We have an existing hydronic radiant heat system under the floor between joists in the crawl space, coming from hot water heater (through a temperature reduction mixer thing) to the kitchen. Works great. We would like to add to the system to go to the bathroom. Can we simply "splice the existing tubing" and run it to bathroom before returning to the hot water heater? or do we need to run a separate zone? What is the best way to add on? Do we need another whole system? Crawl space is 7' tall so no issue with working under there. We want to DIY because the quote we received from the plumber to add on, was equal to installing the original system. If splicing is okay, how do we work with the air that is in the line then? it just runs into the hot water tank and gets eliminated there? As you can tell, we're finding our way...