The facility design problem for the multi-floor plant is observed for improvement on the Water Filter Production Building Layout. This study was to propose improving plant layout with the CORELAP method and achieve line balancing with the Ranked Positional Weights (RPW) method and ECRS (Eliminate, Combine, Rearrange, Simplify) principle. Daily production of water filter model D got a long total traveling distance of work-in-process. Furthermore, employees of each group got unbalanced workload assignments, with bottleneck consequences. Hence, the production line had to be improved concerning layout and line balancing. There were three new proposed layouts according to the Computerized Relationship Layout Planning (CORELAP) principle. The findings showed that Layout 3 had the shortest total distance, lowering the previous by 649.43 m, determined as the optimal layout. Line balancing against six work groups, each workgroup had a different capacity owing to the limited workers. Hence, the improvement used average production for calculation. Workgroups 2 and 6, having the highest increase in the amount of output, were considered for line balancing. As a result, Workgroup 2 produced 440 units per day, which increased by 302 units per day, and Workgroup 6 delivered 362 units per day, which increased to 94 units per day. Event simulation by the Arena program revealed the practicality of production by workgroups 2 and 6 were just 437 and 354 units per day.