To SLAM or not to SLAM

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PoolBeginner

New member
Jun 30, 2020
3
Encino, CA
Pool Size
29000
Surface
Plaster
Chlorine
Liquid Chlorine
Hello,
Been lurking here since a few weeks ago and I'm ready to tackle my pool.
Short background:
Different pool services have been maintaining my pool in the past. But water was not always crystal clear but acceptable and they kept maintaining it just the way it was. Occasionally they "shocked" and used tablets and powder to maintain. Every few months my filter gets higher PSI and my gas heater wouldn't run due to lack of flow pressure. Pool service tells me to change filter because too small, and backwash is broken. Everytime (seems like every month or so) they want to clean filter, charge is $175.
So I joined TFP and have learned a lot. Ordered the test kit and am ready to tackle this.

I feel like I have algea and that's why my filter keeps running slow after a couple of weeks. Water is always clear but at the bottom when I brush or walk on it, a light green cloud appears.
While I was waiting for the test kit, I added 1 gal of 10% chlorine each day for 2 days, just to clear thing up. I also cleaned my filter (thanks to TFP and youtube) twice within a week.

Here's the stats:
Pool: 29,000 gal, plaster, built probably in late 1950's
Location: Southern Calif

Filter: Pentair DE 2000 48sf.
Deep cleaned it last week, had a lot of dirt. Took me 3 hrs to clean the tank and the cartridges with high pressure nozzle. Added DE to filter, and 1 gal of bleach to the pool. PSI started 18, then in 2 days went back up to 30. Cleaned for second time, this time only took me only an hour, and it was lot cleaner. PSI started 17 and it's been a week reaching to 19. Added another gal of 10% chlorine.

Then my test kit arrived:
I tested at nightime,
pH 7.2
FC 10
CC 0-0.5
CH 275
TA 60
CYA 90-100 :( I expected it since it has been maintained with tablets)

After 8 hours, before sunlight hits the pool
FC 9-9.5
CC 0-0.5

So my question:
1. Should I start SLAM at this high level of CYA? Even though the OCLT passed and water is clear, I still see whitish/grayish/greenish cloud when I brush the walls and floor (not as bad as before I cleaned the filter). I'm in So Cal and water is not cheap to partial drain and replace. If I have to, I will. Keeping high CYA means need FC 10 to maintain and that might be expensive in long run.
2. Do I really have algea? Or could it be my plaster, from slightly low in TA, CH, and pH, and being a 60 yr old pool.
3. If I do SLAM at this CYA level, should I keep the PH at 7.2, SLAM, then inc to 7.4?

Thaks a bunch.
 
Welcome to the forum! Great start on ordering a proper test kit and taking control! Can you now fill out your signature -- it really helps us help you.
It will make your life much easier to lower your CYA by draining about half of your water and refilling with fresh. I assume this is a plaster pool, so you need to take into consideration the risk in draining an older plaster pool.
You should follow the SLAM Process. But, if you are concerned about draining, and have been happy with your water quality so far, you could keep your FC at 10+ ppm (testing pH when you test a FC of 10 or under) and ride it out until fall/winter. There would be much less risk in doing a partial drain in November. You will be cleaning the filter often, though as you see, it should not be as bad as before.
Follow the FC/CYA Levels
Your pH and TA will rise as you have stopped using all forms of solid chlorine (correct?).
I suggest you read ABC's of Pool Water Chemistry.
 
I still see whitish/grayish/greenish cloud when I brush the walls and
Click to expand...
Technically, that fails the clear water test "any visible sign of algae".

I am gonna' suggest a "modified" SLAM.

1. Disregard your pH until this is over

2. Disregard your CC's until this is over

3. Bring your FC up to around 25 or so and hold it there by testing and adding about twice daily

4. Brush the pool walls and floor at least once daily

5. Run the robot/vac

6. In 48 hours, the dust should be gone. If it is, perform the OCLT and pass that and then you are done.

Let your FC drift down to around 8 or so and keep it there because of that too high CYA. You need a partial drain and refill to get your CYA down to around a mangeable 50 or so.
 
Thank you for your responses.
Here’s an update on my progress. Still need help.
I cleaned my filter, started SLAM and kept FC level to 25-30 for 4 days meanwhile brushing the walls and floor once daily. Then I passed all the criteria. Clear water, no sign of visible algae when brushing, and OCLT of <1.
Water looked fantastic and I allowed the FC to drift down which took about 10 days. It is now at 7.5.
BUT, this morning, I noticed again, the whitish dust (lot less than before) when I brush the floor.
Here are the numbers:

Before SLAM:
pH 7.2
FC 9.5-10
CC 0.5
CH 275
TA 60
CYA 90-100

SLAM FC 25-30

After SLAM
pH 7.6-7.7
FC 7.5
CC 0.0
CH 200
TA 50
CYA 80-90 (we had couple of hot days that I had to fill up my pool due to evaporations, but I’m not sure if just adding water will lower CYA).

1. Should I SLAM again? Did I let FC drift too low. Water still looks great but I’m just getting paranoid of getting algae. TFP has become my new hobby.

2. Could it be my plaster. I notice my TA and CH at minimum or less.

3. Could it be my filter leaking DE. I hardly doubt it because the white precipitate happened after 10 days. The PSI is steady and working fine.

On a side note I started getting metal stains (they are not slimy, wont brush off, and look like rust in shape of long slender ovals) on the floor which I DID have before but got some new ones . My main drain is original copper piping. But last year I changed the return and pump piping to PVC. Also last year changed my dinosaur gas heater to new Pentair. I will start to see how I can remove the stains with Vit C. Or maybe use sequestrant.
 
CYA of 100 is just wayyy too high for a manual chlorinated pool, it's even a touch too high for a pool with a salt water generator. You need to chop that in half, which usually means draining half the pool, and replacing half the water with tap water effectively reducing the CYA by 50%.

It's my understanding at such super high levels of CYA, the chlorine cannot do it's job to santize and sterlize the pool.... so slamming or even regular chlorination won't help prevent or clear algea blooms or any other bilogical growth in the pool.
 
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