Light Green Spots - Algae?

[mbaskerv]

20000 gal in ground pool, vinyl liner, DE filter. Current readings : FC 4.0, CC 0.0, pH 7.6, TA 40, CYA 30, CH 25.
I keep the FC between 4.0 and 5.0, and although the TA is below what is recommended, I fell that since the pH is stable, there's not a need to add any baking soda.
I've been brushing the pool (floor and walls) daily since opening the pool about a month ago. My concern is that given all of the above, I almost always see a green patch or two that looks to be algae. It brushes away in small light green clouds, and doesn't appear again until the next day, not in the same places. The water is crystal clear, and the filter was backwashed last weekend, and filter pressure is a steady 10psi.
Should I increase my FC level, or could there be something else going on?

 

[mknauss]

If you have visible algae, you should follow the SLAM Process. It should go quickly.

 

[drsipe]

Sounds like the beginning of an algae bloom. You should start a SLAM, but if you want to do a verification first, you can do an over night chlorine loss test. That will verify the need for a SLAM.

The earlier you catch the bloom, the easier it is to knock it out.

SLAM - Shock Level and Maintain

We’ve all had to deal with a green pool. Clear algae from your pool with a SLAM! Read here to use shock level and maintain to clear your pool.

www.troublefreepool.com

 

[mbaskerv]

As recommended, started a SLAM Monday night at 12ppm FC. Ran overnight, Tuesday morning down to 11ppm. Boosted FC back to 12ppm Tuesday morning, brushed and vacuumed, FC down to 11.5ppm this morning. CC has remained at 0.0 and the water is clear.
I'll check it this evening after the sun goes down, get it back to 12ppm and do an OCLT tomorrow. Presuming that I don't go down more than 1ppm, I will consider this a win.
My concern is that we will be away this weekend, and I'm wondering if I should dump a few cups of chlorine in the water to "hold me over" until Monday?

 

[drsipe]

If adding chlorine is a concern, and you don't have an inline chlorinator,,,, and your CYA isn't too high, you could get a cheap floater and some Trichlor tablets to get you thru the weekend.

It would probably be better, if you could get a friend or neighbor to pour in 1/2 a gallon or so a day to keep the chlorine level up.

As a last resort, you could make a hillbilly drip system, by making a pin hole in the bottom of a bleach bottle, and get it to slowly drip the gallon into the pool. You have some time to experiment on the hole size and if a vent hole would be needed in the top of the gallon bottle.

I had worked in a very small sewage treatment plant as an operator, and our chemical pump dies on a weekend, and I was able to get us thru the weekend by making a hillbilly drip system, It's not perfect, and I overfed a little, but it worked.

 

[drsipe]

BTW, no offense to any hillbillys,,,,,, sometimes you just gotta improvise.

 

[mbaskerv]

BTW, no offense to any hillbillys,,,,,, sometimes you just gotta improvise.

 

[mbaskerv]

The FC was 11.5 last evening after the sun went down, and 11 this morning. CC has remained at 0.0 and the water is clear, so looks like my SLAM was a success. My CYA is only 30. I have an online chlorinator that I can put three or four "hockey pucks" of stabilized Trichlor into tomorrow before I leave. Based on the response, it's better to try and maintain a steady FC rather than boost it and hope it doesn't fall too low before I can test it and respond.
Thanks for the advice...TFP is the best