Section 58.01.08.536 - DESIGN STANDARDS FOR FLUORIDATION01.Chemical Feed Equipment and Methods. In addition to the requirements in Section 531, fluoride feed equipment must meet the following requirements: a. Scales, loss-of-weight recorders or liquid level indicators, as appropriate, accurate to within five (5) percent of the average daily change in reading will be provided for chemical feeds.b. The accuracy of chemical feeders used for fluoridation will be plus or minus five (5) percent of the intended dose.c. Unsealed storage units for fluorosilicic acid will be vented to the atmosphere at a point outside any building.d. Fluoride compound may not be added before lime-soda softening or ion exchange softening.e. The point of application of fluorosilicic acid, if into a horizontal pipe, will be in the lower half of the pipe.f. A fluoride solution will be applied by a positive displacement pump having a stroke rate not less than twenty (20) strokes per minute, and at a feed rate not less than twenty (20) percent of the rated capacity of the feed pump.g. A spring opposed diaphragm type anti-siphon device will be provided for all fluoride feed lines and dilution water lines.h. Except for constant flow systems, a device to measure the flow of water to be treated is required.i. The dilution water pipe will terminate at least two (2) pipe diameters above the solution tank.j. Water used for sodium fluoride dissolution will be softened if hardness exceeds seventy-five (75) mg/1 as calcium carbonate.k. Fluoride solutions will be injected at a point of continuous positive pressure or a suitable air gap provided.l. The electrical outlet used for the fluoride feed pump will be interconnected with the well or service pump.m. Consideration will be given to providing a separate room for fluorosilicic acid storage and feed.02.Secondary Controls. Secondary control systems for fluoride chemical feed devices must be provided as a means of reducing the possibility for overfeed; these may include flow or pressure switches or other devices.03.Dust Control. Provision must be made for the transfer of dry fluoride compounds from shipping containers to storage bins or hoppers in such a way as to minimize the quantity of fluoride dust which may enter the room in which the equipment is installed. The enclosure must be provided with an exhaust fan and dust filter which places the hopper under a negative pressure. Air exhausted from fluoride handling equipment must discharge through a dust filter to the outside atmosphere of the building.Idaho Admin. Code r. 58.01.08.536