A diverter/mixing valve comprising: a main outer housing having a first inlet port, a second inlet port, an outlet port, and an inner support having a frustoconical shape, a first end connected to the first inlet port of the main housing that forms a channel disposed around an inner perimeter of the first end of the main housing, a second end distally located from the first end, a side surface that extends circumferentially from the first end to the second end, and inlet openings defined in opposite sides of the side surface; a barrel assembly rotatably disposed inside the main housing, the barrel assembly including an inner sleeve having inner flow openings defined therein and an outer sleeve having outer flow openings defined therein, the inner sleeve having a conical shape and includes a first end slidably disposed in the channel, a second end distally located from the first end, a side surface circumferentially extending from the first end to the second end, and inner flow openings defined in opposite sides of the side surface, the inner sleeve mating with the inner support of the main housing when the barrel assembly is inserted into the main housing; and an actuation device rotatably connected to the inner sleeve of the barrel assembly, the actuation device rotating the barrel assembly between an open end inlet position where a first fluid stream flows into the first inlet port, through the inner sleeve, and out the outlet port and a second fluid stream is blocked from flowing into the second inlet port, and an open side inlet position where the second fluid stream flows into the second inlet port, through the outer sleeve, and out the outlet port and the first fluid stream is blocked from flowing into the first inlet port. a main outer housing having a first inlet port, a second inlet port, an outlet port, and an inner support having a frustoconical shape, a first end connected to the first inlet port of the main housing that forms a channel disposed around an inner perimeter of the first end of the main housing, a second end distally located from the first end, a side surface that extends circumferentially from the first end to the second end, and inlet openings defined in opposite sides of the side surface; a barrel assembly rotatably disposed inside the main housing, the barrel assembly including an inner sleeve having inner flow openings defined therein and an outer sleeve having outer flow openings defined therein, the inner sleeve having a conical shape and includes a first end slidably disposed in the channel, a second end distally located from the first end, a side surface circumferentially extending from the first end to the second end, and inner flow openings defined in opposite sides of the side surface, the inner sleeve mating with the inner support of the main housing when the barrel assembly is inserted into the main housing; and an actuation device rotatably connected to the inner sleeve of the barrel assembly, the actuation device rotating the barrel assembly between an open end inlet position where a first fluid stream flows into the first inlet port, through the inner sleeve, and out the outlet port and a second fluid stream is blocked from flowing into the second inlet port, and an open side inlet position where the second fluid stream flows into the second inlet port, through the outer sleeve, and out the outlet port and the first fluid stream is blocked from flowing into the first inlet port.