Green Algae = Swamp Hell

[shaggy911]

I have a 22k gallon inground pool. I am not an experienced pool owner, but i have kept it sparkling clean every year. This year i am very busy and now I am looking at a green swamp. I am worried that this will turn into black algae and i will never get rid of it. Please help advise so i can let my kid enjoy the pool before it starts snowing

I didnt open the pool until this week. There was a swamp over the 1" submerged pool cover. I bucketed the layer of algae out as much as i could and after an 1 hour I poured it into the pool, which was green anyway.

I took the water to local pool store and they suggested i drain it to half and refil.

I drained it to about 1/3 twice since on both occasions it did not do much good.

I incorrectly ran the filter for 4 hours and then backflushed it : the drain water was dark green. It was back flushed to light green and i left it off the filter. I just replaced my filter (Sand dollar 80) and pump (pentair whisper flo - high flow rate ). I am worried i may have damaged the filter media.

After the drain i did a analysis.

Saturation index 0.8

TDS 400

CYA 0

Tot Chlorine 0

Free Chlorine 0

Ph 8.4 - added Muriatic acid later

Tot Alkalinity 112

Tot Hardness 156

Optimizer+ 0

I added 1 gallon of Muriatic acid. I did not expect 4 pts would do much good.

i was recommended to use power floc. I did this and used the entire bottle (double the dose). I have waited for 12 hours now and it doesnt look like Power-Floc did any good - it was supposed to settle all the algae to the floor but i see it suspended. Or maybe there is so much algae that some is still floating.

I dont know why the store did not recommend to chlorine it aggressively. They werent sure about power floc and i would like to get more opinions rather than guesstimate at this point.

In any event I have a dark green pool with algae visibly floating (like slush ice in winter).

MY Plan:: Feel free to point out better approach

i have a gunnite pool

day 1:

vac to waste as much as i can

add 2 bottles of Banish (3% copper algaecide; light green algae dose for which is 1 bottle)

QQQQ: Should i add more?

recirculate the pool for a day (with the pentair i have it should take 4 hours to recirc the entire pool )

day 2:

Chlorine the life out of it!!!

12 lbs lithium hypochlorite. I will pre-dissolve it with a power drill driven mixer; apply from the skimmer at a slow rate of 2 lbs per 2 hours. My pool floor is white/slightly blue.

QQQQ: Will lithium hypochlorite be sufficient? It has 47% free chlorine. Should i try Cal-Chlor and risk higher Calcium levels? Seattle water is very very soft.

day 3 and 4::

Analysis to ensure that i maintain high chlorine.

QQQQ: What ppm of free chlorine should i maintain ?

Repeat day 1 to day 4 until I prevail over Algae.

Please post your recommendations. I know i should have been on top of maintenance, lesson learned.

[PoolGuyNJ]

NO ALGAECIDE, especially ones containing copper. Algaecides don't kill, they help prevent. Chlorine kills. Shock it to start killing the algae.

Hit it with 5 pounds of cal-hypo granular, three in one shot in the morning and 2 more later in the day.. Lithium is quite expensive and since you have a low CH, the cal-hypo will add some for you. Its cheaper too. Run the filter 24/7 for now. Lets kill the algae first. After 24 or so, it relaxes its hold on the surface it adhered to and makes vacuuming easier. The chlorine level will also have dropped.

Don't brush! That would put everything in suspension and possibly make particles that are too small to be easily filtered.. Save that task until you are close to finished.

Vacuum to waste. Start at the shallow end. Move fairly quickly and don't try to be precise. Lets get the mass majority first before you run the water too low. This may take more than one session. Your hose to fill the pool should be on.

I'll bet the pH is about 7 now. You added quite a bit of acid. If you pool is as swamped as I think it is, getting the pH, Alk, and CH levels will wait until you get the algae out. Vacuuming to waste will just blow out any chems added so don't worry over them yet.

Scott