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Old 11-12-2018, 12:58 PM   #1
2 Rivet Member
2012 27' FB International
Austin , Texas
Join Date: May 2015
Posts: 55
Winter's almost here: ok to add antifreeze to black water tank?


We are currently dry camping in front of my brother-in-law's house in Dallas. The next 3 nights are predicted to be below freezing and I have no way of emptying the black water tank, which we've been using sparingly at night. My wife thought of adding a small amount of antifreeze to the black water tank so that the freezes don't crack the tank. Is there any reason I shouldn't add antifreeze? If I can, how much would you recommend adding?

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Old 11-12-2018, 01:13 PM   #2
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2012 27' Flying Cloud
W , New England
Join Date: Oct 2012
Posts: 7,402
Winter's almost here: ok to add antifreeze to black water tank?

Iím not sure my expertise is sufficient to effectively answer this question - but Iíll attempt something for your consideration and trust others will have better advice to follow....

1) How full is your tank? The freeze issue is expansion so for starters, unless youíre at 85+% capacity, I donít think the tank is likely to crack.

Adding a gallon jug or two of AF (again, depending on how full it is) might give you some peace of mind and shouldnít hurt anything - when you winterize and run AF through the toilet flusher, some makes it down in to the tank to get flushed out when dewinterizing next season.

2) below freezing for 3 nights - how far below and is it only for a few hours at night and back above freezing during the day? I think if youíre getting down to say 30 for 6 hours overnight and then above 35 during the day, youíre not likely to have much of a problem.

3) are you staying in the trailer during the freezing temps? If so, depending on year/model, running the heater will ensure some hot air gets to the rest of your pipes which is what Iíd worry about more than an unfilled black tank.

Having said all this - whatís the reason you canít just dump the tank? If youíre near a campground or a Cabellas or even some highway rest areas so equipped, you might be able to make a quick trip and ease your mind a bit. If youíre staying at a house that has a clean-out for the sewer, thatís a possibility too.

Just some thoughts and suggestions. Sadly, this free advice is worth everything youíve paid for it so take with a grain of salt and see if more experienced folks correct anything Iíve said here.

Good luck!
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Old 11-12-2018, 01:14 PM   #3

2003 25' Classic
Houstatlantavegas , Malebolgia
Join Date: Jun 2007
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Just keep it empty & you won't have anything to freeze. 😂👍

Iím done with ĎadultingíÖLetís go find Bigfoot.
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Old 11-12-2018, 01:15 PM   #4
Half a Rivet Short
2017 30' Classic
2022 Interstate 24X
Carlisle , Pennsylvania
Join Date: May 2017
Posts: 15,908

The sewage tanks are actually a fairly small risk in the event of a freeze. The big issues are the valves and other items in the main plumbing. The city water input anti-backflow valve is hanging out in the cold air so it's pretty vulnerable. The low point drain valves are under the trailer so protected a bit. With wind from the wrong direction .... they can be an issue.

One "simple" way to dump the black tank is to use a bucket and run the result into a toilet in the house. Yes that's a lot worse than the normal process with a hose....

In terms of "how much", you want about 1/4 of what's in there to be anti-freeze for modest temperature drops.

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