The Skipper's Blog

Ask The Skipper
Views Counter

Can I mix Odor Free with Thetford’s Aqua-Kem in my holding tank?


Shirley Steele asked:

Hello ~ I stumbled onto your website in an internet search about winterizing…

Regarding Odor Free, is it okay if it mixes with Thetford’s Aqua-Kem in the tank? We like Aqua-Kem but I’d like to try something else and Odor Free has such great reviews, plus I read about the “cocktail” of Odor Free and antifreeze for winterizing…

We have a houseboat on a lake at a marina in Virginia USA that will stay in the water. We cannot get the wastewater tank pumped out until after winter (the dockside service only runs Memorial Day to Labor Day) so there is waste, water and Aqua-Kem in it now. It is an 80 gallon tank, no idea how much is in it. We put a cup of antifreeze down the toilet into the tank today which I am thinking probably isn’t enough -?

Thank you!


For your convenience, I’ve highlighted the hyperlinks. Click on the hyperlink to get more information about the selected product.

According to the Aqua-Kem MSDS, it contains Formaldehyde, which is a carcinogen and Methanol which is hazardous, so it’s probably wise that you change to another holding tank chemical and get you tank pumped out at you first opportunity. These chemicals are quite volatile, which means that it will fill your boat with fumes which you and your family will inhale.

Our senior chemist doesn’t think there will be any adverse reaction between the Aqua-Kem and Odor Free, so you should be OK to add that to control the odor. Depending on how full the tank is and how cold it gets in the winter, I suggest you will probably need 1/2 to a full gallon of antifreeze. I suggest that you use the plumber’s variety as opposed to the automotive stuff. It’s more environment friendly and won’t damage the plumbing. If you use automotive antifreeze, the pump out facility may not pump your tank as it is not environment friendly and may have to be disposed in a hazardous waste facility.

Because of your unique situation, I suggest that you use a full 22 oz. bottle of Odor Free, to get you throughout the winter. You can mix the Odor Free, with the antifreeze and flush it into the holding tank through the toilet. That will also help neutralize the odor causing bacteria in the hoses. When you pump out your tank in the spring, be sure to pour water down the hose from the deck fitting and pump that out to give you a head start on the season. The Odor Free, will loosen up any sludge in the tank so that it can be pumped out and the extra flushing is a good idea. After, use Odor Free, throughout the season. Just follow the instruction on the bottle or check the Ask the Skipper blog for other tips and tricks.

If you have odor coming up through the toilet or if the hoses are starting to smell, I suggest that you also pour a bottle of Odor Free Storage Treatment,into the toilet and flush it into the tank. It’s designed to cling to the plumbing and hose surfaces to keep the odor at bay for up to 6 months. It’s water soluble so when you flush the toilet in the spring, the water will wash it into the holding tank so it can safely be pumped out with everything else.

Thanks for your question.

Captain Aurora
Richard Kittar

The Skipper Recommends:
More Info
More Info
More Info