a sweet sweet victory.

By the way, your backyard oasis is beautiful!
 

mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
44,426
Laughlin, NV
Pool Size
6000
Surface
Fiberglass
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
If the water is crystal clear and you have no debris on the floor of the pool, let the FC drop to below 20 ppm and do the OCLT. As TriangleMan said, testing error may be your issue.
 

proavia

LifeTime Supporter
TFP Guide
Feb 6, 2015
2,534
Chandler AZ
Pool Size
12300
Surface
Plaster
Chlorine
Liquid Chlorine
Have you scrubbed really really well under the rocks, especially at or under the water level?
Have you removed the wier door on the skimmer and checked it thoroughly for signs of algae?
 

doberdragon

Active member
Aug 27, 2019
25
Katy, TX
Thank you all for the replies - really helps give confidence in 'trust the #'s' and keep exhaustively looking at EVERY source there could be.

@TriangleMan - first off anybody who has a TMBG quote in their signature is a good dude in my book, that song brings me back! Super thorough post there, and reading the thread you referenced on your own experience, I feel you! RE: the bugs, I think we actually may have a couple backswimmers and a couple water boatmen. With the landscaping we have behind that water feature + all the rain, I think they run off from there from time to time - and it is hard to completely stop them. I also have another theory - may be controversial here - I just switched to a VSP, and running that thing ~2000 RPM or lower - there is clearly not the skimming suction I had with the old pump running @ 3450RPM. Thus bugs and whatnot do not get 'sucked' in as hard and drown in the bottom of the baskets... I can deal with that for the benefit to the enviornment and wallet on lower energy consumption, but will monitor it. All your other math checks out, and on the testing accuracy, that is a stellar point. I do you as 10ml syringe in my samples, but when testing that water and it is black outside, even the tick marks can be a bit hard to read, so yeah +/- 1ml is definitely feasible. That can throw off an entire OCLT, so I'll be extra careful. As well, my dropped bottle was pretty low, I got a new one in the mail, and I think I am getting more uniform 'drops' in my samples, which helps accuracy as well. Really happy to see you got to a positive outcome, and I feel I am not far off now.

@mknauss - will do - it is a good suggestion and thanks for the backup.

@proavia - good call on the weirs! I hit those rocks hard, and I had scrubbed out my skimmer pots and walls, but I had NOT taken off the weirs, and sure enough, look what I found in the old foam there!
IMG-7419.JPG
It is not a ton, but that is still some algae, and it will throw things off.

Fingers crossed I am close to the finish line, will report back over the next couple of days guys - but yes, what a good point - when you think you have checked everything - your probably have not, keep searching!!!
 

TriangleMan

Well-known member
May 30, 2021
78
Lake Barrington, IL
Pool Size
25000
Surface
Vinyl
Chlorine
Liquid Chlorine
@TriangleMan - first off anybody who has a TMBG quote in their signature is a good dude in my book, that song brings me back!

I love it when I see someone remember the reference! There's at least one other person out there that's messed up for the same reasons that I am! Good times indeed!
I knew the song long before Tiny Tunes picked it up, but I still appreciate their cultured hijinks as well.

Btw, there's another TMBG hit for the new generation. Believe it or not, this theme song is theirs! (and I and my kids love it)

Fingers crossed I am close to the finish line, will report back over the next couple of days guys - but yes, what a good point - when you think you have checked everything - your probably have not, keep searching!!!

So for the important question: How's the algae battle going?!
 
  • Like
Reactions: doberdragon

doberdragon

Active member
Aug 27, 2019
25
Katy, TX
@TriangleMan - yeah, Flood was my favorite album of their's. I remember that Tiny Tunes video - it is imprinted in my mind! If I recall, that is pretty much the 'official' music video for that song + I believe they did Istanbul as well. Good stuff. And funny with the kiddos I have heard that Hotdog song a million times, but didn't put together that was TMBG, awesome to know!

And I am happy to report, finally passed 2 nights of OCLT, so I have been restoring my CYA back up to the 70/80 range, and hoping now my SWG will keep up with the chlorine level desired, and we can be back to enjoying the pool as normal!
 
  • Love
Reactions: TriangleMan

Katodude

Silver Supporter
Aug 22, 2017
1,718
West Palm Beach/Florida
Pool Size
15000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Hayward Aqua Rite (T-15)
Ok, so this part is really important. Run you FC hot for the next few weeks. The big rookie mistake after a SLAM is to let your FC drop to the minimum again, and get another algae bloom.
 

Enjoying this content?

Support TFP with a donation.

Give Support
Thread Status
Hello , This is an inactive thread. Any new postings here are unlikely to be seen or responded to by other members. You will get much more visibility by Starting A New Thread