Section R. 325.1657 - Pump installation; ventsRule 157.
(1) A casing vent shall be provided on all well caps and seals, except for those used on deep well, single pipe-packer jet installations, or on flowing wells where the flow rate is greater than the pumping rate of the permanent pump. A vent shall be screened, pointed downward, and terminate not less than 12 inches above the ground surface or above the floor of an approved basement, basement offset, or pump room, and at a point not less than 24 inches above any known flood level. Vents may be offset if they are in compliance with the provisions of this rule. Vents shall be in compliance with the minimum sizes listed in table 4. Table 4
Minimum Well Casing Vent Sizes
Casing Inside Diameter (Inches) | Circular Vent Diameter (Inches) |
| 2 | ¼ |
| 4 | ½ |
| 5 or 6 | 3/4 |
| 8 or larger | 1 |
(2) Vent screening shall be not less than 20-mesh per inch and not more than 30-mesh per inch screen. Screening shall not reduce the vent open area by more than 50%.Mich. Admin. Code R. 325.1657