Cleaning algae from a dried pool

Algae problems in swimming pool water.
Green (cloudy) water or slimy pool walls.
Black algae. Mustard algae. Pink or white pool mold.

Cleaning algae from a dried pool

Postby mlitsonata » Wed 04 Sep, 2013 11:37


I'm the new manager of a hotel that is in pretty bad shape. I'm working on the pool now. Not only was it a swamp but a lot of renovation work needs to be done to bring it up to code. The only thing that seems to be sound is the structure of the pool itself. It's going to be a while before we can get everything up to code and it was recommended that we drain the pool for now.

So I've drained most of the pool so far, it's still pumping, and now we have the nastiest algae mess I've ever seen on the bottom. I'm guessing the deep end could be a good inch think when it's done. Unfortunately I couldn't shock the water first to kill most of it because the pumps are all shot and need to be replaced.

So, my big question. What is the best way to clean up this algae? Some has dried on the first few steps and when I went to clean that up to get a feel for it I found that it seems to dry like cement! I thought I could just brush it away, haha, suuuure. I'm guessing I'll need to use a hard brush to loosen it up and then sweep it away. Talk about a lot of work! Any suggestions?

free info

Cleaning algae from a dried pool

Postby free info » Wed 04 Sep, 2013 20:15

get liquid chlorine and pour it from the tile down around the sides of the pool walls all the way around it let it stay on 5 mins or until algae turns color. Know its easier to pour using a plastic jug that you use to water plants just cut off the tip so it pours nice like a hose. Then gets the hose with a nozzle to help get all the dead algae off the walls then do the same to the floor. This all being done I assume with you using a sump pump I assume. Its called a chlorine wash
TSH Tech

Cleaning algae from a dried pool

Postby TSH Tech » Thu 05 Sep, 2013 22:02


I just want to add too Free Info's advice there, that the chlorine wash is what you need after you completely cleaned, shoveled, bucketed, all the solid algae mess out of the pool.
Keep in mind, you will want to perform a chlorine wash in the morning hours and not during the heat of the day. There's a few reasons for this; the first being, the chlorine fumes are strong, and will irritate the nose passages and lungs a little, enough to almost knock you down if you get a strong whiff. Second, the chlorine will not evaporate quickly in the morning. It will stay pretty liquid allowing the chemical to kill the algae.

A few safety reminders as you work with chlorine during the wash
- wear clothes you don't care if they get bleach stains
- wear nitrile gloves to protect your hands
- please feel free to wear a cartridge type respirator you can get at most hardware stores to protect your nose from the strong fumes. I find they work great and the fumes don't bother my breathing.
- goggles! It's going to happen. It will happen. Chlorine will splash in your eyes. No matter how careful you think you are pouring, *splash*, right in the eye.

have a garden hose with a high pressure nozzle handy at all times and have fun!

Re: Cleaning algae from a dried pool

Postby beemonkie » Sun 09 Apr, 2017 09:58

My kids and I tried cleaning the pool the other day. It has been sitting empty for 25+ years. Over the years it would get sitting water in it from the rains and ocassionally my dad would pump it. We are trying to buy the house and can't close escrow til the pool is filled and water "moving". Seriously a major waste of time, money and water because we are redoing the pool after we close escrow. My question.... Is the black algae harmful to breathe in as we clean it? I didn't think about it til after the fact and now I'm worried. I sprayed chlorine all over and let it sit over night before we started scrubbing and washing it.
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Re: Cleaning algae from a dried pool

Postby Denniswiseman » Mon 10 Apr, 2017 02:54

I have never heard of algae being harmfull or special precautations being taken other than to protect yourself from the chlorine used to kill it
If you do an acid wash Hydrochloric acid (Muriatic acid) on the other hand is noxious to breathe and get on your skin, surgical masks are ineffective you need a 3M 4277 or similar
I suspect that as the property is being sold with a swimming pool the mortgage company want to know that it's sound
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Re: Cleaning algae from a dried pool

Postby azulverde » Mon 22 Jan, 2018 08:08

You can weight it off with a powerless dye arrangement and after that draw it out with a sump pump.
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Re: Cleaning algae from a dried pool

Postby Teapot » Mon 22 Jan, 2018 17:23

azulverde wrote:You can weight it off with a powerless dye arrangement and after that draw it out with a sump pump.

I reckon you used a translator for that text? Well done for trying at least.

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