The influence of transpiring wall designs on supercritical water oxidation (SCWO) reactors is thoroughly studied. Design considerations such as materials, pore sizes, or designs of the wall are examined for different proposals of transpiring walls. Three designs were tested: a fully porous wall made of porous sintered AISI 316 and alloy 600 and two partially porous walls made of porous sintered alloy 600 and nonporous alloy 625. The nonporous material was used for areas especially affected by high temperatures or for areas where a transpiring flow is not needed. Operational results obtained working with the different proposals of transpiring wall reactors (TWRs) for the SCWO process are thoroughly examined and compared. Transpiring flow inlet temperature profiles are shown. Temperature and conversion profiles are calculated with a mathematical model developed for the reactor, resulting in similar behaviors of the reactor when working with different wall proposals. The influence of transpiring flow and its temperature on reactor behavior and on total organic carbon (TOC) removal is studied experimentally, showing a slight influence of the transpiring wall parameters on TOC removal. The influence of transpiring flow on temperature profiles is greatly minimized with the partially transpiring wall design. Wall fouling problems are described, and solutions such as periodical cleaning and recirculation of the effluent as transpiring flow are proposed to minimize the problems.