Thanks for responding. I seldom water the lawn (unlike CO and WY where I had to), but I will be putting some new beds in next year (I hope) and I don't want to lose new trees/shrubs from salt uptake when I'm getting them established. I can shut the system down for 15-20 minutes while I'm watering house plants so I don't have to worry about that. However, it would be a PITB to do that while running sprinklers (and trying to get kids in the tub...sort of defeats the purpose of a softener).

I think you're going about this the wrong way! The majority of tree roots are in the top foot or two of soil. They are there, as opposed to being much deeper, because they need oxygen. The oxygen is delivered to them when water drains down through the soil. This drainage pulls gases down to root level. The water also brings nutrients to the roots. So pipes driven more than about 1 foot into the ground are going to miss most of the roots. When water drains like normal, it wets the ground over the entire rootzone of your tree. When you drive a pipe down into the ground (depending on your soil type) you may be wetting only a small cone of soil down under the pipe. This is an inefficient use of your water. If you dig down into your soil, I think you'll find that it's already moist down at a deeper level. Making it wetter will only reduce oxygen levels and drive roots back up to the surface. Tree roots in moist areas frequently do grow higher in the soil and along the surface so that they can get the oxygen they need.

Starting with Problem 3. what does you soil need? What did a good, reliable soil test say about what that soils needs? Problem 4. Depending on the weather your lawn needs about 1 inch of water per week and it is best to water enough at any one time to get that water deep into the soil, 6 to 8 inches down. But then hot and windy weather can cause moisture evaporation which can mean your lawn needs to be watered more often. Problem 2. The grass will grow back, eventually. As a rule after about 6 weeks you could overseed although my experience is that the grass will be growing back on its own by then. Problem 1. The presence of clover, most likely White Dutch Clover, indicates a protenial Nitrogen problem. A good, reliable soil test will help here because there are several things you need to know about what is in your soil to intelligently determine what to feed that soil. What is the soil pH? What is the balance between Calcium and Magnesium? What is the level of organic matter in the soil? Organic matter opens up clay soils so both nutrients and water are more readily available to plants and in sand it helps hold both nutrients and water in the soil so plants can utilize them. Grasses need about 2 pounds of Nitrogen per 1,000 square feet per year to grow well. 1/2 of that can come from the grass clippings, so mulch mowing is one of the better things to do. How much more Nitrogen needs to be added only a good, reliable soil test can tell you. Too much Nitrogen is a waste of your money since the excess simply flows out and pollutes the ground water.

I just ran trenches and laid pipe over the last 2 weekends. I did about 6 inches deep so they are out of reach of any equipment (eg aerator). I plan on winterizing with an air compressor, so I am not terribly concerned about going below the freeze line. I am in Central VA, so things might be different where you are. one lesson I learned was using a lawn edger to cut the turf away where the pipes would go. This allowed me to pull up about 3-4 inches of soil when I removed the turf that I "edged." I just set it aside and finished them rest with a trench shovel, piling the turf on tarps for easy cleanup. I've got two zones done, and this weekend I plan on the third zone.