ancillary outdoors temperature sensing unit 50 and indoors water supply line electrically actuatable valve therein includes a a 115 vac step down transformer a1 a2 a3 a4 b a double pole double throw 24 vac relay having several electrical contacts b1 b8 d a terminal block strip d having several electrical contacts d1 d8 emanating from terminal block d electrical leads d1 d8 for a novel combination 9aa of electrically interconnected elements 50 51 52 are the following a from d1 to one terminal of valve 51 and also to a3 b2 and b3 b from d2 to a second terminal of valve 51 and also to b6 and b7 c from d3 to one terminal of outdoors temperatures sensing unit 50 and to c1 and a4 d from d4 to a second terminal of said outdoors temperature sensitive unit 50 and to c2 b6 and b7 e from d5 to b1 and serially therefrom sprinkler valves e g 21 23 f from d6 to b8 and to a sprinkler valve e g 23 g from d7 to b4 and to control box 30 contact 34 and h from d8 to b5 and to control box 30 contact 33 i from one side of a sprinkler valve 22 to a control box 30 contact 32 and j from one side of a sprinkler valve 21 to a control box 30 contact 31 numeral 53 in drawing fig2 refers to another apparently novel feature i e an all brass automatic drain 53 in the egress line 14 specifically this drain 53 will serve as a safety device when water in the egress side 14 of the backflow unit 15 begins to freeze.