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Old 12-28-2020, 12:26 AM   #1
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Brand: Thor Motor Coach
Model: Chateau 31W
State: Delaware
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THOR #13591
Waste tank heater when empty?

Tried searching the forums but couldn't find my question.


I'm gearing up for camping over New Years Eve in northern Delaware, and the temperatures will be flirting with freezing. My black and gray tanks have heater pads stuck with adhesive to their undersides.



Is it safe to run the heaters if the tanks are empty? I don't know how warm they get, so I figured I'd better ask. I plan to be hooked to the sewer, but after dumping, is it safe to leave the heater pads running while the tanks are empty?


Many thanks!
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Old 12-28-2020, 01:30 AM   #2
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what do I know? - found this -

There must be liquid in the holding tank when you turn on the heater. If you turn on your RV tank heater while there is no fluid present, the heater’s damage could be significant. The heater, the holding tank, and the pipes connected to the tank could become damaged.

https://vancampinglife.com/when-shou...-tank-heaters/
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Old 12-28-2020, 03:47 AM   #3
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Quote:
Originally Posted by galOnTheGo View Post
what do I know? - found this -

There must be liquid in the holding tank when you turn on the heater. If you turn on your RV tank heater while there is no fluid present, the heater’s damage could be significant. The heater, the holding tank, and the pipes connected to the tank could become damaged.

https://vancampinglife.com/when-shou...-tank-heaters/

Wow, thanks for the link and info. I learned a lot. It still begs the question that if the pads have a thermostat, why would they cause damage to an empty tank? Wouldn't they just reach their temperature almost immediately and then cycle off?
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Old 12-28-2020, 04:01 AM   #4
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When you say flirting, how long will the temps be below 32? At 32, water will not freeze instantly but ice will melt. If you are going to be hooked up to sewer, your gray tank valve will be open, so no waste in that tank. No need for a heater. The poop and urine in the black tank will lower the freezing point of that fluid. If the overnight lows are in the low 30s but the daytime temps back to the 40s, I probably wouldn't turn the heater on for the black tank. This is what I do when camping in the winter here in Texas. My only concession is to disconnect the city water line.
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Old 12-28-2020, 04:21 AM   #5
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Originally Posted by Lt Keefer View Post
When you say flirting, how long will the temps be below 32?

We're expecting a couple degrees below freezing at night.



I suppose with warm gray water from showers and dish washing, no heater will be needed, and with the valve open, it won't build up.



We'll see about the black tank. If it gets colder than expected, I might use it. Personally, I'm just jazzed to finally get to try them out. The wires from the heating elements were hanging loose in the compartment when I bought the unit (yet another Thor factory defect that the dealer had to fix) so I don't even know if they'll work.
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Old 12-28-2020, 04:46 AM   #6
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Originally Posted by Lt Keefer View Post
The poop and urine in the black tank will lower the freezing point of that fluid..
On what basis? Only the residual heat, but that will not last to long, then there is the amount of sugars (maybe glycol) but that much would indicate your body is shot. Nope, it is all ‘water’ with a little salt.
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Old 01-01-2021, 02:30 PM   #7
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Quote:
Originally Posted by Choxnpinz View Post
Tried searching the forums but couldn't find my question.


I'm gearing up for camping over New Years Eve in northern Delaware, and the temperatures will be flirting with freezing. My black and gray tanks have heater pads stuck with adhesive to their undersides.



Is it safe to run the heaters if the tanks are empty? I don't know how warm they get, so I figured I'd better ask. I plan to be hooked to the sewer, but after dumping, is it safe to leave the heater pads running while the tanks are empty?


Many thanks!
Hope this is Lums. Only decent place in NDE. If so, take a ride around the corner (left as you exit, keep looking to the right) and check out the airfield.

And I would not run the pads on empty tanks. Why chance it? If there's nothing in there, what good will it do other than adding to the need to cycle your batteries?
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Old 01-01-2021, 03:33 PM   #8
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I was reading up on the heaters available and found something I never thought of... Please note, however, that adding a heat source to a gray water or black water tank may create excess gasses and odors. Like a slow cooker I guess.
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Old 01-01-2021, 03:39 PM   #9
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A thermostat controlled heating pad will not break/melt/damage your tank and especially won't damage pipes. How would pipes be damaged anyway? This is either a bad product or a scam if they expect you to watch Temps constantly and turn on and off a simple heater pad.

0/10 would not buy.
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Old 01-01-2021, 09:23 PM   #10
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Well I am curious as to the type control of the heat pads

On my previous rigs they were stick on 120v and you flipped the breakers on when Temps dropped

They didn't draw enough amps to damage the tanks if they were empty and you didn't shut them off right away
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Old 01-01-2021, 09:26 PM   #11
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Deaerateted water will freeze faster than water that is directly out of the tap

As you add solids that contain organic material the freeze point will increase

Quote:
Originally Posted by OldWEB View Post
On what basis? Only the residual heat, but that will not last to long, then there is the amount of sugars (maybe glycol) but that much would indicate your body is shot. Nope, it is all ‘water’ with a little salt.
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Old 01-01-2021, 09:32 PM   #12
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Originally Posted by OldWEB View Post
On what basis? Only the residual heat, but that will not last to long, then there is the amount of sugars (maybe glycol) but that much would indicate your body is shot. Nope, it is all ‘water’ with a little salt.
Salt will lower the freezing point, that is why they put it on highways and why you use it in an ice cream crank.
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Old 01-01-2021, 09:33 PM   #13
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So basically, if you take a huge dump (1 or 2) turn the pads on
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