As it "may" be temporary, I would certainly use sharkbite push on fittings like the one at the bottom of the blue pex line. Brass Push Cross Tee Reduces installation errors with an innovative push-to-connect design for joining two pipes of different sizes. www.sharkbite.com SharkBite Max...
Fitting 3 size 1/2" Fitting or Connector Type Tee Manufacturer Warranty 25 Years: For exclusive use with ASTM F1960 fittings, fasteners and pipe. Material Brass Pack Size 1 PEX Type A Pipe or Fitting Product Type Fittings & Connectors ...