Unable to properly flush holding tank for winter

Jun 1, 2007
O'Day 322 Mt.Sinai
I have not yet been able to flush my holding tank for the season (~16 gal tank, PH II). I pumped it out in early fall, then didn't use the head again. I'm storing the boat in the water this winter. I've been out of town returning next week, but the water has been shut off at the marina, and pretty sure the pumpout nearby is off now as well.
I guess my only option is to add some Odorlos, and winterize by pulling some pink stuff through from the inlet hose at the through hull.
Maybe every 4-5 weeks repeat till things open up in April or so?
Any suggestions?
Mar 3, 2003
Hunter 356 Grand Rivers
It should be ok if you do that. Make sure you get the pink stuff in the inlet line and into the lines to the holding tank. Flush some pink stuff into the holding tank. Leave pink stuff in the bowl. That's what I do in Tennessee and just start using the head in the spring and pump it out when you can.
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Sep 15, 2013
Catalina 270 Baltimore
If you pumped out your tank and haven't used it since you should be good to go. Just pull the hose at the intake seacock, stick it in a bucket of pink and pump it all the way through the system and into the tank. That works well for me.


Mar 16, 2010
Beneteau 411 Oceanis Annapolis
Yeah, pull some AF through the raw water intake hose to winterize the effluent hoses, if you have an overboard discharge seacock you will need to backflow some AF through it to make sure you don't freeze and crack the fitting. When done, disconnect the head discharge and intake hoses, drain the bowl and leave the system to dry out. I like to tape the lid down with blue masking tape as a sign the head is out of use. AF is a nutrient, so add a good shot of Odorlos into the tank to keep it aerobic.
Dec 25, 2014
Catalina 27 Pasadena, Md
I guess I have it pretty good, with my 1986 Catalina 27 they plumbed it so I can flush with seawater using open seacock, or closing seacock run fresh water, or in this case AF, into the sink and use that to flush through to the holding tank. No unhooking hoses needed. As mostly being a day sailor, it keeps things cleaner than flushing with sea water, and just fill the freshwater tank a bit more often.