Winterizing Black Tank Flush

[Dennis66]

How do you winterize the black tank flush? I have a 2021 303RLS

[StephenO]

From what I can tell, our black tank flush line travels vertically up to the vacuum break, and then back down to the tank. Because of this, and that there should be no long horizontal runs to hold water, I just use air to make sure it's clear. I have thought about buying a small hand pump to push some antifreeze through the line though.

Not to start the conversation about having a different hose for the black tank rinse and fresh water system, but I do have a separate blow plugs for the black tank rinse and the fresh water system. However, I have a separate hose that I use when dumping, that I know is not clean/sanitary since it has been used to rinse my sewer hose, and that hose end has been connected to the black tank rinse fitting. Because of that, I keep the two worlds completely separate.

[Canyonlight]

How do you winterize the black tank flush? I have a 2021 303RLS

Dennis - I bought one of these several years ago a year or 2 after we bought our 303. https://www.camco.net/hand-pump-kit-...ilingual-36003

Our Owners Manual does not state that winterizing the black tank flush connection/hose/back flow valve is necessary. Not certain what your manual states. Based on the design and installation (trusting the valve works as designed and there are no areas in lines where water can "sit") with our 303 and I trust most GDRVs, winterizing this s/n be necessary.

However, a few folks reported (not on GDRVs) that they had experiences on their prior RVs or heard of others who experienced possible frozen situations and thus broken back flow valves/lines/etc. As a result, I used this once and never used it again and have experienced no issues here in SD over 6 winters now.

Seems Rob Cate&Rob along with several others of us had a number of posts covering this good question over the years on the prior GDRV forum, not owned by GDRV. Maybe Rob will chime in or possibly others who may have feedback.

Dan

[Country Campers]

I do not think that it is necessary to winterize the black tank flush line but it is necessary to winterize the outside spray port on the nautilus panel. Using the outside spray hose connected to the black tank flush line you could winterize the black tank flush line.

Brian

[Dennis66]

Maybe just blowing it out with air?

[Cate&Rob]

Dennis66

In "theory" the black tank flush line should not need antifreeze because it is supposed to be a downward slope all the way from the vaccum break to the black tank and thus should drain. In fact, this line often drops below the tank flush nozzle and thus creates a low point that will hold water.

Not wishing to restart the "two hoses vs one hose debate" . . . but , the black tank flush is a sanitary connection as long as you always treat it as such. I simply take my outside shower hose and connect it to the black tank flush while winterizing, to fill any low points in the flush line with antifreeze.

Rob

[Dennis66]

great idea better safe then sorry

[KSC_Travels]

Dennis66 FWIW found this in my manual (p.100)

"When you are done adding RV antifreeze [per the Nautilus instructions]

9. BLOW OUT the black tank flush line at the outside connection with compressed air (max 70 PSI)."