Algae keeps coming back

[jandersen13]

Hey everyone,
This is my fifth year of owning our pool and this year I have had my worst luck with algae. I’m in Michigan and it did not really get warm until a few weeks ago. Since then it’s been very warm for here (mid 80s to low 90s).

About 2 weeks ago we just got home from being away for 4 days. I first noticed algae on the floor and it was slippery. I use a chlorinator with pucks and it was jammed. I shocked the pool 2 nights in a row and it seemed to turn blue again but was cloudy. Kept running the pump and all seemed to clear up a week later. Then I noticed some algae again and I shocked the pool at night. Cleared up turned blue and all was good. Then this past weekend we were gone for 3 days. Came home tonight and the floor was again covered in algae. Just shocked the pool tonight.

I know this forum does not recommend chlorinators. I know where to go on here to follow the SLAM process. But my question here is what is causing the algae to come back? I’ve never had this issue before. Is it that I need to replace the sand in my filter? I have not done that in the 5 years I’ve owned it.

My numbers have been good since I noticed the chlorinator was jammed. Alkalinity might be a bit low and PH is around 7.2. Do I need to bring those up?

Here are my numbers:
FC - 4.5
CC - 0
TA - 90
PH - 7.2 (maybe slightly below that)

Any help is much appreciated.

 

[mknauss]

As you said, you know how to follow the SLAM Process. Once you have algae in the water, that is what it takes to eradicate it.

 

[jandersen13]

Any thoughts on the sand replacement as well?

Also - I believe it’s green algae but could it be mustard? It’s mostly on the bottom and does have a slightly brown / yellow tint when I brush it. But once brushed the water looks greenish, not yellowish.

 

[mknauss]

Sand does not wear out. You can deep clean, not a bad idea once a year.

Mustard algae is fairly rare.

 

[Donldson]

I may be missing it, but what is your CYA level?

 

[Casey]

You did not say what your CYA is.

You keep saying the pool turned blue. You did not say that it was crystal clear. I'm thinking it was not and once you got to "blue" you stopped SLAM'ING the pool, not completing the SLAM and algae kept coming back. You have to get to SHOCK LEVELS And MAINTAIN it.

 

[skimmerswimmer]

Do you have one of the recommended test kits? The fact that you posted numbers without posting CYA leads me to believe that you aren’t yet fully following TFPC methods. Read pool school a few times, get the TF100 kit, post your results, stop using pucks for now and the fine folks on this forum will help get your pool sparkling in no time!

 

[jandersen13]

Rookie mistake here everyone. I have the TF100 kit and have for a few years based on recommendations here. I completely forgot I hadn’t checked my CYA. I have less than 20 CYA right now. Maybe even 0-5.

I need to add Stabilizer to get things working properly right? Can I do this tonight and also add liquids chlorine to shock to keep things clear tonight?

 

[IceShadow]

How current are your test reagents? If they’re too old, maybe that could throw off your test results?

 

[Casey]

Add the recommended CYA to get to 30ppm and start SLAMing based off the 30ppm. Throw the sock in the skimmer basket and keep the pump running.

 

[jandersen13]

Brand new this year

 

[IceShadow]

Keep in mind that the core tenets of pool care here involve maintaining chlorine levels - an elevated level when SLAMming, and then a standard level when not. The term “shock” implies a one-time massive addition of chlorine which isn’t what is done here.

 

[jandersen13]

So I added stabilizer (4 pounds) 2 nights ago and then added liquid chlorine, 60 oz. checked the next day around noon and there was 0.5 chlorine. Had 10 kids swimming yesterday for 2 hours then added 128 oz of liquid chlorine last night. Checked this morning and see the chlorine around 0.5 again. Any ideas?

 

[JoeSelf]

You need to SLAM like everyone said. SLAM Process

 

[jandersen13]

I understand that. What I’m saying is that I started that last night. Is it normal to add enough liquid chlorine at 10pm to raise to proper FC shock level and then have 0.5 chlorine at 7am the next morning?

Water is clear but wondering what I’m doing wrong here.

Looking for some help...

 

[mknauss]

You are doing nothing wrong. You need to follow the SLAM Process to eradicate the algae. The chlorine you have added does that but then it drops too low and the algae grows again.

 

[Casey]

You're killing the algae and bacteria in your pool. The fact that you're losing so much chlorine at night indicates that you have an active algae bloom in your pool that the FC is fighting to eradicate. It means you have to keep SLAM'ING until you can hold chlorine at night, through the night. DO NOT STOP!

 

[jandersen13]

Ok thanks! If the water is remaining clear does that mean I’m getting close at least? I’m only able to add in the morning and night. Will that be ok as well?

 

[mknauss]

Any chance you can add three times per day? Morning, right when you get home from work, and right before bed.

No one at home mid day to add some chlorine?

 

[jandersen13]

Ah yes I can add first thing in the morning, evening and before bed.

Each time I need to add I need to test for FC though right?