I have a holding tank on rv, non potable water that I need to heat up to drain . I live in northern Alberta, so the average temperatures are -20. I don't want to wreck anything or gas myself out. I am looking for over the counter chemicals.

  • $\begingroup$ Ideas (1) Overnight in heated garage (2) Can you run RV long enough to get inside warm? (won't help if tank outside cabin space) (3) space heater inside RV like a kerosene heater. (again won't help if tank is on "outside" of cabin space.) (4) Since this is non-potable water might be able to dump car windshield washer fluid into system if there is any headspace in tank left. Might have to put warm fluid in, and siphon out since -20 is really cold. (too low for salt). (One gallon windshield washer fluid won't melt 20 gallons of ice...) // I'd worry that the freezing broke/cracked something. $\endgroup$
    – MaxW
    Commented Dec 23, 2015 at 3:14
  • 2
    $\begingroup$ Possible duplicate of Can you heat water with additives? $\endgroup$
    – Mithoron
    Commented Dec 24, 2015 at 0:30

1 Answer 1


I'm assuming you only need to liquefy ice to drain a septic/grey water tank. Calcium chloride (sold as damp rid) will melt ice down to $-56^\circ C$. Just add about 10 Pounds to the tank wait a few hours (perhaps even drive a little to slosh it) and drain.


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