Design concepts are addressed for low pressure float valves which are intended for hydroponic and sub-irrigated container gardening systems to automatically control water levels. Float valves are designed to work only at low pressures (maximum pressure is 4.3 psi) where water is supplied by gravity flow from a tank which is not more than 10 ft above the float valve. Clogging of the mechanism by roots is discouraged because the float body is nearly completely enclosed. Float valves may be made with readily available materials. Materials cost from $1 to $3 per float valve. This video describes how to build working models of 2 float valve designs and suggests that improvements are invited.
The nozzles, tubing and foam seal of both models plus the bottle of Model 101 and body of Model 102 are made of polyethylene and polypropylene plastics. Material Safety Data Sheets report that these plastics have low toxicity to humans and animals, but additives that leak from the plastics might have some harmful effects if inferior materials are used in the manufacturing process. PVC is used in the cap and body of Model 101. There are health concerns associated with some aspects of PVC plastics, but PVC pipe is rated and approved for drinking water and PVC pipe has been used in water systems for many years. Polystyrene is used for the float material in Model 102. Styrene has known health hazards, mostly by workers breathing fumes from workplace air. Styrene is very insoluble and escapes from water by volatilization. Polystyrene is used to manufacture commonly used beverage cups and one study did not detect styrene in cold water sitting in polystyrene cups, but styrene was detected in hot beverages above 122 degrees F. Irrigation water will be cooler and should pose a low risk due to the insolubility of styrene at low temperatures. Only about 0.25 grams Shurtape IT-100 is used per float valve. The product is composed of polyethylene foam with less than 1% (w/w) of an acrylic adhesive. The product does not contain chemicals known to CA to cause cancer or reproductive toxicity and contains no substances of very high concern (SVHC) above 0.1% (w/w). We should continually seek out safer materials as we try to improve the float valve design.
The technical assistance and encouragement by Ron Leatherman is gratefully appreciated and acknowledged. Ron is the son of a farmer and was active in the farming industry in his early life. He has written 2 books about experiences of living on a Texas farm “The Farmers Children” by Ron D. Leatherman (Amazon).
Post time: Jun-20-2017