Heat pipes spanning the 300°C to 500°C temperature range are still under research and development stage. Monel/water heat pipes have been previously explored as an option for operation up to 300°C. Life tests of up to 30000 hours have shown good compatibility at 250°C. The author explores the performance of a heat pipe using a different copper/nickel alloy with water as the working fluid at temperatures above 280°C. The performance of these water heat pipes at the upper limit of their operational temperature range in the horizontal position is highlighted and compared against numerical calculations of the heat pipe boiling limit. The use of these heat pipes in the context of thermal storage applications is also briefly explored.