Q&A About the Stefani float valve (BPA-free) and its remarkable non-toxic materials and manufacturing methods
The float valve we use in the Food Rising Grow Box 2.0 is available online as the "Stefani Plastic Float Valve for Gravity Water Filter." It is a marvel of engineering that's made almost entirely with non-toxic, chemically-resistant materials. (You can purchase one yourself for under $8 on Amazon.com.)
This float valve is almost entirely made from high impact polystyrene, a strong, chemically-resistant material that's exactly the same material we use in the Natural News Forensic Food Laboratory to hold liquids that resist strong acids such as nitric acid (HNO3) and hydrochloric acid (HCl).
We have conducted precise tests in the laboratory using ICP-MS instrumentation and have found that water leaches MORE metals out of a glass jar than any elements coming out of high impact polystyrene. (Yes, tap water will actually leach enough lead out of the glass of a glass jar to measure the lead atoms via ICP-MS.)
A very tiny part of the valve -- the soft valve closing ring -- is composed of low-density PVC. The miniscule size (6mm) of this part means any impact on your water quality and composition is negligable.
To achieve its remarkable non-toxic status, the three key parts of the valve are welded together using "ultrasonic welding" instead of toxic glues or resins. Ultrasonic welding vibrates the molecules of the pieces at high speed, briefly turning them into high-temperature liquids that bond together into a single structural piece once cooled. It's much the same way that metal is welded, but instead of using high amperature electricity (arc welding), this manufacturing process uses ultrasound.
Finally, this Stefani float valve was manufactured from the very start to sit in drinking water that has already been filtered by a gravity filter. For this reason, its materials and manufacturing process was carefully selected to be fully compatible with safe, ultra-filtered drinking water.