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Old 18-10-2015, 18:17   #1
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Holding tank cleaning??

I use typical holding tank chemicals readily available in marine stores, but whenever i use my vacuflush toilet, pretty bad smell comes out the vent line. The tank is regularly emptied at pumpout station in my marina and level is low in it although I do not know how much of the tank volume is unpumpable. The boat is 1980 with original holding tank. Is there a chemical out there that can be effectively used to pour into the tank with the fresh water to try and dissolve the accumulated deposits on the sides and the bottom of the tank? My hoses are new, and i do not have bad smell in the boat. it is just when vacuflush is used that it smells bad as it pushes the contents of the hoses and vacuflush tank into the holding tank. Would a quantity of ordinary bleach and fresh water dissolve the contents and improve the condition?
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Old 18-10-2015, 18:53   #2
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Re: Holding tank cleaning??

If it is caked onto the sides and bottom it make take manual cleaning (ugh). You might try a product called Noflex Digestor. It is available from a number of online sources including Amazon and others.

Bleach will do nothing good for the holding tank so don't put that in there.

For the smell that comes out of the vent line (what you described) you can buy or make your own charcoal (aka carbon) filter. Carbon tends to absorb odors so as the vent expels the tank gases the smell isn't as bad. There are numerous online descriptions of making a carbon filter for the holding tank vent line.
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Old 18-10-2015, 19:45   #3
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Re: Holding tank cleaning??

(This is the same reply I posted to this question in the trawler forum):

Holding tanks should be at least nominally rinsed out after every pumpout or dumpout...thoroughly flushed out 2-4x year depending upon length of your season, and especially in preparation for winter or any other extended layup. It’s not hard to do, and all you need is water:

Pump out the tank, or dump it at sea. Then put enough water into the tank via the deck pumpout--becasue that sends the water into the tank at the bottom to stir up any sludge and hold it in suspension so it can be pumped out--to cover the bottom to a depth of 4-6”... it can be fresh water at the dock or sea water using a washdown pump. Pump out or dump... repeat...repeat...repeat...till you’re pumping or dumping clean water.

Human body waste contains animals fats which can build up on tank walls and clog tank gauge senders. So every year or two--or any time you’re preparing the boat for winter or other extended layup--it’s a good idea to clean out the tank. Follow the above instructions, then fill the tank with clean water and put a gallon (2 gallons if the tank is 50 gallons or larger) of liquid Tide, Wisk or any heavy duty liquid detergent and about 10 lbs of ice cubes into the tank via the deck pumpout fitting (not down the toilet!). Use “homemade” ice, not bagged ice...”homemade” cubes are larger and harder, so they last a lot longer. Go sailing and tack a lot, or go out on a day when seas are bit rough if you’re a power boat. Then, if you can, let it sit overnight. Pump out and also run some of the detergent solution through any macerator pump and related plumbing. Fill tank again with clean fresh water...pump out or dump and rinse out again.

Chemical holding tank products are cheap, but they don't work and they're about an environmentally UNfriendly as it's possible for anything to be. I suggest you try a product called Odorlos. Odorlos The active ingredient is nitrates which help to promote oxygen release from the waste (oxygen is key to odor elimination). It's a lot more readily available --not to mention a lot less expensive--from RV supply stores than marine stores.

Never use bleach in a sanitation system because it's destructive to rubber and breaks down hose resistance to odor permeation.

Vent line filters should only be used as a last resort because a) they actually help to create the problem they're sold to solve...and b) they're EXPENSIVE!
© 2019 Peggie Hall
Specializing in marine sanitation since '87.
Author "The NEW Get Rid of Boat Odors"
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