Saturday, February 21, 2009

SPURT stream drip (drip drip drip part 2)

So today we started connecting bits of our drip system, and we got a rude awakening. We ran a 1/2" mainline down the length of the garden, and in the first bed we ran 2 12' lengths of 1/4" tubing, with holes spaced a foot apart. Well. When we turned on the water, what appeared before us was an exponentially decreasing water pattern. The first hole spurted water several feet in the air, while the last hole was completely dry.

We did a variety of experiments to attempt to remedy this, and none of them worked. It seems as though we should have bought the much more expensive pressure compensating tubing, which maintains even water pressure at each emitter. Is this the only solution? Is this a situation where our DIY determination and cunning cannot save us?

Help, please!


Mikey Sklar said...

Ahh, the scam of store bought irrigation systems.

I got totally frustrated looking at the price of irrigation hose and all the silly adapters and emitters required. We built our system out of 3/4" PVC. Although rigid the cost is surprisingly affordable and very easy to attached adapters. We just drill 1/8" holes in the tubing and the water makes it to the end.

You can use simple PVC valves for turning the water on or if Tristan is interested in doing some automation it is no big deal to rig up a $18 solenoid to water the yard based on time of day / duration or use a ADC for measuring soil conductivity. I have a few extra irrigation boards if you guys go this route.

The Fuz said...

So it looks like you're probably using too large (or too many) of holes in the system. If I'm remembering my high school physics correctly, the total amount of cross-sectional area of the outlet holes must be less than or equal to the area of the inlet pipe in order to have the pressure be equal in the system. Once you've accomplished that, it's a matter of compensating for the pressure in the system (usually with a valve between the spigot and inlet tubing) in order to get your "drip". Hope this helps.