A tube fitting comprising: a first coupling member having an internal passage extending along a longitudinal axis and having: at least a snap coupling; a seal portion having a first seal surface formed in a wall of the internal passage, the first seal surface being a conical surface, having a conical angle (θ), and a second seal surface at an end face of the seal portion; a second coupling member having: a first quick-connect side having a mating snap coupling disposed at a first end of the second coupling member, and a second quick-connect side configured for threaded engagement disposed at a second end of the second coupling member, the second end being opposite the first end; wherein the mating snap coupling is configured to engage the snap coupling to effect coupling of the first and second coupling members; a third coupling member disposed between the first coupling member and the second coupling member, the third coupling member having: a seal portion forming a conical sealing surface, where a conical angle of the seal portion corresponds to the conical angle (θ) of the first seal surface for allowing sealing engagement between the first and third coupling members; and a flange extending radially from a peripheral surface of the third coupling member and including a flange sealing surface; a first elastomeric seal placed over or otherwise affixed to the conical sealing surface of the seal portion such that when the seal portion is inserted into the first coupling member the first elastomeric member engages both the first seal surface and the conical sealing surface to form a first fitting seal; and a second elastomeric seal placed against the flange sealing surface or at least partly within the flange such that when the first coupling member and third coupling member are engaged or otherwise fitted together the second elatomeric seal forms a seal between the flange sealing surface and the second seal surface to form a second fitting seal. at least a snap coupling; a seal portion having a first seal surface formed in a wall of the internal passage, the first seal surface being a conical surface, having a conical angle (θ), and a second seal surface at an end face of the seal portion; a second coupling member having: a first quick-connect side having a mating snap coupling disposed at a first end of the second coupling member, and a second quick-connect side configured for threaded engagement disposed at a second end of the second coupling member, the second end being opposite the first end; a first quick-connect side having a mating snap coupling disposed at a first end of the second coupling member, and a second quick-connect side configured for threaded engagement disposed at a second end of the second coupling member, the second end being opposite the first end; wherein the mating snap coupling is configured to engage the snap coupling to effect coupling of the first and second coupling members; a third coupling member disposed between the first coupling member and the second coupling member, the third coupling member having: a seal portion forming a conical sealing surface, where a conical angle of the seal portion corresponds to the conical angle (θ) of the first seal surface for allowing sealing engagement between the first and third coupling members; and a flange extending radially from a peripheral surface of the third coupling member and including a flange sealing surface; a seal portion forming a conical sealing surface, where a conical angle of the seal portion corresponds to the conical angle (θ) of the first seal surface for allowing sealing engagement between the first and third coupling members; and a flange extending radially from a peripheral surface of the third coupling member and including a flange sealing surface; a first elastomeric seal placed over or otherwise affixed to the conical sealing surface of the seal portion such that when the seal portion is inserted into the first coupling member the first elastomeric member engages both the first seal surface and the conical sealing surface to form a first fitting seal; and a second elastomeric seal placed against the flange sealing surface or at least partly within the flange such that when the first coupling member and third coupling member are engaged or otherwise fitted together the second elatomeric seal forms a seal between the flange sealing surface and the second seal surface to form a second fitting seal.