Any good green ideas on what to do about frozen drain pipe for washing machine?

[IrishAyes]

After I moved here 8 years ago, one of the first things I had done was just about all the extra insulation there was room for. The walls have blown in insulation.

However, on rare occasions the washing machine drain pipe will freeze over after a long spell of near zero weather. I've always kept thermometers around the house, and the utility room stays at about 50 degrees all winter. Ground water used to come up under the house - very high water table here - but I had a drain installed there and we have to have massive rains for anything to accumulate under the crawl space in that one place at all.

However, the danged drain in the laundry room is stopped up again! I treated it with baking soda and vinegar over an hour ago with no luck. I've always been a little afraid of heat tape since it's been known to fail and start a fire. There's zero chance of the drain plugging up for any reason except an ice ball somewhere, because I keep a strainer on the washing machine's drain hose. Also, every faucet in the house goes on slow drip when it's 20 degrees outside or worse, and of course all the cabinet doors are propped open all winter. (No kids.) Right now the faucets have been on drip for about a week, 24-hours.

Maybe I'm just being too impatient. But does anyone else have reasonably safe ideas how to handle this? I simply won't use caustic drain cleaners, especially when it's just ice. If necessary I'll pour boiling water down there but I don't like carrying it back there because if I spilled it on myself....