Abstract: A mechanical seal for use in sealing the hole formed in a stationary bulkhead through which a marginal length of a rotating shaft is received. The seal includes a barrel attached to a flange so that the flange can be attached to the bulkhead with the barrel being concentrically arranged about the shaft and forming an annular passageway between the barrel and the shaft. A first and second flow restrictor, together with a seal means, form first and second spaced, annular chambers. The first flow restrictor separates the first annular chamber from a high pressure fluid. The seal means separates the first annular chamber from the second annular chamber. The second flow restrictor separates the second annular chamber from a low pressure fluid. The first flow restrictor retards flow from the high pressure fluid into the first annular chamber and vice versa. The seal means permits flow from the second annular chamber into the first annular chamber but prevents flow in the opposite direction.