Gas and Oil Home Heating Furnaces - Heating an unfinished basement

Hi,
I am hoping to prevent the water pipes from freezing in an unfinished basememt where the outside temp gets to -20. The water has been turned off and drained for the winter but I would like to be able to leave it on and had considered Heat tape (too many stories about fires) and a circulator. The piping layout does not favor a circulator. It was suggested that I install a vent-free propane heater but, am still not sure vent-free is safe. Has anyone had experience with these heaters? Or has anyone come up with the best way to keep the basement warm enough to prevent frozen pipes?
Thanks

Is this an empty house or do you live in it? What type of heating does the main house utilize now?

If you check it out the vent free heaters are outlawed in many states. Is there a furnace in the home that you can keep on?
I have used electric heat wire and electric tapes and it worked ;) ED

To follow up...It is a single story home on a 30x30 foundation. The only heat is a Propane fired 'Wood Stove' upstairs. In the basement is an electric hot water heater. I was looking into heat tape because I have read the newer ones were safe but, that can become as expensive as a new heater. I do know of someone who used a vent free stove in his home and the CO2 detector kept going off, so he got rid of it. Maybe a 'B' vent heater would be safer.

Thanks for your help,
steve

You can look around they have whats called a Direct Vent heater. this can just vent out a wall . It pulls in its own air to burn and vent. ;) ED