A high pressure liquid containment joint in an apparatus for injecting high pressure liquid into turf. A preferred high pressure liquid containment joint includes an O-ring (72). The high pressure liquid containment joint also includes a cylindrical plug (70). The plug (70) includes a first end and a second end, external threads (71) located between the first and second ends, a shoulder (73) for accepting the O-ring (72) wherein the shoulder (73) is located between the external threads (71) and the second end. The plug (70) also includes a hexhead (75) connected with the first end for accepting rotational force. The high pressure liquid containment joint also includes a high pressure liquid containment vessel for containing high pressure liquid wherein the vessel includes a threaded bore (74) wherein the bore (74) includes internal threads (172) for engaging the external threads (71) and two, smooth machined frusto-conical surfaces (174, 175) for contacting the O-ring. The O-ring (72) and the frusto-conical surfaces (174, 175) form a liquid impermeable barrier when the external threads (71) engage the internal threads (172) and the plug (70) and the O-ring (72) are rotated relative to the threaded bore (74) and wherein the barrier lies between the high pressure liquid and the external and internal threads (71, 172) whereby stresses on the internal threads (172) in the containment vessel are reduced resulting in a reduced chance of structural failure of the containment vessel.