The Riverscreen is an innovative floating screen that can pump and filter out debris from running water as shallow as 4 inches. Bob Wietharn, the company’s founder and the inventor of the Riverscreen, has also invented a floating pump screen that can handle pumps moving anywhere from 20 to 5,000 gallons per minute. This makes it useful for a broad variety of applications, from supplying single users with water to supplying entire irrigation districts.
In this interview, Mr. Wietharn speaks with the editor-in-chief of Irrigation Leader, Kris Polly, about his invention and its broad variety of current applications.
Kris Polly: Please tell us about your company’s history and how you got started.
Bob Wietharn: In 1996, we attempted pumping water from a local river into a center pivot. It was nearly impossible because of the problem of plugging nozzles. The debris was so terrible that we had problems keeping the pump primed. The following year, I tried to find a screen to help me with the issue, but I couldn’t find anything available on the market. So in 1997, we built the first prototype Riverscreen and went through the summer with high hopes and even better results. The unit was originally made out of steel and was very heavy. Seeing that the prototype unit wouldn’t hold up over time, the following summer I set out to build one out of aluminum.
Word spread quickly, and soon my neighbors started asking me to build them Riverscreens as well. After building a couple the first year, word got around even faster. We built 12 Riverscreens with the expectation that we would have them in stock to sell over a couple seasons. That was 1999. By the fall, we had sold every unit we had built. This continued year after year, and we scaled our operations to try to keep up with demand. In 2001, we decided to incorporate. This was when Riverscreen became trademarked.
Kris Polly: What year did you make your first floating pump screen?
Bob Wietharn: In 2008, a drip tape company contacted me to ask whether we could put 120 mesh on our Riverscreens so that they could pump water out of rivers and streams directly through their drip tape. We proceeded to develop what we call a Gravity Flow Riverscreen. The outlet pipe of the Gravity Flow Riverscreen is submerged, and the rotating drum is about 70 percent submerged. This varies from our standard model, which is about 30 percent submerged and can pump out of as little as 4 inches of water. The point of this model is to get more of the rotating drum in the water, because in the past, we couldn’t get enough water through our standard Riverscreens when operating in extremely dirty water sources with a lot of silt. In the field test, the Riverscreen ran for about 2 hours. They said that 15 engineers had worked on this problem for several years and had never been able to pump from this particular stream without the screen failing after a few minutes.
Down the road, that company decided that our floating screens were too expensive for their market, so we ended up parting ways. I felt, though, there were other uses for the Gravity Flow Riverscreen, so we continued to develop it, and the version we offer now has been a tremendous success. Its popularity has grown even more since it started being used with our floating pump screens. Our floating pump screens, which have been on the market for 7–8 years now, use a standard centrifugal pump mounted vertically and floating on the same framework as the Gravity Flow Riverscreen. Set up like this, the volute can be submerged as well, and once the volute is half underwater, the pump becomes self-priming. It is a great option for anybody with an electric-driven centrifugal pump who needs to pull water from rivers, lakes, streams or livestock lagoons.
The Gravity Flow does require a deeper water source than our standard Riverscreen does. The smaller version requires water of a depth of about 16 inches, and the larger versions could need as much as 30 inches. Because of the water depth requirement, they tend to be most popular with customers who are pumping out of lakes, reservoirs, or livestock lagoons. We have sent many of them to California for use in irrigation. They use them in their small, canal-fed reservoirs.
We have started offering mesh sizes that are finer than our factory 8 mesh, for instance 120 mesh, which allows users to pump directly into drip tape. Another advantage of our floating pump models is the amount of screen area that is in the water. This keeps the intake velocity below National Marine Fisheries Service standards and, with the right mesh size, meets the agency’s other criteria. As a consequence, states with very strict environmental laws, like Maryland and Washington, prefer producers to use Riverscreens over other available options.
Kris Polly: What kind of pumps do you use with the floating pump screen, and how much water can they pump?
Bob Wietharn: We are a Cornell dealer and supply their pumps for the unit, but other manufacturers’ pumps will work with our system as well, if they are close coupled. We have a series of adjustment holes that allow us to use different-sized pumps on our three available sizes. The size of the floats depends on the size of the pump and motor. We offer 4-inch, 8-inch, and 12-inch outlets on the Riverscreen. The discharge size of the pump can be customized to fit into an existing system. Our Gravity Flow model can handle anything from a pump that moves 20 or 30 gallons per minute up to a 150-horsepower pump that moves 5,000 gallons per minute.
Kris Polly: How many countries do you have your products in now?
Bob Wietharn: We have sold our floating pump in three or four countries. As far as Riverscreens in general, I would say we sell in over 50 countries now. We’ve lost track. We just recently sold two screens in Greece and Germany. This is the first time we’ve sold in Greece.
We have a unit in Papua New Guinea in an area where the only water available is unfiltered surface water. We put 320 mesh on our Gravity Flow Riverscreen and sent it over there on a floating pump. It only pumps about 50 gallons per minute, but that is extremely dirty water going through 320 mesh, which is so fine that the holes in it are roughly half the width of a human hair. The water is then used as potable water for the town.
Kris Polly: What’s the largest floating pump you’ve done?
Bob Wietharn: I believe we have done a 200-horsepower open drip proof electric pump. That was more of a high-head pump. It all depends on the weight of the motor. Totally enclosed fan cooled motors are much heavier than open drip proof motors. Another good example are the three large pumps we provided an irrigation project in North Dakota that pumps out of the Missouri River. Those are 150-horsepower pumps that move 2,700 gallons per minute. All those pumps are automated and on variable-frequency drive. When one partner wants water and opens the valve, the pressure drops and the pumps come on. The more farmers open valves to supply their pivots, the faster the pumps speed up.
Kris Polly: Is there any final message that everyone should know about your pumps and your screens?
Bob Wietharn: The huge advantage is that it’s self-priming. Because the volute is over 50 percent submerged, all you need to do is start the motor and it will instantly be primed. They also have a skid framework under them for easier installation or removal. We also clean the screen in the atmosphere, as with our standard Riverscreen; it takes very little water and very little pressure.