Antifreeze in tolding tank - Cause of odors?

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Jan 7, 2011
5,630
Oday 322 East Chicago, IN
I pumped out the holding tank on my new-to-me 1996 Hunter 280 today. I took delivery of the boat from the PO in April and the level gauge for tank showed a little stuff in there, but not much. We have not used the head for much more than taking a pee, but we seemed to be getting an odor.

So I pumped out at the fuel dock today and saw thru the sight glass that the stuff was pink. I assume antifreeze from last season winterization.

Since Peggy stresses the need for air in the tank, I wonder if the antifreeze left in the tank could be contributing to the ordor (does the antifreeze "smother" the good decomp process)?

I looked through several "spring checklists" on the forum and did not see any that mentioned pumping the antifreeze out of the tank....so is the antifreeze left in the tank a problem or can it stay in there in the spring until the tank needs to be pumped out due to volume?
 
Dec 2, 1997
8,946
- - LIttle Rock
The solution:

You took delivery of the boat in April and you only pumped out for the first time in August??? And you're only just now beginning to experience any odor???

Make sure the vent is open...mud daubers love to build nests in vent thru-hulls, so scrape out the thru-hull with a screw driver blade or whatever works. Disconnect the vent line from the tank to check that end of the vent line AND the vent fitting on the tank for any buildup...scrape out what you find.

Now you're ready to pump out and thoroughly rinse out the tank. We've discussed doing that often enough that you'll find directions for rinsing out a tank in this forum.

All of the above should be done on a regular basis throughout the season.

Use Raritan K.O. or Odorlos (tank treatments), making sure to FOLLOW THE DIRECTIONS. However, although the directions for K.O. say that you shouldn't have to add between pumpouts, the bacteria in K.O. can only live until their food supply is exhausted...iow, till they've converted what's already in the tank to an odor-free material. So as little as you're using the toilet, you will have to add more of any product at least once a week--possibly even more often...and you really should pump out and rinse out once a month during the season.

If you continue to have odor out the vent, it may be necessary to do a little surgery on the system to increase the ventilation to the tank.
 
Jan 7, 2011
5,630
Oday 322 East Chicago, IN
Thank you for all of the good advice. I have been cleaning out the vent through hull as recommended in your book and on the forum. Lots of spiders at our marina this time of year and they get every where. I am sure the thru-hull vent cap is a prime spot for hthem.

I will start pumping out and rinsing the tank more often. I did not realize it had to be done until the tank was near-full.
 
Jan 7, 2011
5,630
Oday 322 East Chicago, IN
Re: The solution:

Forgot to ask for a clarifcation of my original question though.....does leaving the antifreeze in the tank at the start of the season cause any particular problems - Should it be pumped out before the head is used at the start of the season, or can it stay in there for the first month or when the tank needs to be pumped out (whichever comes first)?
 
Dec 2, 1997
8,946
- - LIttle Rock
Start the season with clean plumbing...

Compare it to getting ready for the first day of school...you wouldn't leave a whole summer's dirt on ya, you'd take a bath and put on clean clothes. So don't leave a whole winter on your boat and in the tanks, bilges, lockers etc IN your boat...clean it up, pump out and rinse out the holding tank. recommission the fresh water system, replace the joker valve in the toilet and lube the pump.

Or to put it another way...yes, the antifreeze should be flushed out of the tank in the spring. And your tank should be pumped out at least once a month....and rinsed out 2-3x/season, especially in preparation for winter layup.

"...first month or when the tank needs to be pumped, whichever comes first..." You don't use your boat much, do you? Or if you do, you certainly don't use the toilet! Fwiw, sitting unused is actually far MORE damaging to equipment than continuous hard use...'cuz rubber seals and gaskets dry out, lubrication settles and deteriorates, allowing internal parts to corrode...startups are VERY hard on anything that's rarely used. As little as your toilet is used, you'd actually be better off with a "MSD" portapotty (MSD version is designed to be permanently installed and is fitted for pumpout, so you don't have to carry it off the boat)...'cuz they don't have any moving parts to deteriorate. A 5-6 model holds 50-60 flushes...you might not have to pumpout but once a season...and then only to prepare for winterizing it.
 
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