Monday, July 6, 2009


Our crops that are planted at nominal ground level seem to be doing alright without watering. Now in early July without much of any rain in the month of June, the soil is moist down about 2 inches and the water table is down at about 2 feet.

It's a different story for those plants we set on top of raised beds. In the early spring we had thought it wold be necessary to put most of our planting on raised beds or mounds to get the roots up out of the water table. It is very low here on Ebey Island. How wrong we were. We didn't know that the water table would drop as far as it has. So we have had to carry in water and we have not been able to carry enough to feed our thirsty vegetables.

Some of us have dug shallow wells for water, and the deeper of those are working OK. However after we've drawn a few buckets from them, they run dry and it takes a while for them to refill.

So here's my idea: Mount a plastic rain barrel on a short tower -- say 4 to 6 feet off the ground. Fill it with water and connect a soaker hose to it. Lay the soaker hose along the tops of the raised beds and let gravity bring the water to the plants a drip at a time.

But how to fill the rain barrel. Obviously not rain. Then I thought about my boat. It has a 12volt bilge pump with a switch that operates it when the level of water in the bilge gets too high. (All boats that have engines inside the hull leak a little around where the propeller shaft(s) exit the hull.)

I could mount a bilge pump and switch on a board and sink the board into the well, the pump can raise the water 10 ft or more easily to fill the barrel. I could put another float switch in the barrel to prevent the pump from running when the barrel is full. Voila!

Oops, where could I get 12 volts DC to power the system? I could use a 12-volt battery and a solar or wind charger. A 360 gph (gallons per hour) pump draws 2.1 amps. So filling a 50-gallon rain barrel would take about 8 minutes. That would take almost 16 amp-hours of power from my battery or about 20 percent of an 80 amp-hour battery. Not too bad.

Let's say that when the system stabilizes it pumps with a 10 percent duty cycle so it would draw .2 amps/hour. That 80 am-hour battery would last 410 hours (17 days). I suppose I wouldn't mind taking it home to be re-charged every 2 weeks. Or I could bring my small generator to the garden to re-charge it.

But I have a better idea. I'm looking for a small solar charger so that my watering system can virtually forever. The sunnier (and hence dryer) the weather, the better it will work.

Stay tuned to hear more about how this works.


  1. I'm also researching the possibility of a pedal-driven all mechanical system.

  2. I did a test. I filled a rain barrel 3/4 full and attached a rubber soaker hose. The hose filled and beads of water appeared on the hose, but there wasn't any real flow. Then I lowered the soaker hose about 3 ft. Nice flow. This is an older hose and probably has some accumulation of gunk inside that impedes flow. With enough pressure, it flows. So my conclusion is that for gravity flow to a soaker hose, the rain barrel should be at least 3-4 feet higher than the area I'm trying to water.

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