Abstract: A hydrostatic pipe testing tool for use in oil field in cooperation with the bar string has upper and lower mandrel tools substantially identical and comprising a cylindrical collar threadably connected to a cylindrical piston and coaxially alligned with it so the central bores of the collar and the piston fluidly communicate with each other. A shaft integrally attached to the piston has a sleeve slidably mounted thereon. Two resilient sealing elements are spaced by three steel spacer rings and mounted circumferentially and slidably on the sleeve. Another sleeve is provided for attaching the shaft and the first sleeve to a bar string. The filling port of enlarged diameter is made perpendicularly in relation to the central bore in the piston portion of the mandrel and a filling jet is disposed at 45.degree. angle in relation to the central bore. A plurality of O-rings define fluidly sealed chambers for facilitating testing of the tubing within a well bore.