Iowa Admin. Code r. 875-92.9
This rule applies to power boilers installed prior to July 1,1983. Outlet connections that allow the escape of an appreciable amount of steam or water shall not be placed on the piping. However, this rule does not prohibit the installation of damper regulators, feed water regulators, low-water fuel cutouts, drains, or steam gages. The water column shall be provided with a drain of at least 3/4-inch piping size. The drain must have a valve and be piped to a safe location. Each boiler shall have three or more gage cocks located within the visible length of the water glass, except when the boiler has two water glasses located at the same horizontal lines. Only two gage cocks are required on boilers not over 36 inches in diameter with a heating surface not exceeding 100 square feet. Gage cocks are not required on electric boilers.
Iowa Admin. Code r. 875-92.9