Failure on the part of persons, firms or corporations to discontinue the use of any and all cross-connections and to physically separate such cross-connections before the 15th day of April, 1924, will be sufficient cause for the discontinuance of the public water service to the premises on which the cross-connections exist; unless the quality of the water from the two supplies used has been approved by the state department of health.

Provided, that in the case of persons, firms or corporations having installed before April 15, 1924, cross-connections consisting of two gate valves with indicator posts, two check-valves of the factory mutual type with drip cocks and gauges for testing, all to be placed in a vault of water-tight construction accessible to ready inspection; the date of discontinuance of the same shall be extended until January 1, 1927; provided, further, that such cross-connections are subject to such inspections as the state department of health deems proper, the expense of such inspections to be borne by the person, firm, or corporation using such a cross-connection.