Forum Discussion

silverbullet555's avatar
Oct 26, 2020

Blue water in black tank - does it freeze?

We bought our camper in the spring and have not put water in it at all. The black water tank has some blue water in it from the previous owner.

It's cold now. Does that blue water have any anti-freeze properties in it or should I put some potable RV antifreeze in the tank? I'm not using the toilet. Would it be better to just drain it and leave it dry?

20 Replies

  • mkirsch wrote:
    Unless the tank is right full where the water has nowhere to go when it expands it won't cause a problem when it freezes.

    The freezing temperature of blue water is lower than regular water but nowhere near as low as the pink stuff.


    Depends on who's blue water it is....I've heard no splash at well above zero and close to freezing sometimes! lol
  • Wow, that stinks (not literally) bought a new camper and didn't get to use it once?

    If it's blue juice like porta pottys, it freezes in Idahoo.

    I use windshield washer fluid generally for all my tank/p trap winterizing on boat and camper. Usually because it was cheaper.
    Just walking through the farm supply yesterday, both were on display for the same price, lol.

    Since you don't know how much blue juice is in it, I'd dump it first to be safe, although you escaped the arctic blast this weekend, but not tonight maybe.

    Unlike the post above, hopefully they didn't fill your water lines with pink stuff, yuck, but have you confirmed that it's winterized?
  • I suspect the previous owner winterized the P-traps and black tank with windshield washer fluid (the sub-freezing type). If you can contact the PO and confirm that, I’d just leave it.

    Hopefully the fresh water lines have pink RV antifreeze in them.

    :):)
  • Unless the tank is right full where the water has nowhere to go when it expands it won't cause a problem when it freezes.

    The freezing temperature of blue water is lower than regular water but nowhere near as low as the pink stuff.
  • If the blue water is actually RV antifreeze then yes it can freeze but does not expand and will not cause damage.
    If the blue is plain water with a blue deoderizer then it will freeze about same as water.
  • Best to drain the tanks if you can . Put some pink stuff in all the traps so odors don’t come up from the tanks . If you haven’t used the water since it was winterized you’re all done .
  • No that blue water will freeze. Usually not an issue because it has plenty of room to expand in the tank and shouldn't cause any damage. Best is if you can drain it and add some pink stuff.
  • midnightsadie wrote:
    if you can empty the tank. then I pour a gal of rv antifreeze in mine . if you can,t empty? pour two gal in just to be safe. rv antifreeze is under two bucks a gal here. drive around the block to mix.


    I have some here because I just winterized the boat.
  • if you can empty the tank. then I pour a gal of rv antifreeze in mine . if you can,t empty? pour two gal in just to be safe. rv antifreeze is under two bucks a gal here. drive around the block to mix.