LK 521 MultiFill® Brine Filling UnitLK 521 MultiFill Brine Filling Unit LK 521 MultiFill is a combination valve for easy filling of refrigerant fluid into ground source heat systems. The valve has a filter to protect the evaporator against possible grit. Its compact construction allows it to be installed in tight spaces. The valve comes with insulation to protect against condensation and possible icing. LK 521 MultiFill can also be used in other applications where filling and filtration