Through-wall frost-free condensate drain
I am planning a heated utility building in a cold climate with no water, and consequently no drains. Nevertheless the building needs to deal with condensate from the HRU and the condensing tankless water heater used for in-slab heating. A proposed DIY solution for a through-wall frost free condensate drain is diagrammed here:
It seems to me that two features are highly desirable. The first is an auto siphon (the assembly inside the 4″ pipe) that will drain the water in pulses of 1 quart or so rather than in small trickles. The Worchester Bosch CondenseSure product is commercially available the UK for this application:
I did not investigate how practical it would be to purchase and install this product into a project in North America.
The second feature is a robust version of the technique frost-free hose bibs use to drain water from the pipe from a point inside the building envelope to the point of discharge into the open air. I propose running two parallel, vertically offset pipes at a 45 degree downslope through the insulated wall, terminating several inches from the wall and two feet or so above ground level. I expect this will minimize residual water in the lower drain tube when water is not flowing, and the upper vent tube should maintain the wall’s air seal. I propose using open channels to further direct the water away from the wall; those will likely become large icebergs over the course of the winter.
I still have the option to run a drain pipe down through the foundation, but I didn’t see any good termination choices for that. On my site I could run the drain to daylight, but the termination is going to get covered in snow for sure, so I expect it to plug with ice. I could run the drain to my foundation drain, which would hold quite a bit of volume before backing up when it also plugs with ice where it drains to daylight, but sealing the system to radon then becomes an issue.
The simple option is to drain to a large water tote and manually dump that outside when it gets full.
GBA Detail Library
A collection of one thousand construction details organized by climate and house part