Do I need to SLAM?

[mc2005h]

Hello! I'm very excited to join this community. I could really use your advice!

I'm a relatively new pool owner (this summer is my second full season). I live in CT and have an in-ground pool. 20x40, about 24K gallons. Chlorine, not salt. Using FiberClear in my filter. I shock with HTH advanced cal-hypo (2 bags a week) and I have 4 tablets of bioguard silk in the floater plus one in the skimmer.

My pool is crystal clear, however, whenever I shock the pool and run the filter once a week at night, I wake up to find clumps of yellowish "dust" at the bottom of the pool. These clumps are mostly concentrated at the deep end, though smaller piles can be found in other areas of the pool. I've been vacuuming these piles to waste.

On Monday June 17th (after having added 2 bags of shock on Saturday night), I went to the local pool store and told them what was happening. We did a water test and here are the results:
Free Chlorine 0.09
Total Chlorine 0.15
Combined Chlorine 0.06
pH 7.6
Alkalinity 73
Adjusted Alkalinity 76
Hardness 207
Cyanuric Acid 8
Iron 0.10
Copper 0
Phosphate 0

The store recommended I add a Phosphate reducer (just in case, even though the levels were 0) and Pool Enzyme, then take out the filter and clean it, vacuum pool to waste, then add 4 bags of shock. I had been reading this forum before going to the store and knew I shouldn't have bought anything, but I caved, spent the $50 dollars and followed the steps. I added the Phosphate reducer and Enzyme monday evening, cleaned filter/vacuumed and topped up water wednesday afternoon, shocked Wednesday evening, and then on Thursday vacuumed to waste the dust that formed again after shocking and topped up the water again. I went to the pool store today (friday). Here are the results

Free Chlorine 0.28
Total Chlorine 0.34
Combined Chlorine 0.06
pH 7.4
Alkalinity 76
Adjusted Alkalinity 73
Hardness 246
Cyanuric Acid 13
Iron 0.3
Copper 0.2
Phosphate 0

While my chlorine levels are up a bit, they are still low. The store suggested I buy zip chlor and add it tonight, but I declined because I wanted to get this group's advice first.

To reiterate, the water is still crystal clear. The only concern I have is why there seems to be dead algae after every shock treatment and why I can't get my chlorine levels to the normal range despite shocking and using expensive floater tablets. I realize now that my frequent vacuuming to waste and topping up the pool (~500 gallons a day twice this week), might also sending out some of the chemicals I added and contributing to the problem... I should probably be vacuuming the dust to filter and then backwashing.

Should I go the zip chlor route or do you think SLAM is appropriate for my situation? Ready to buy the TF Pro if you think I need to SLAM.

Thank you!!

 

[HermanTX]

Welcome to TFP.
First - stop buying phosphate reducer and any enzyme products.
Your FC levels are low because you have no CYA to protect it from the sun (UV).
Buy 2 products - go to Home Depot if you can - they have Stabilizer (CYA) which is needed now. They also have liquid chlorine. That raises FC quickly. What type of pool do you have? Fiberglass, Vinyl or Plaster?

Since you have a clear pool, but you may also have algae.
For 24k gals, you need to add 6-8 lbs of stabilizer to raise CYA to minimum 30.
1 gal of liquid chlorine (can also purchase at Walmart) will raise FC by 4.2ppm. So purchase 5 gals to start.

Also, do not add pucks to your skimmer basket. remove those. Only use a floater with pucks.

The other critical step is to purchase your own test kit. This will allow you to understand your pool and keep you out of the pool store that is just sending you in circles.
Look at Test Kits Compared.

We don’t know for sure you have algae but you need a test kit to run some tests to confirm.
The first test will be Overnight Chlorine Loss Test which will confirm if you have algae or not.

 

[PoolStored]

What @HermanTX said.

Order the kit now. Yes, get the TF-pro. You will need the reagents, and the smart stir is a game changer for accuracy and repeatability in testing.
Add 3ppm of liquid chlorine a day, NOTHING ELSE, until the test kit arrives.
Because you have visible algae, when the kit arrives, start the SLAM process. Link-->SLAM Process

 

[mc2005h]

Thank you both! My pool is vinyl. TF Pro has been ordered and tomorrow evening I will pick up 8 lbs of stabilizer and 5 gallons of 10% liquid chlorine from Walmart.

For the stabilizer
1) Should I add the full 8 lbs or 6 lbs to start?
2) If I add the stabilizer tomorrow evening, can I add the chlorine right after?

For the chlorine
1) I have 6 bags of the HTH advanced granular shock. Can I use that now or during SLAM or should I just focus on the liquid chlorine for now?
2) I'm confused by the 3ppm and 4.2ppm... if I use the liquid chlorine, should I add a full gallon every night until the test kit arrives?

and lastly, assuming it is OK to use the pool as long as the water is clear?

thanks again!

 

[PoolStored]

1) Should I add the full 8 lbs or 6 lbs to start?
2) If I add the stabilizer tomorrow evening, can I add the chlorine right after?

Only add 3ppm of liquid chlorine, nothing else until the kit arrives. We have no idea your current CYA until we test.

For the chlorine
1) I have 6 bags of the HTH advanced granular shock. Can I use that now or during SLAM or should I just focus on the liquid chlorine for now?
2) I'm confused by the 3ppm and 4.2ppm... if I use the liquid chlorine, should I add a full gallon every night until the test kit arrives?

and lastly, assuming it is OK to use the pool as long as the water is clear?

Download pool math. Link-->PoolMath
Setup your pool and use the "effect of adding" in the menu to figure out how much 3ppm is in your pool. Using the Granular shock is *probably* ok, but I would use liquid chlorine.

If the water is clear, and you add the 3ppm, you are probably ok to swim.

 

[mc2005h]

OK, got my test kit. PH 7.5, chlorine barely present if at all, and CYA tube filled to top and I could still see the black dot, confirming pool store results that my CYA was very low. I just added the 8lbs of stabilizer. I'm going to leave the filter running all night. Should I add just one gallon of liquid shock tonight and start testing the FC level tomorrow morning?

 

[PoolStored]

Consider your CYA is now 40. Your SLAM target is 16.

Start the slam process. Link-->SLAM Process

 

[mc2005h]

Last night my FC was 0.5. I added roughly 3.7 gallons of 10% liquid chlorine per the app instructions. We had a pretty big rain storm overnight.

This morning my FC is 18.5-19 and my CC is 0.5. My CYA is somewhere 70-90, which was surprising. I did all tests twice to confirm.

With the CC test, once it stops spinning and sits for 30 seconds, it starts to turn pink again. Is that OK? While it was spinning, just 1 drop turned it from a very very light pink (photo) to clear. When I started the FC test it was a much deeper pink.

Water is clear and there is a small amount of dead algae at the bottom of the pool, but not much more than there was end of day yesterday.

Does the 0.5 CC mean I'm done and just have to wait for the FC levels to drop to normal?

The water level is a bit high because of the rain. OK to drain some?

Thanks!

 

[PoolStored]

With the CC test, once it stops spinning and sits for 30 seconds, it starts to turn pink again. Is that OK?

Normal. Ignore it.

Go ahead and drain some.

Does the 0.5 CC mean I'm done and just have to wait for the FC levels to drop to normal?

No, SLAM criteria is a) OCLT FC drop <=1, b) CC <=.5 AND c) Clear pool. Visible algae means the pool is not clear.

If you are slamming, it is a process. Re-read this. Print it out and follow it..Link-->SLAM Process

What is clear? Link-->How Clear is TFP Clear?

Try these instructions for the CYA test.

CYA - Cyanuric Acid Test

Cyanuric acid (CYA) is the chemical name for the product commonly called “pool water stabilizer” … Read more…

www.troublefreepool.com

 

[mc2005h]

Does my target slam level change because the CYA is higher now or is the target always the original 16? Should I try draining and refilling to bring it down first?

 

[PoolStored]

I would re-do the test. Outdoors, sun to your back. Pour to the first line. Hold at your waist, GLANCE. If the dot is obscured, you are done. Take the number on the line and add 10.

If not obscured, fill to the next line, hold at your waist, GLANCE. When the dot is obscured, you are done. Take that number and add 10.

Something does not add up. 8 lbs of stabilizer should raise your CYA by 40.

 

[mc2005h]

Thanks for that link. I tested outside instead of indoors and its 40. I assumed because my FC was up not down by 1 this morning, that I was done. But now I understand that my goal for today is to not level my FC level fall below 16. If I check often enough, I should be able to maintain 16 until sunset. Then if tomorrow morning it is >15, and CC is still 0.5 or less, and there is no more dead algae. I'm good. If not, continue!

I think I get it. Thanks so much for your patience!!

 

[PoolStored]

I tested outside instead of indoors and its 40.

So, dot was obscured when fill to 30, and you rounded up?

But now I understand that my goal for today is to not level my FC level fall below 16.

Test. Add enough to get to 16. No need to retest. Wait at least 2 hours, test. Add enough to get to 16. No need to retest. Rinse repeat.

Tonight, make final addition. Wait 30 minutes with pump running and do first OCLT test...after sunset. Before sunrise, run pump for 30 minutes (it should be running 24x7 during slam), test FC.

If the FC drop is <=1 and CC <= .5, and pool is clear, you are done. If not, SLAM ON!

 

[mc2005h]

So, dot was obscured when fill to 30, and you rounded up?

So, dot was obscured when fill to 30, and you rounded up?

My back was to the sun, the tube was in the sunlight, and the dot was heavily obscured between 35-40. I did it a few times just to be sure

 

[PoolStored]

Yep, 40!

 

[mc2005h]

Update
OCLT 3, CC 1, the tiniest bit of dead algae I’ve seen after treatment on bottom of pool

Will SLAM on today and repeat. Should I be concerned about algae hiding somewhere or will the Slam FC level kill it eventually wherever it is?

 

[Texas Splash]

Should I be concerned about algae hiding somewhere

Always! Never take any spot for granted. Brush, inspect, repeat. Algae can hind just about anywhere. Show us a couple pics of your pool from different angles so we can see what it's like. Also, you're signature is still blank , so make sure to update that as well.

Create Your Signature - Further Reading

www.troublefreepool.com

 

[mc2005h]

Pics attached!

 

[Texas Splash]

Good pics. Areas I would keep in mind include:
- Skimmer area and behind the weir door
- Under drain covers
- Behind a light if there is a hollow niche in there
- Underside of pool cover
- Submerged portion of ladders; try to like out and inspect, clean, flush if possible.

 

[mc2005h]

Thanks! Will need to get in the pool and inspect for how to take the light cover off. I’ve never done that before.