First pool fail/green pool. how to recover?

[poolshrinker]

First year pool owner, and I’ve had my first fail!

About 1-2 weeks ago I started noticing some fine sand at the bottom of the pool. The vacuum didn’t suck it up well, but it was helping. Water seemed fine. Couldn’t tell where the sand was coming from, but we have a serious crow infestation around here and they like to land on the solar cover in the morning, so I thought maybe they were bringing it in or worse, it was their poop residue.

About 1 week ago I noticed the water was a little cloudy, and there seemed to be a little more sand.

Two days ago when adding chlorine, the water seemed fine. Sand seemed to be growing.

Then last night, opened the pool to add chlorine and there was a definite green tint. And my wife does a google search and discovers the ‘sand’ is probably algae...

So what happened? I think I got too confident in my predictive abilities and wasn’t testing the chlorine levels frequently enough. And admittedly, also probably fell behind adding chlorine, and let it get too low, for too long.

Last night I added a full gallon of chlorine (10%).

This morning the water looked slightly better, but still greenish. I tested the FC level and it was 5.5. CC 0.5. CYA 30. We backwashed the filter and tons of green water came out. I added another half gallon of chlorine.

This afternoon the water looks a little better. there is some algae on the pool floor that we’ll vacuum. FC is 10.0.

Am I on the right track? Just keep the chlorine going and vacuuming up the algae, and then eventually backwashing the filter as necessary? Do I need to do anything else?

Is it safe to swim in the pool now, tonight, tomorrow?

 

[mknauss]

Follow the SLAM Process

You can safely swim in a pool as long as the FC is above the minimum and at or below SLAM level based on your CYA. You must also be able to see the bottom of the pool in the deep end of the pool.

 

[poolshrinker]

thank you - if I don’t SLAM, and just keep FC where it currently is (10) without getting all the way to SLAM level, does it slow my progress or does it make it impossible to get ahead? I’m not opposed to SLAM, it’s not really more work than I’m currently doing, but I would have to add a little acid to bring the pH down below 7.5.

 

[mknauss]

Not sure I understand why you do not want to raise your FC to 12 ppm? You can still add acid.

Not taking your FC to SLAM level will make the process go slower. Up to you.

 

[poolshrinker]

ok, pool math calculator says to add 1 quart of MA to bring pH down to 7.4. Is there any reason I can’t add that all at once (in a pencil stream in front of the skimmer)? I am adding 31.45% hydrochloric acid, 20 baume).

Will that affect TA? To bring my pH back to 7.5-7.8 (normal), do I need to add baking soda or just wait? And it is ok to swim with pH 7.4, FC below SLAM? I can easily see the bottom of my 52” pool already - it never got too out of hand!

I’ve never had to deal with pH or TA before, it has always been perfectly balanced from the tap without additives of any kind.

 

[mknauss]

Add the acid to the pool return stream. No issue. It will have minimal effect on the TA. No need to mess with anything but FC after that.

You can swim as long as the pH is in the 7's, the FC is at or below SLAM level, and you can see the bottom of the pool.