My SLAM experience (so far)

[TomTucker]

Hey all
I've been lurking for a couple months now as we've inherited a pool with our new house.

25k gallon pebble tech plaster (2014)
Tagelus TA60D sand filter (2008)
Pentair Challenger main pump - 1HP Centurion motor
Booster pump (unsure of brand) - 3/4 HP Centurion motor
Pentair LL505G Kreepy Krauly Legend Pressure-Side (2014, I believe)
Taylor K-2006
Midwest, St. Louis

I'm a controls engineer that worked in process for years so I've been around my fair share of pumps, tanks, chemicals, etc.
But I know pool stuff is a whole different animal.

The pool was apparently not opened last year as the woman was having some family stuff going on.
We have a mesh Rayner cover, it fits well and kept more out than it sounds like other mesh covers do.

As the pool wasn't opened last year and I had no idea what I was getting into; I expected the worst.
So I decided to get an early start on it and took the cover off about a month ago.

The water didn't look all that bad, I was a bit relieved.

The following is more or less my log of events/additions/tasks performed. My questions are at the bottom.

My first test results were pretty much what you'd expect for a 'clean' plaster pool that sat for a summer:
3/23 - 5:00pm
pH >8, estimated at 8.2
FC 0
CC 0
TA 40
CH 120
CYA <30 (did not register), estimate 0

So my first task was to fix the water before performing a SLAM
As I pondered my approach and since it was so early and my first time doing this, I tested again the next day.
As you might expect, the results were almost identical.

3/24 - 2:30pm
pH 7.9-8 high
FC 0 low
CC 0 low
TA 40 low
CH 120 low
CYA <0, estimate 0

So I begin to fix the water balance...

3/27 - 10:00pm
*Added 24lbs of baking soda
Pool Math shows TA 40->90 as 18lbs of baking soda.
I'm not sure what I was thinking with 24lbs.
This was before I started writing my PoolMath calculations down before making additions.

3/29 - 7:00pm
TA 120 (of course it was high)
pH ~8.2-8.4 estimate. Scale only goes to 8

3/30------------------------------------------------------
12:00pm
*Added 64oz muriatic acid
2:30pm
pH ~7.45 ok
TA 100-110 better, still a bit high
CH 120-130 low
8:00pm
*18lbs calcium chloride added
I did get water tested at Leslie's (I know, I know) and they said my CH was 200ppm.
So, I decided to split the difference and basically add ~100ppm (~18lbs) to the pool.
That way, if my taylor kit was correct we'd go from 120->220ppm and if Leslie's was correct we'd go from 200->300ppm..either way I'd stay in the 200-400 recommended range.

3/31------------------------------------------------------
5:00 pm
pH ~7.45 ok
TA 100-110 ok
CH 210 ok

During the above, I was constantly thinking that I was having circulation issues.
I also knew I may have to get into my sand filter at some point, as it also could be contributing.
I added unions to allow the multi-port to be removed when needed.
Coming from a maintenance background, shame on the last person to pipe this filter for not installing unions. It's literally the same difficulty as a coupling...alas.

I also got a hose bladder and blew all the lines back and forth. Circulation seems okay but suction still seems impeded (i.e. I can never seem to get my returns to 'swirl' or 'vortex' like I've seen on Youtube).
Old pressure gauge has read 20psi the whole time. Old pressure gauge is old.
Don't trust it, but still note that pressure seems high.

4/1------------------------------------------------------
8:00 pm
Filter run with discharge union open. Pressure is the same 20psi, as always, have never seen it change. So the problem is not the return piping.
9:45pm
*I'm getting worried as the temperature is going up, so I went ahead and dumped 2 gal of 10% chlorine in just to have something in there (and see how fast it gets consumed). PoolMath showed FC 0->10 is 256 oz.

4/2------------------------------------------------------
6:45 am
FC 0.4 (25mL test)
CC 0.4
pH ~7.45
Yep, as you might suspect, its all gone.
Now wondering about ammonia since all my CYA was gone.
6pm
(prep for SLAM start)
want to lower pH ever so slightly, ~0.2 down
*added 64oz muratic acid.
6:45 pm
pH 7.25
good number to start SLAM
7:30pm
ammonia test (add bleach to 10ppm, wait 10 min, if FC < 7 or CC > 2, ammonia may be present)
*256oz (2gal) of 12.5% added (0->10ppm @ 0 CYA)
7:45pm
FC 6.6 (25mL test)
CC 1.6
8:00 pm
FC 5
CC 2.25
well it sure is getting eaten up quick!
8:10pm
New pressure gauge installed...clean filter pressure = 15psi.
PoolMath FC 5->10 @ 0 CYA = 128oz of 12.5%
*added 128oz of 12.5%
*hung 4 lbs CYA in socks (PoolMath says I need 6lbs to get to 30CYA, you can only fit so much in a sock)
9:20pm
FC 5.5
CC 2-2.5
PoolMath 5.5->10 @ 0 CYA =115oz of 12.5%
9:25pm
*added 115oz of 12.5%
10:30pm
FC 9.5
CC 1.5
PoolMath 9.5->10 @ 0 CYA = 13oz of 12.5%
*added 13oz of 12.5%

4/3------------------------------------------------------
7:00am
FC 6.5
CC 0.5
CYA is about half gone
PoolMath 6.5->10 @ 15 CYA= 112oz of 10%
*added 112oz of 10%
12:10pm
FC 7.5
CC 0.5
PoolMath 7.5->10 @ 15 CYA = 64oz of 12.5%
*added 64oz of 12.5%
7:30pm
FC 10
CC 0.5
paranoid, I tested FC/CC twice to make sure it was accurate
CYA aprox 70% dissolved
*added the last 2 lbs of CYA to the socks
one (1) PSI rise on the filter has been noted, whoo!
Rain is expected and I have a higher CYA now, so FC target is now 12.
PoolMath 10->12 @ 25 CYA = 51oz of 12.5%
*added 51oz of 12.5%
9:30pm
FC 11.5
CC 0.5 - 1 (aprox 0.75)
Brushed whole pool

4/4------------------------------------------------------
6:45 am
FC 9
CC <0.5
Pool Math 9->12 @ 25 CYA = 77oz of 12.5%
*added 77oz of 12.5%
12:15 pm
FC 14.5
CC 0.5
pH 7.4 (I understand this is known to be unreliable at FC levels >10)
Filter pressure is at 23.5psi, going up!
6:00 pm
FC 14
CC <0.5
8:15 pm
backwash, didn't record final psi
8:15-9:15 pm
brushed whole pool
9:50 pm
FC 14.5
CC <0.5
pH 7.4

4/5------------------------------------------------------
6:30 am
FC 12.5
CC <0.5
Filter pressure @20psi
5:30 pm
FC 12
CC <0.5
6:45-7:45 pm
brushed, Filter pressure = 23 @ 7:45
backwash
Brushed whole pool again
10:30 pm
FC 11ppm
CC <0.5

4/6------------------------------------------------------
8:30 am
FC 10.5
CC <0.5
PoolMath 10.5->12 @ 35CYA = 38oz of 12.5%
*added 38oz of 12.5%
Filter pressure 17psi
At this point I'm about going crazy wondering why I can't get the filter to plug up after brushing extensively. Water has been cloudy the entire process and is now getting worse. I'm beginning to question my equipment again. The only thing I have not checked is inside the filter. The chemicals are behaving themselves (my CC has been low for a while now) so I'm thinking it must be a filtration issue.

4/6------------------------------------------------------
8:30 am
FC 10.5
CC <0.5
Filter Pressure = 17psi
PoolMath 10.5->12 @ 35CYA 38oz
*added 38oz of 12.5%
8:30-11:30pm
NEW SAND! Quikrete Pool Filter Sand
Filter pressure 15psi
11:30pm
FC 9
CC <0.5
CYA 33-35ppm
PoolMath 9->12 @ 35 CYA = 77oz of 12.5%
*added 50 oz 12.5%
seems like too much, it spiked last time I added so I went light
brushed shallow half

4/7------------------------------------------------------
7:30a
FIlter pressure 25+ PSI pump lost prime...it worked!!
backwash
10:30a
Brushed deep half
filter pressure still 15psi
Running low on R-0871 for chlorine titration
FC estimated @ ~11ppm
12:00 pm
Filter pressure 23psi
12:30 pm
Filter pressure 25psi
1:00 pm
Filter pressure 26psi
backwash
3:00 pm-7:00 pm
3 rounds of DE add and backwash
7:00pm
FC 9.5
8:00 pm
PoolMath 9.5->12 64oz of 12.5%
*added 64oz of 12.5%

4/8------------------------------------------------------
3:00 am
paranoid, it has been 8 hours since backwash, shut pump off
6:30 am
backwashed so i can leave for the day
2:30 pm
Brushed
FC estimated at 9.5
4:00 pm
PoolMath 9.5->12 = 64oz
*added 64oz of 12.5%
6-6:30 pm
Brushed again, PSI=16.5
7:00 pm
PSI = 25
backwash
8:30 pm
FC 12.5
CC ~0.75
CYA measured at 35
Shock target for CYA @ 30 - 40 = 12 - 16ppm FC :: CYA @ 35 = 14ppm FC
PoolMath 12.5 -> 14 = 40oz of 12.5%
8:30-9:15 pm
Brushed
9:15 pm
PSI = 23, backwash

4/9 ------------------------------------------------------
6:45 am
Backwash
12:30 pm
FC estimate at 12-13...32oz to raise approx 1ppm
still running low on chlorine drops, hence the estimate
*added 32 oz of 12.5%
6:15 pm
FC 13.5
CC <0.5
6:30 pm
Vacuumed 25 min, PSI=15
7:00 pm
PSI=16.5
Drop Refill arrived.
Moving the shock target to 15 ppm for a day or two because the last few days have been estimated chlorine levels.
FC 13.5 @ 6:15 -> 15 @ 35 CYA = 48oz of 10%
*added 48oz of 10%
7:10-7:40 pm
Brushed floor and some walls
7:45 pm
FC 14.5
CC <0.5
8:00-9:00 pm
brushed more
two rounds of DE add & backwash
10:00 pm
FC 12.5
CC <0.5
PoolMath 12.5 -> 15 = 64oz of 12.5%
*added 64oz of 12.5%
10:20 pm
brushed whole pool
Filter pressure = 18.5
backwash for evening
I seem to be in aprox x3 per day backwashing cycle but not seeing visible improvement.
If anything its steady at 'Poor'.

4/10------------------------------------------------------
6:30 am
PSI = 23.5
backwash
FC 13.5
CC <0.5
PoolMath 13.5->15 @ 35 CYA = 38oz of 12.5%
6:45 am
*added 38oz of 12.5%
12:00 pm
FC 13.5
CC <0.5
PoolMath same as last add
*added 38oz of 12.5%
7:20 pm
FC 14.5
CC <0.5
7:30 pm
I've tried to scoop off the bottom with a net many times and never got anything.
Brushing didn't feel like there was anything down there, either. Naively, I thought it was clean.

Out of desperation (and partial insanity...I forgot about the polaris), I went and bought a cheap vacuum at walmart.
I got some pine needles and small sticks in the pump basket using the vacuum.
Now I know there is junk down there...and I remember about the pool cleaner.

I figured...toss 'er in.
Holy cow, that thing pulled up tons of gunk and sand and silt from the bottom. Probably about the same volume as a small loaf of bread, for comparison.

10:20 pm
FC 14.5
CC <0.5

4/11------------------------------------------------------
7:40 am
FC 13.5
CC <0.5
Ran the polaris for about 2 hours, until it was not picking anything up anymore.
Brushed the floor
2:00 pm
PSI = 24
backwash

If you've gotten this far, I sincerely commend you.

I have two main questions

1) Now that I've gotten all the junk off the bottom, I’m hoping the pool should be clearing up shortly. Is there anything I’m missing? Wife is beginning to grow impatient. I've been at super chlorinated levels now for about 10 days, but it feels like forever. Do I risk any damage to my finish? which leads to the next question...

2) my LSI is low...I guess I just didn't think about it when I was setting my target levels. But I think the easiest way to fix it now is to add some calcium. Can I do this now at the end of the slam (like where I am now?) right after a backwash? Or am i better to wait till I'm done? I pulled some pebbles up in the vacuum and am a bit worried now. Who knows, they could have been there, or the vacuum may have knocked them loose...but maybe because they were loose because the CH was low for so long.
Any which way, I need to get the water in balance and, of course, would like to do it sooner than later.

I appreciate any help or comments!

 

[mknauss]

Welcome to the forum!

I read it - wow. OK, can you fill out your signature. Look at mine, more detail the better.
It would have been so much easier for all of us if you had used the PoolMath app. See the link in my signature.
Sand filters take a very long time to clear a pool. Especially one like yours. If you had posted at the start, we probably would have encouraged a water exchange with fresh, unless you have water restrictions or are on well water.
Low LSI (we prefer CSI from PoolMath) takes time to cause damage. Any you had was probably from the past. Focus on SLAM right now.

All for now - keep asking questions!

 

[YippeeSkippy]

I guess my only question is about adding the DE then backwashing. You know that just sends the DE out again, right?
And if you use too much DE, it by itself can really raise your psi, so I wondered if that wasn't what you were seeing that caused you to backwash so much?

Sand is a great, simple filter......but it tends to be the slowest to clear. It'll do it just fine but ya gotta be patient. And remember that a slightly dirty filter actually cleans better than a pristine clean on. Odd, huh? But true!

Your water looks like its in the "gotta have patience" stage.... keep at it and one day (soon we hope!) you'll wake up and see clear blue! Since its still to cold to swim you're not missing anything, you're getting a little exercise with all the brushing and your wife is gonna be so proud of the *sparkly* clear water you'll be having. I promise!

Maddie

 

[ajw22]

We always round up CYA. There is no markings for CYA 35. The markings are logarithmic, not linear. You can’t eyeball values in between the lines.

So your CYA is 40 and your shock FC should be 16 or greater. I see FC values of 13 & 14 in your recent log. A SLAM Process will take a lot longer if you don’t get above the shock FC target. See Chlorine / CYA Chart - Trouble Free Pool

 

[TomTucker]

mknauss
Thank you for the welcome I was able to do multiple adds via the poolmath app and it seemed to work okay. However, I couldn't figure out how to add another set of new test results after my initial set so I gave up and used good ole pen and paper. But I use it every time I make an addition; I just manually input whatever the current conditions and goal are. I will update my signature!

YippeeSkippy
I am aware that the DE is gone after each backwash. I was just trying to do anything I could to help it along! That's why I'd try to do rounds of it, i.e. one after another. I'd put in about a 1/2 cup (what would raise my filter pressure 1psi) and usually after 45min-1hr the filter pressure would be 25psi. Obviously, it make have no difference if there was the gunk at the bottom of the pool that I cleared out wed night/thurs morning. Alas, maybe I'll try again this weekend.

I am aware a dirty filter cleans better than a clean filter, but thank you. I try to let it go for as long as possible before I backwash, as I know I'm getting the finest filtration at that point. However, I also know there is a trade off where you begin to impede your flow and eventually your pump can't overcome this resistance and begins to cavitate and eventually lose prime. I used to work on oil and water delivery systems for metal forming equipment and this was where I learned a fair amount about how filters work. I wish I had lots of $$ so I could toss a PLC and pressure/flow sensor on the filter and automate this process!! Now just to find a actuator that fits a multi-port valve, ha (Just to be clear I won't really be doing any of this, as much as one can dream)

ajw22
Oh man, I feel like I did read about rounding up CYA a while ago but totally forgotten that tidbit.
I appreciate you pointing that out. I've gone up this morning to FC 16. Pool was looking slightly clearer, I didn't have time to grab a picture as I was rushing to get to work!
One question, you say "FC should be 16 or greater". Should I be shooting for greater? Like 17? or is it okay if I make the target 16? I am not seeing a lot of FC loss, making adds less and less...which should be a good sign...

Thanks all, I'll keep you posted.

 

[mknauss]

On the PoolMath app, to be able to save your information you need to subscribe to it and login with your TFP member name and password. Did you do that?

When you fully use the app, you can share your data (it is under Pool Setup on the app) so that we can see all your tests by clicking on your Member name. Try mine.

 

[ajw22]

I appreciate you pointing that out. I've gone up this morning to FC 16. Pool was looking slightly clearer, I didn't have time to grab a picture as I was rushing to get to work!
One question, you say "FC should be 16 or greater". Should I be shooting for greater? Like 17? or is it okay if I make the target 16? I am not seeing a lot of FC loss, making adds less and less...which should be a good sign...

Sounds like you are making good progress and are over the hump.

16 is fine. 1 or 2 ppm higher will not hurt.

 

[Richard320]

I read about the first half carefully but then it started getting redundant so I skipped ahead.

Your experience doesn't sound abnormal. You wasted a lot of bleach trying to oxidize the leaves and twigs and pine needles down on the floor. Now you (and all the anonymous readers who will see this) understand why one of the prerequisites is

* Make sure the pool is free of leaves and other debris (at least as much as possible).

That comes even before adjusting pH.

The cloudiness is the worst thing. But consider your pool to be one giant CYA view tube. As the cloudiness clears, visibility is not a straight line progression. You might have removed 75% of the floaties and still be unable to see the change with the naked eye.

The good news is that this could be the last time you ever have to do this.

I am no expert on fancy finishes, but a few stray pieces of grit wouldn't alarm me. Considering the pool sat unattended a long time and that the pH was really high, I wouldn't be surprised if you find patches of scale on the wall and floors. If so, there's where your Calcium went. As you maintain pH going forward, some of it may dissolve back into suspension, but I can tell you from experience that it happens at a glacial pace.