Heavy Rains = Crazy Algae (pool covered)


New member
Sep 8, 2019
New Orleans, LA

We have a 18' x 48" Intex pool with SWG and Sand Filter. Pool has been covered since November and water pretty clear since then, with just small bits of debris going in through the small venting cover holes here and there. Sadly, the water looked good all along so I hadn't tested it. I should say the water looked good until we had loads of days of consecutive rain recently (Louisiana) and now the pool cover has loads of algae on it and plenty of water. Peeking under the cover I see there is algae at the bottom of the pool now too. I've been running the SWG now for about 24 hours with what seems like no progress but I think the cover needs to come off so I can stir the algae around from he pool bottom. But, I am so worried about trying to take the cover off and getting extra algae from the cover into the pool. I've got so many questions and I feel like I'm already so behind in getting this cleared up.

1. How do I attack the pool cover algae? I was going to take a shop vac and try to get the heavy water off of it but wondering if I should also put bleach in that water first for some time.

2. Do I keep running the SWG? Add bleach to the pool also? Shock? I've never added anything to the pool other than salt, muriatic acid, or CYA (all as needed) after first setup last summer so I'm so nervous to add in other things and mess it all up worse.

3. It's supposed to rain badly again this coming Friday and Saturday. Do you think I can fix this before then? And then how do I prevent it?

Here are my numbers (yikes, the zeros!!):
H 100
TC 0
FC 0
pH 7.2
Alk 40

Thank you!!


Gold Supporter
TFP Guide
Jul 21, 2013
Northern NJ
Pool Size
Salt Water Generator
SWG Type
Pentair Intellichlor IC-60
Get the cover off the pool, dump the algae in the pool, stock up on liquid chlorine, buy stabilizer, and then follow the SLAM Process when it stops raining.

Pour 5 ppm of liquid chlorine into the pool daily until you can begin the SLAM Process.

Add 30 ppm of dry stabilizer using the sock method ASAP.

Your SWG is ineffective when your CYA is 0.

I suggest you read ABCs of Pool Water Chemistry



New member
Sep 8, 2019
New Orleans, LA

I was so nervous to remove the cover and start the SLAM and then got delayed with the start due to work. Finally got the CYA in there on 5/1 and started SLAM on 5/3. Still going. Before starting SLAM, my CYA was between 45 and 50 so I set the target FC to 19. Been SLAMMING with the cover on but still brushing in sections and backwash daily. Did that with the cover on because the cover had so much water, algae, and debris. Finally took the cover off last night since it was mostly dry and stuff on it was dead. A bit more algae got in the pool from cover but my FC is good so should have killed it ok overnight I guess. I'm using 10% liquid pool chlorine. Checking and adding 3 times a day when I have work and every few hours on weekends. CC has been 1 almost each time I check, but was 0.5 last night.

Current numbers this morning:
FC 16.5
CC 1

So, I added 21oz of 10% chlorine per Pool Math calculation.

Pool looks minty cloudy. I have read lots in here that the sand filter can take some time to clear it up. Should I have any expectation of how much time before I get concerned that there's an issue with our sand? Last year, the pump sat for several weeks hooked up to our old pool but turned off since the motor froze up. Once we fixed it, we drained and tossed that pool, set up the current one, and got the pump all going. Seemed fine all last year but we never got to a point where the pool was real dirty.

I know I need to just keep SLAMming and have POP. Thoughts on my progress are appreciated. It's my first SLAM rodeo!!

EDIT: btw, SWG is off and I'm in pump-only mode.

6423 gal, Coleman Vista Series II 18' x 48", Intex Sand Filter Pump & Saltwater System with Electrocatalytic Oxidation 0.75HP (Model ECO20110-1), Taylor K-2006 Test Kit

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I also tried just having the first part and got the same message. Tried to message the admin too and got same message.]

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