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countrygent5201 11-13-2009 10:17 PM

Stench from Fresh Water Holding Tank
The previous owner of my 1986 Hunter 28.5 stopped using the fresh water holding tank several years ago, but apparently didn't completely drain it. Since I'm one who believes a thing should be used if it's there, I filled the tank with fresh water from the dock system and later attempted to use it for hand-washing after a visit to the head. At first, the water seemed normal, but then a stench began to develop as the water ran. I immediately began draining the tank by opening both the head and galley faucets, and the odor became really bad -- a rotten egg sort of stench -- as the last few gallons were pushed through the lines. I flushed the system for about 10 minutes, then dumped in a box of baking soda and refilled the tank. Little if any improvement. Next I tried a cup of chlorine bleach. Still stinky. I'm sure the stench was caused by allowing water to stagnate in the tank, but how do you get rid of the awful smell? I don't intend to drink the water or use it for cooking, but it even leaves your hands smelly after washing them in it with soap. Is there a product that eliminates the stench. If I can ever get the tank clean again, is there a rule-of-thumb about how often it should be drained and refilled to avoid stagnation?

night0wl 11-14-2009 12:10 AM

Have the same issue in my boat...but dont know how to fix it. Advice is appreciated!

mitiempo 11-14-2009 01:46 AM

Put a fairly strong bleach solution in the tank, much more than a cup, maybe a gallon in a 25 gallon tank. Let sit overnite. Drain tank through taps. Repeat if necessary. Check the hoses to the taps - they probably need replacing anyway - after all they're probably original. Then just fill and drain until the bleach is not apparent. It worked in my case and the tank hadn't been used for over a year. I replaced the lines as they were black with age and probably as old as the boat - 32 years.
ps - then you only have to get rid of the smell of the bleach.

roline 11-14-2009 08:07 AM

Ah yes the old Hydrogen sulfide from bacteria. I had a touch of it and couldn't figure out why. I had removed the poly tank and bleached it, replaced the lines and after a season started to have it again. I realized that the tap water that I was adding was from the kitchen sink has a carbon filter that absorbes all of the clorine in the water. SO there was a lack of treatment for bacteria. Bleach (hypochlorite) works well. Another treatment that can be used is Hydrogen peroxide, but do not mix the two!
Hydrogen peroxide sanitizes without the bleach stench but is more expensive to use. Once under control, sanitize at least once a year.

sailingdog 11-14-2009 10:47 AM

First off, I would highly recommend opening the tank's and pressure spraying the interior if at all possible, then I would replace the hoses and finish by shock treating the whole system per Peggie Hall's directions.

Bleaching or treating the lines won't work very well, since the lines probably have a bioslime coating, where the bleach only affects the outermost layer of it, and doesn't kill all of the bacteria/mold living in it.

I don't recommend adding chlorine bleach to the fresh water system as a matter of normal use, but shock treating it once a season is a good idea.

countrygent5201 11-14-2009 10:55 AM

Roline, how much peroxide should I use? This sounds like the best route if it doesn't leave its own stench. Would a quart per 25 gallons of water do the job?

scottyt 11-14-2009 12:39 PM

gent you should go to a pool supply or a wood working place and get the peroxide there. it will be stronger, so you need less, but make sure to dilute it in some water before dumping it in.

if you use anything you will need to remove any screens in faucets as they will clog as the slime come outs. what i would do is shock it with bleach, a couple of cups, and run the faucets till you smell the bleach. let it sit over night, then drain completely. then repeat, the same then a couple of flushes to clear it out. once you do this open the inspection port if you have one, the bleach smell will go away in a day or so with the port open

Faster 11-14-2009 12:59 PM

Just an additional comment, when you shock or bleach your tanks you should be sure to completely fill them each time to ensure you're getting the bleach/peroxide to all the inner tank surfaces.

wookie 11-14-2009 01:06 PM

yea bleach works put plenty in leave 24hrs, drain through all taps, refill fresh water should work

mitchbrown 11-14-2009 01:07 PM

RO machine can make water smell like sulfure
If you have a Watermaker on the boat and they pickled the thing and then didn't flush it well enough before putting the product water back to running into the tank the chemicls will make the water smell like sulfure. The solution is to just flush the thing out really good and I would apply bleach and then flush again after 24 hours and then use it.


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