CSV versus VFD
The way pumps are built these days, not much that can be recycled. Plastic or "composite" impellers, internal electronic circuit boards, and encapsulated windings make it practically impossible, and certainly non-profitable to recycle. Manufacturers have turned it into a "throw away" society. Products are to be trendy, expensive, short lived, and non-repairable. Electronic products can be made of materials that are mined and smuggled out of the Congo with slave or child labor. They can be manufactured in third world countries with no heath or environmental concerns. Their use can cause "stray voltage" or "harmonics" that can be devastating to animal or human health, as well as the electrical grid. Profits go to non-American corporations, and even countries with dictators and despots in control. Then after their short life, products end up filling our landfills and leaching heavy metals into our water supply. If they can deceptively convince the public that it will save energy, then they can still call it "green". However, the only thing "green" about it, is what is coming out of your pocket to make all this happen.
Products that are made to last a long time can even use more energy, and still be more "green" than products designed for "planned obsolescence". Not that well built products will use more energy but they could, and still be better for the environment.
The worst thing you can do is fall for the products that big corporations are spending the most money advertising. They don't push products to help save you money or save the environment. No mater what they actually say, they spend the most money advertising products that make them the most money. Whatever makes big corporations the most money, cost you the most, and is usually the worst thing for the environment.
Pump system "specs" should not only be concerned with gallons per minute, pressure required, and energy savings, but should also require long lasting products that can be recycled, which causes the least damage to the environment and your pocket book.
While VFD's are short lived and almost impossible to recycle, a CSV will last a long time and is 100% recyclable. While the pumps and motors these devices control are not conducive to recycling, the CSV makes pumps last longer, and therefore drastically reduces landfill waste compared to VFD controls.
Many Americans are now bringing their own cloth bags to the grocery store to reduce landfill waste. It is even more important that what we purchase is long lasting and completely recyclable.
Cycle Stop Valve verses Constant Pressure Pump video
CSV verses VFD demo
PBS Review Video
VFD to CSV Changeover