Swimming Pool Blog
by Rob Cox August 2, 2013
How to Eradicate Algae from a Pool
Some pools never become contaminated, and other pools - have constant algae problems.
This post is for those pool owners who battle algae every year, and never seem to recover for very long before another algae outbreak takes over.
And also for those of you responsible for turning around a pool that has been neglected for months or years without chemicals or filtering.
Here's some ways to really fight back hard, and keep algae from coming back - ever again!
If you have had an algae outbreak in the last year, and by outbreak I mean algae everywhere, not just a small spot here or there - but maybe a green pool opening, or a hot summer bloom, then you still have the spores of algae in your pool.
Black, Green, Yellow algae - these strains can exist alone in your pool, or can share the habitat.
Black algae is the hardest type of pool algae to eradicate, due to its deep roots, but not impossible. For plastered pools, you'll need to replaster the pool, replace the filter media, and use a pipe cleaner to remove deposits inside of the plumbing. Replace all of your pool toys and pool cleaning tools - even your swimsuits, just to be safe.
Refill with fresh water after plastering, and balance the chemistry. Now that black algae has been eliminated, keep it from returning by using maintenance doses of a good pool algaecide, and a phosphate remover chemical.
Green Algae is the easiest to kill, but it's spores lay dormant, waiting for chlorine to get low, or food sources to develop. If you have repeated green algae blooms, drain the pool (vinyl pools drain only 1/3 of the way, refill, drain 1/3 again, refill and again drain 1/3 and refill). Pressure wash plastered pools (vinyl pools just hose off the wall).
For bad cases, such as neglected pools, after pressure washing the pool, you may need to acid wash a plaster pool. A chlorine bleach wash can also be done, but is highly reactive to acid, so rinse thoroughly in between washing with acid and washing with chlorine. (Vinyl pools can be drained fully only if you are able to reset it with a vacuum, and never use acid or chlorine, or a pressure washer to clean).
Replace your filter media (sand, cartridge or DE grids), and throw out any pool noodles, chairs, nets and brushes. If you have gear you'd rather not replace, give it a good soaking in a 50% bleach solution.
Refill the pool, balance the chemistry and maintain a good chlorine level. Begin using maintenance doses of both a high quality algaecide and a phosphate remover chemical.
Yellow Algae can be a frustrating strain to battle against. Difficult to remove, but it does loosen up it's grip with very high doses of chlorine. For this extreme algae eradication, we also drain the pool (vinyl pools should not fully drain the pool, or the liner may relax).
Pressure washing, and acid washing should be done on plastered pools, to really clean the surfaces, skimmers, and behind the pool light. Like the other algae types above, you should also replace your filter media, and any old pool cleaning tools, toys, floats and swimsuits.
After refilling and starting the pool, balance the chemistry and keep your chlorine level above 2.0 ppm. Add regular maintenance doses of a quality algaecide and also use phosphate remover 1-2 times per year.
Pool algae can take some work to eradicate it fully, so it won't come back, but having turned around many problem pools, I can tell you that these methods work. These are not cheap solutions - to replace filter media and water, and then start spending an extra $50-$100 per year on pool chemicals.
But, you'll enjoy not having to slay the algae dragon again.