Finally system refilled after underground pex redo and total redo of first season leaky boiler room fittings (wrong pipe sealant). Found a pinhole leak in the HX manifold. Do I have to drain the HX or get all water out to repair this? Should I get my heating contractor come and solder this? Have a small torch for starting boiler fires but have never soldered any copper fittings. Sure don't want to do more damage to this important joint. Thanks