Wirtz pumps have been around for a few hundred years, but haven’t been used much since steam powered pumps came along. Click here for a great resource about Wirtz pumps and the science behind them, as well as further details about the pump that was built at the Windfarm Museum in New Hampshire. Their pump uses “6 foot diameter wheel with 160 feet of 1-1/4 inch inside diameter flexible polyethylene pipe is able to pump 3,900 gallons of water per day to a 40 foot head with a peripheral speed of 3 feet per second.”
They also ran experiments that confirm that these pumps work quite well regardless of how quickly the water source (stream/irrigation ditch) is moving. The amount of water pumped increases pretty linearly with the water speed, but even at very slow speed the pump still operates at about the same overall efficiency.
Materials used in the Pangea Farm version (total cost = ~$250)
For the paddle wheel:
– Heavy cable spool (from local utility company junk pile) for the wheel;
– Cedar 1″ thick boards for paddles;
– Paddle wheel axle, either very heavy gauge tube, or 2″ solid stock, machined at end to accept inlet of the main coil;
– Pillow block bearings to hold the axle (worth the extra cost for their durability and ability to absorb lateral force if axle is out of square with mounts).
For the scoop and coil:
– 4″ pvc scoop with wire mesh screen and reducer fittings, to scoop water into the main coil;
– Check valve between scoop and main coil, so water doesn’t flow backwards;
– Compressed air port at scoop end of coil (for blowing water out coil for winter storage);
– 100′ of 1″ poly hose, coiled on paddle wheel
– Waterproof swivel joint, joining rotating axle to the stationary pipe carrying water to holding tank.
For the storage tank and outlets:
– Reclaimed telephone poles to hold the tank up high;
– Water tank (500 gal, fills in ~8 hours);
– 1″ water line and filter from tank to irrigation system;
– Overflow line to return water to ditch when tank is full.
Lots of possibility for modification for other uses!
Project is for: Vegetable and fruit growers who need to filter irrigation water
Range of cost: $325 – $450
Skills / tools needed: Pipe wrenches, ability to glue PVC fittings together
Summary: When using drip irrigation, it’s important to have a good water filter system, especially if you are using surface water (from a pond or stream). At Hearty Roots Farm, we pump from irrigation ponds that have silt, algae, pond weeds and other particles that would clog up our drip lines if they didn’t get filtered out.
When our farm was smaller, we just used a simple disc filter and once in a while we would take it apart and clean the filter element with a hose, since it would get clogged up with algae and dirt which reduces the flow rate and water pressure. However, as our irrigation systems grew, we needed a more efficient way to filter our water without breaking the bank. Sand filters work well but they are not easily portable and they cost upwards of $1,000. We built our own easy-to-back-flush filter using two disc filters and some pvc pipe fittings, for just over $400. Now we can clean out our filter in a matter of seconds, while the system is still running, and therefore we have very little water pressure and volume loss due to clogged filters.
* Note that Amaid also makes a “Scan Away” disc filter, for about $410, which achieves similar results to this. I haven’t used it, so I can’t vouch for it. I built this version because I already had a regular disc filter– I bought mine before the Scan Away model existed– so this approach was more economical for me, and now I have two usable filters. Plus, there are fewer moving parts to break.