Crack Craziness Page 2

Maintenance Q & A — September 2003
By Capt. Ken Kreisler

Crack Craziness
Part 2: Eliminating Tank Freshwater Odors
 More of this Feature
• Stress Cracks
• Eliminating Tank Odors
• PMY Tries... Aquapac VHF Case
 Related Resources
• Maintenance Q&A Index

I have an odor problem with a small freshwater tank onboard my boat. I have tried flushing it out many times, but it still smells. What can I do to alleviate this problem? J.B., via e-mail
You no doubt have algae, slime, or bacteria flourishing in your tank and lines. The easiest and quickest way to deal with this is to treat your freshwater system with a dose of bleach, which will kill whatever is thriving in your system. Simply pour a few cups into your water tanks and let it soak overnight. Check to see what impact bleach might have on any installed filters and make sure you flush the system thoroughly before using it.

But before dumping bleach-contaminated water into the surrounding waterway, check with your marina manager to find out the local requirements for proper disposal or contact the EPA’s Oceans and Coastal Protection Office for more information: (202) 566-1200 or visit The EPA representative I spoke with said that ideally you should dispose of the water onshore. Even though the small amount of bleach that would be diluted in the tank shouldn’t hurt the ecosystem, it’s better to put the mixture down a household drain, as that water ends up going to a water-treatment plant first.

To kill the odor-causing problem, fill the tank and add two-thirds of a cup of bleach for every ten gallons of water. Let that sit for a few minutes and then pump the tank dry, putting the diluted solution into another container you can carry onto land and pour into a household drain. Fill again as before, but let the tank sit full for about four hours before once again pumping it dry. One more four-hour sit and pump-out should do it. If not, let the tank sit full with the added bleach for 24 hours. After flushing it, keep filling and flushing the tank with fresh water until the bleach smell is gone.

Once you’ve gotten this under control, make treating your tank with a teaspoon of bleach for every ten gallons of water part of a monthly preventive-maintenance regimen. If your water tank is so small that this proportion leaves a smell to the water, cut the amount in half.

I also suggest installing an in-line water filter. Those made by Braun, Brita, and PUR will do and are easy to install. They can filter out any chlorine present as well as other substances that may add an unwanted taste. If you want to take this one step further, you can add a water-purifying tablet as directed to the tank. You can get these at most camping stores or large marine outlets such as U.S. Marine or Boat U.S. Also, when filling your water tank, make sure you are using a drink-water-safe hose and that all your connecting hoses are of the same quality.

If none of this works, remove the tank and have it cleaned and sanitized shoreside. And, depending on your needs, you may want to look into installing a watermaker aboard. HRO Systems has a unit that can fit boats as small as 25 feet in length. Phone: (800) 366-4476 or visit

Need help with a maintenance problem? Write to Maintenance Q & A, Power & Motoryacht, 260 Madison Ave., 8th Fl., New York, NY 10016. Fax: (917) 256-2282. e-mail: No phone calls, please.

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This article originally appeared in the August 2003 issue of Power & Motoryacht magazine.

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