The Williams & Davis Series 4000W is a traditional 4-pass, water-back horizontal firetube boiler that offers high efficiency, flexibility, reliability, safety and ease of operation. Series 4000W provides high flue gas velocities and low stack temperatures to maximize its performance. All units are factory fire tested and shipped as an integrated package, ready for quick connection to utilities. Built to exceed ASME standards, the Series 4000W positions itself well above its class. This is a company principle that continues to make W&D a top choice in the industry.