Green Algae, nothing working.

[chrisb]

We have had a green pool since July 5th, minimal changes.
24,000 gal. in ground vinyl liner cartridge filter.
Color is green, can't see bottom, walls are NOT slimey but we can just about make out debris on the bottom (shallow end) that is brownish and when disturbed "poofs" away. (Mustard??)

Treated with Bio-Spot, shock, no change
Treated with Banish, five bags burn out, no change
Treated with liquid chlorine, no change
Treated with Erase, no change
Treated again with Banish, 6 bags burn out the color of green diminished slightly from bright green to dull green. It has been 5 days since this last treatment and no changes. We are running the filter 24/7 since July 5th, washing the cartridge twice a day (not seeing the magnitude of debris you might expect). Brushing, running the Aquabot and maintaining proper chemical levels. Dispite the massive chlorine being added, the levels are staying in range, slightly above. Backwashed about 2 feet of water over this time. Even the pool people are shrugging their shoulders. They keep blaming it on the cartridge (vs. DE) filter. Saying it takes excess time because of this.
Any hope/help to salvage the summer??? We are located in NJ.
Thanks!

[Guest]

Post the numbers you have for the chemical balance of the pool.

If you don't know the CYA level then have the pool store check your level. If it is very high you may not be reaching "shock" levels in relation to your CYA level.

[chrisb]

After finding out we were overloaded with phosphates and more shock treatments the pool is now blue/gray/green tinted, cannot see the bottom.
Best it has looked in over a month, but far from clear.

Free 4.3
total 4.7
combined 0.4
ph 7.9
hardness 160
alkalinity 108
cya 40
copper 0.06
iron 0

We were advised to do more anti phos since it is at 500, lower ph and shock again. We are vacuuming daily and washing catridge daily. We were also advised to pour a lb of DE into the skimmer to help trap particles in cartridge.

Comments appreciated.

[chem geek]

The phosphate remover is a great way of transferring money from your wallet to the pool store. It's not that it won't work, but that it isn't necessary. To clear a pool of algae, you simply need to MAINTAIN a shock level of chlorine, regularly brush, and clean/backwash the filter. In the worst case with a pool that has terrible circulation (such as many above-ground pools with no floor drain) then a flocculant can be used after the algae is dead and then vacuum to waste (assuming that can be done).

If the numbers from the pool store are correct, then with a CYA of 40 you should raise the FC level to 12 ppm (15 ppm would be fine) and keep adding chlorine to hold it there. Before you do that, however, you should lower the pH since it's too high -- lower it to at least 7.5 though you could go down to 7.3 since you will be shocking the pool. To shock the pool, use either 6% unscented bleach or 10%/12.5% chlorinating liquid or Cal-Hypo (the latter adds to Calcium Hardness, CH, but yours isn't too high so that's OK).

You can read more about clearing a pool of algae in this link.

Richard