Well maybe the water is fine there. On your spot. It's possible there's a nice spring fed vein of water there. You may have to check it out. ...or just be okay with the fixtures with their added metals, like Ralphie said. Or keep a small little furnace in the mechanical room plugged in...shut the door. Voila.
We actually do this here at work for an out building that needs to keep running water for horses. Pump room is enclosed, insulated and small electric furnace near the pump and water lines. Works like a charm. There is somebody up there every day though...making sure it's running. But it has not failed, in the years we've been doing this.
https://www.amazon.com/PELONIS-NY15...3-spons&keywords=small+electric+heaters&psc=1
It's something along these lines. hey this one has a thermostat. So will shut off if it's an nice spring...until you get up here...sort of thing.