Trench Pump Can Really Move Water

By Staff
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by Gas Engine Magazine Staff
Regardless of the name, whether you call it a trash pump, mud pump, sludge pump, diaphragm pump or trench pump, this engine can really move water!

This kind of pump is known by a host of names: trash pump, mud pump, sludge pump or diaphragm pump, and its own manufacturer called it a “trench pump” — but regardless of the name, this pump can really move water!

Made by CMC in the 1940s, this pump is a Model FD3 and was designed to move difficult materials such as mud, slurry, sewage and other viscous liquids. With a rubber diaphragm that does the pumping and rubber flappers that do the valving, the pump is capable of moving about 90 gallons per minute and lifting water as much as 20 feet. Its unique construction allows it to handle solids mixed with the liquid, and this pump is able to pass 1-5/8-inch solids. That makes it ideal for pumping out trenches, which always have a mix of water, mud and gravel.

H. B. Lichty founded the Waterloo Cement Machinery Corporation in Waterloo, Iowa, in 1909 with the purpose of making cement mixers. The product line soon expanded to include hoists, trench fillers, brick and block machines, and pumps, and the company name was changed in 1920 to Construction Machinery Company, abbreviated to CMC. By 1922 they had 125 employees and a large factory and foundry. The company had a number of innovative products and a faithful customer following until it was merged into a much larger organization, Roper Industries, in 1976.

We acquired this CMC pump in poor condition, as the “before” photos above show. It had been used roughly on a beef cattle farm, and then stored outdoors. We quickly determined that the engine, a Wisconsin AB, had a host of problems, and we decided to replace it. We found a rebuilt ABN unit for sale at Bob’s Small Engine Repair, Marion, Iowa, that fit perfectly and starts and runs nicely. The ABN develops 3.4 HP at 2400 RPM, and has a good governor, which is an asset with a cyclic load like this pump. Because the pump crank and diaphragm work relatively slowly, about 60 to 120 strokes per minute, the engine has a reduction gearbox, which then drives an additional sprocket and chain reduction system. This reduces the engine speed and increases torque in order to operate the large diaphragm.

We rebuilt the flapper valves contained in each pump port, sandblasted and painted the pump body, and built and installed new primer plugs. Luckily for us, the diaphragm was intact and only needed cleaning. After some additional detail work, the result is seen in the “after” photos. We started the engine and we could hear the pump huffing and puffing and feel suction and pressure at the ports, but without a suction hose we couldn’t actually pump water.

Because of the strong suction, an ordinary hose in this service would collapse. What is required is a true suction hose with a steel spiral built in to keep the hose open even when lifting water from a ditch. It took us quite a while, but we eventually located a suction hose we could afford. After adapting the fittings, we installed it on the pump, and were finally able to see our efforts pay off. The photo, above right, shows the pump in action, lifting water from our swamp.

These types of trench pumps are still used in industry and construction today, but to meet safety standards, they are always covered with protective shrouds. We prefer our vintage model, which has lots of visible motion. It may be a trash pump, but it looks like a winner to us!

Contact Mike Intlekofer and Kirk Unzelman at 4472 119th Ave. S.E., Bellevue, WA 98006 •

  • Updated on Jun 3, 2022
  • Originally Published on Apr 3, 2012
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