Algae Growth in a Toilet Tank

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Things You'll Need

  • Sponge

  • Spray bottle

  • Chlorine bleach

  • Toilet brush

  • Rubber gloves

  • Goggles

  • Respirator

  • Muriatic acid

  • White vinegar


Substitute white vinegar for muriatic acid if your house is on a septic system or you're concerned about flushing muriatic acid for any other reason. Vinegar isn't as strong, so empty all the water so the vinegar won't be diluted. Leave the vinegar in the tank significantly longer -- perhaps one or two hours. Flush once or twice when you're done. Vinegar is harmless to the pipes and septic system.

Periodically pour a cup of chlorine bleach into the tank, leave it for 15 minutes and flush -- this should keep the green algae and pink bacteria under control. The best way to control sulfur-reducing bacteria is to install a filter at the point where the water enters your house.


The fumes from muriatic acid can harm your eyes and respiratory system. Keep the lid on the tank while you're treating it with acid, and keep the bathroom well ventilated and the door closed.

If you notice a sulfurous odor coming from your toilet tank and a hairy, stringy growth at and below the water line, your water may be contaminated with sulfur-reducing bacteria. Green algae can also grow in your tank, especially if you live in a hot, humid climate. Not only that, a pink growth means your tank may be infected by Serratia marcescens bacteria, which can cause urinary tract infections. Algae and pink bacteria are tenacious, but you can control them with chlorine bleach. To kill sulfur-reducing bacteria, though, it's best to treat the tank with an acid.

Step 1

Image Credit: Jessica Shaw/Demand Media

Turn off the water to the toilet and flush to empty the tank. Sponge all the water out of the tank and transfer it to the bowl.

Step 2

Image Credit: Jessica Shaw/Demand Media

Put on rubber gloves, goggles and a mask. Spray the sides of the tank with full-strength chlorine bleach, and scrub them with a toilet brush. Keep the bathroom well ventilated while you do this.

Step 3

Turn the water on; let the tank fill, and flush. When the tank fills again, pour a cup of chlorine bleach in the water; let it sit for 10 to 15 minutes, and then flush. If your tank was contaminated by green algae or pink bacteria, you are finished. If sulfur-reducing bacteria are growing there, perform an additional treatment with muriatic acid or white vinegar.

Step 4

Fill the tank about half full with water, and then fill it to the overflow line with muriatic acid. Put the lid on the tank. Let the acid sit for about 15 minutes,and then flush 10 to 20 times over the course of an hour to dilute the acid in the drainpipes. Be sure you're wearing your rubber gloves, goggles and respirator.

references & resources

Chris Deziel is a contractor, builder and general fix-it pro who has been active in the construction trades for 40 years. He has degrees in science and humanities and years of teaching experience. An avid craftsman and musician, Deziel began writing on home improvement topics in 2010. He worked as an expert consultant with eHow Now and Pro Referral -- a Home Depot site. A DIYer by nature, Deziel regularly shares tips and tricks for a better home and garden at

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