Algae

[sophiamia]

Hi,
Recently returned from vacation and found a bad case of algae in my pool. I tried treating it but decided to go ahead and drain to prepare for acid wash and some light sanding. Will the algae return as soon as the pool is refilled, or does it die without water.

[chem geek]

It will return if you don't add chlorine to the water when you refill. Even if you killed all the algae and then drained the pool, algae can get reintroduced very easily from the wind -- it blows in from any moist area with sunlight. So essentially, just think of algae always potentially being in your pool and that without chlorine to kill it, it is more likely than not that it will "appear".

So when you refill your pool, just add some chlorine to it (probably some Dichlor since that's stabilized chlorine that dissolves quickly -- just keep track of how much you add since for every 1 ppm FC you add, you also get 0.9 ppm CYA). The good news is that it takes algae 4-8 hours to double in population so you can add the chlorine at the end of a day of refilling and you should be OK -- even adding it the next day is all right. It's letting a pool got for more than a couple of days without chlorine when you'll notice it turning "dull", then hazy they cloudy and then into a green monster.