this is one I haven’t thought of, what does one do at the end of the season with the holding tank. I can pump it fairly clean with the whale, however there will be a bunch of residue left at the bottom, I can flush with water however I don’t think its going to be perfectly clean. Whats the answer for winter storage and just general cleanliness.

On Zygote, our answers are:

  1. Flush the tank with clean sea water and then, when at dockside, with freshwater;

  2. Make sure the vent to the tank is clean and clear - bad smells are associated with anaerobic bacters, the sort that don’t like lots of air;

  3. Add a little of Raritan’s K.O. Kills Odors (see ) a solution that supposedly contains aerobic bacters that chew up any organic material and leave the head system sweet-smelling. Note: Use of K.O. requires that you not use bowl cleaners other than Raritan’s C.P. Cleans Potties.

K.O. is what’s called a ‘bioactive’ treatment, the idea being that the aerobic bacters crowd out anaerobic bacters. Along the lines of eating live bacter yoghurt, so that Lactobacillus spp. bacters crowd out other less welcome gut fauna.

Alternative to 3.: Functional equivalents to Raritan’s K.O. include products such as Headenzyme. Headenzyme is an ‘enzyme’ treatment in contrast to the ‘bioactive’ treatment of K.O.

Both ‘bioactive’ and ‘enzyme’ treatments are more expensive than (a) doing nothing other than a few more freshwater flushes; or (b) using a chemical/deodorant treatment. Some chemical treatments, such as flushing with formaldehyde, are very effective but also environmentally unfriendly.

Zygote has not had a problem using either ‘bioactive’ treatment or, on occasions, just flushing liberally.



That’s very good advice from Bil , tryed and true , I would say, that is !

Long time ago I found it important to have good access to inside of every tank onboard.

The two bilge installed water tanks have top access, the fwd holding tank has top access too. The engine room bulkhead mounted fuel tank has access through the forward side mounted access plates either side of the baffel.

What was great improvement was the enlargement of the holding tank overflow to a 3/4" hose and vent fitting to accomodate that.

It is quite easy to put chemical in the Lavac head and pump that through a full holding tank, thus purging the holding tank of residule odors, and steralizing the left over sticky stuff, still in the tank corners.

To lay up the holding tank , the only way I know is to mop it out, as best as you can, with chlorox , with appropriate injested libation during or just after the process .

I too looking for more creative ways , standing by for your most deep secrets !

Iduna is fitted with a Lavac head. In port, I flush the head with 1 gallon of fresh water, pump the bowl as dry as possible then pour 1 to 1 1/2 cups of vinegar in the bowl. In addition, we leave the lid up to ensure anaerobic bacteria does not grow in the bowl. I also replace the head hoses every 3 to 5 years.

For winter storage on the hard or in the water, we flush the holding tank with fresh water and pour 1 gallon of antifreeze through the head into the hold tank. The head never smells.

Thanks everyone the time has come when I have to dive in and do my thing, the exposure of your innermost secrets has been most illuminating we shall endeavour to be as clean on the inside as we are on the outside. No one ever talks about these issues and I am so relieved now that we have had a clean sweep. All kidding aside thanks everyone.

I mostly ignore the holding tank during winter haul-out. I simply have it pumped. Pump-outs around here tend to include a quick fresh water rinse.
I do pump RV antifreeze through the head and all the plumbing. The antifreeze pumping process leaves around a quart of antifreeze in the holding tank for the winter. I use RV antifreeze from Walmart (cheaper than marine anti-freeze).

Last winter I installed a Groco SSC flush fit on the engine raw water intake to make the antifreeze pumping process easier. This winter I’ll do the same thing on the head’s intake valve.