Yews are very drought tolerant and rather shallow rooted so I'd probably go that route for evergreen.

Everything I've ever read says that anything woody (shrubs and trees) shouldn't be planted on a leach field. Though it may not be true for all shrubs, since some are shallow rooted, I've never felt any desire to test it out as a leach field is too expensive for me to want to mess around with it.

Sometimes a deciduous shrub will do as good a job as an evergreen in screening out unwanted views.

But - I'm with nhbabs, and you should get professional advice on what is and is not allowed over a leach field. I've googled this in the past, but it may depend on the type of system you have.

If the pipe is away from the actual field, that's another story.

I've done a lot of reading on this and spoken with the contractor. He said that "shallow root" plants should be fine with the system we have. Our actual field is on the deeper side allowed.

What kind of deciduous would you recommend though? I was thinking evergreen because I want something pretty to look at not just to hide the vent pipe.
Thanks
Chris

storey,
I think a very interesting point that troubles many people has been raised here. When trying to hide something from view the immediate assumption is that an evergreen is the best and only choice for year round screening. As an example lets compare the Spirea that you like with for argument sake the shallow rooting Rhododendron. The spirea is a densely branched fast growing deciduous shrub that will certainly screen your pipe, great fall color, and in the winter the bare branches will blend into the surrounding landscape. The Rhododendron while an attractive broad leaf shrub will take many years to settle in and begin to mature into an attractive shrub. In terms of screening keep in mind that this is not a densely branched shrub and during cold temps the leaves curl leaving you with an sparse shrub that does little to screen. Most importantly broadleaved evergreens that are not native to your surrounding community stick out like a sore thumb in a rural setting. kt

Thanks kt,
I see your point. I hadn't realized that the spirea had nice fall color too. That would be a bonus in this area. When referring to evergreen, I meant more of a conifer type shrub but am certainly not married to it at all. I don't whant a Rhodie here. I do know that. If the rains stay away, I'll check out the nursery this weekend and see what I can find. Thanks so much for sharing your perspective. I'm very new to this and appreciate your help, everyone.