Well -- this bathroom of mine has been troublesome. The latest is a case of two steps forward and one back.
On 28DEC20- the plumbing company finally showed up to install the fixtures (not the shower cabinet -- that is another looong and ugly story). They installed the toilet and vanity/sink and then ran the water for 15 minutes to test for leaks and proper drainage. Not good.
First problem was water bubbling up from the into the toilet from the running sink.
They then unscrewed the Studor (sp?) valve head and we heard the bubbling and gurgling of running water. So the brand new valve was defective.
Then the assistant plumber yelled there was water gushing up through the shower drain (the base was installed weeks ago, still no cabinet walls)
Call in the pros with the $22K equipment to scope the drain line. Concerns included: roots in the pipe (unlikely), crushed pipe (maybe, but schedule 40??), broken joint (possible), ice (but from what water?). I didn't put much credence in the ice option cuz no water had run down the drain since it was installed (aside from the test the day before) except for condensation from the boiler (which heats the in-floor tubing and the domestic water -- how much can that be!)
The pros IDed the blockage as ice. But how? He looked at the specs of the boiler and estimated that since it has been warming the garage for the last ~2 months, condensation amounted to 1.5-2 gallons per day. BINGO
Photo 1 - clean and clear interior of drain pipe (4" diameter schedule 40)
Photo 2 - view at 66.5' down the ~130' drainage pipe -- you'd be hard pressed to fit a golf ball through there (*)
Gotta break up the ice. The pro has a serrated blade attachment to his b]cable but that would chew up the interior wall of the pipe. He recommended bales of straw to insulate the pipe and my GC added that I should buy a de-icer cable (like used to prevent ice dams on gutters). We'll attached the cable to his fish tape to push the cable up against the ice and let it do its thing -- then keep pushing it down range to maintain contact between the cable and the ice. Seven to tens days??
Any other ideas?
(*) - this problem shouldn't come as a surprise to me; due to the lay of the land between the bathroom and my septic tank, the drain pipe is only under 4-6" of dirt at one point (Colorado frost line in 30"). The edge of the blockage is at about the half way point.