This seemed impossibly horrifying to me, considering the amount of work I had put into ensuring that they would remain open.
I was at my wit's end. Heating the drain lines was out of the question.
I have to confess that I'm possibly grasping at straws, but I wondered if perhaps the problem is one of flow. If the water isn't getting out of the lines very promptly, it is freezing up in the twenty and thirty below conditions we have been experiencing for the past two months.
Looking again at my poly pipe drains with a critical eye, I can see that there were sections with steep drop, and some with shallow drop. As much as I worked very hard to keep a constant downward slope, it was nearly impossible to accomplish with the flexibility inherent in this type of pipe.
The other consideration was each coupling. Although the pipe is nominally one inch in diameter internally, each coupling reduces that to more on the order of five eighths or three quarters.
As such, I decided that the next course of action would be to replace the drain lines with ABS pipe instead of the polypipe.
I had hoped to be able to use two inch diameter piping, but home depot only had adapters for inch and a half piping. This also had the added advantage (which I didn't realize at the time) of being able to fit through the opening I had in the sauna footing for this purpose.
Dusting off my mathematics skills, I calculate that the cross section of my poly pipe was πr^2 - (22/7)(.75"/2)(.75"/2) = .45 inches. The cross section of the ABS pipe is (22/7)(1.5"/2)(1.5"/2) = 1.77 inches. I'm embarassed to say how many times I had to recrunch these numbers to be sure they were correct. In any case, as I could obviously see when comparing the ends of the two pipes, I was getting double or triple the flow through the ABS compared to the poly pipe.
The other big advantage of the ABS is that it is stiff. This means that I can get the optimal angle throughout the whole run of drain without fear of "dips".
Grandpa came over to assist, although he didn't volunteer to go under the sauna - he did pass me tools and stoke the sauna stove.
I went under, took various measurements, and then tried to make fit the pieces I had purchased.
Everything looked great until the very final piece, which was about a foot short to reach all the way through the sauna footing.
I opted to leave it for the moment. The hole through the footing still slopes down and away from the sauna.
I also opted to leave the pipes as a "dry fit" for now. I will wait until I have the whole system in place, and working properly, before I start glueing too much of it into a permanent positition.
Donna and Kenny were away at a session with Eric the Juggler. As soon as Grandpa confirmed that one drain had opened and was flowing through our new pipe, I was up and out of the crawlspace.
Grandpa and I poked and prodded at the remaining drain, confident that it would open after a short while of more hot water and patience. As soon as Grandpa returned home, I rushed to the cabin, grabbed my last clean pair of Y-fronts, and returned to the sauna to enjoy the fruits of my labour.
The other drain opened, and I enjoyed the warmth and ability to wash up, knowing the water was being carried away to be recycled by nature herself.
I overstayed my welcome. I spent over an hour out there until I saw Kenny and Donna out the window, and then headed back inside. Bliss.
It will remain to be seen if this is the final solution to my problems. I'm hopeful.
Addendum: Checking today, I can see that they are blocked by ice again. This is proving to be quite the conundrum.