A low-loss cryogenic fluid supply system 100 comprising: at least one main cryogenic fluid tank 50, the main tank having a gas outlet 51, a liquid outlet 61, a pressure build circuit 57, and a vent 59, the vent being configured to exhaust pressure from the main tank at a first pressure P1, the pressure build circuit being configured to build pressure in the main tank if the pressure in the main tank Pm drops below a second pressure P2 less than the first pressure P1; a backup cryogenic fluid tank 20, the backup tank having a gas outlet 21, a liquid outlet 31, a pressure build circuit 27, and a vent 29, the vent being configured to exhaust pressure from the backup tank at the first pressure P1, the pressure build circuit being configured to build pressure in the backup tank if the pressure in the backup tank Pb drops below the second pressure P2; a gas supply line 55 connected to the main tank gas outlet 51 and having a pressure regulator 54 configured to supply gas to a junction 70 at a third pressure P3 greater than or equal to the second pressure P2 and less than the first pressure P1; a main liquid supply line 65 having a heat exchanger 62 to vaporize liquid from the main tank liquid outlet 61 and a pressure regulator 64 configured to supply the vaporized liquid to the junction 70 at a fourth pressure P4 less than the third pressure P3; a backup liquid supply line 35 having a heat exchanger 32 to vaporize liquid from the backup tank liquid outlet 31 and a pressure regulator 34 configured to supply the vaporized liquid to the junction 70 at a fifth pressure P5 less than the fourth pressure P4; a backup tank backpressure regulator 24 configured to enable gas flow from the backup tank gas outlet 21 to a point 26 in the gas supply line 56 upstream of the gas supply line pressure regulator at a sixth pressure P6 greater than the third pressure P3 and less than the first pressure P1; and an outlet supply line 75 configured to flow gas from the junction 70 and having a point-of-use pressure regulator 74 configured to supply gas at an end use pressure Pu less than the fifth pressure P5. at least one main cryogenic fluid tank 50, the main tank having a gas outlet 51, a liquid outlet 61, a pressure build circuit 57, and a vent 59, the vent being configured to exhaust pressure from the main tank at a first pressure P1, the pressure build circuit being configured to build pressure in the main tank if the pressure in the main tank Pm drops below a second pressure P2 less than the first pressure P1; a backup cryogenic fluid tank 20, the backup tank having a gas outlet 21, a liquid outlet 31, a pressure build circuit 27, and a vent 29, the vent being configured to exhaust pressure from the backup tank at the first pressure P1, the pressure build circuit being configured to build pressure in the backup tank if the pressure in the backup tank Pb drops below the second pressure P2; a gas supply line 55 connected to the main tank gas outlet 51 and having a pressure regulator 54 configured to supply gas to a junction 70 at a third pressure P3 greater than or equal to the second pressure P2 and less than the first pressure P1; a main liquid supply line 65 having a heat exchanger 62 to vaporize liquid from the main tank liquid outlet 61 and a pressure regulator 64 configured to supply the vaporized liquid to the junction 70 at a fourth pressure P4 less than the third pressure P3; a backup liquid supply line 35 having a heat exchanger 32 to vaporize liquid from the backup tank liquid outlet 31 and a pressure regulator 34 configured to supply the vaporized liquid to the junction 70 at a fifth pressure P5 less than the fourth pressure P4; a backup tank backpressure regulator 24 configured to enable gas flow from the backup tank gas outlet 21 to a point 26 in the gas supply line 56 upstream of the gas supply line pressure regulator at a sixth pressure P6 greater than the third pressure P3 and less than the first pressure P1; and an outlet supply line 75 configured to flow gas from the junction 70 and having a point-of-use pressure regulator 74 configured to supply gas at an end use pressure Pu less than the fifth pressure P5.