Sounds like you are depleting your water before it can get to the end. Perhaps your system is using more water than what you have to give it? Can you split it up, into 2 sections?

clysta,

2lips is correct. If your system was splitting before it probably has too high pressure and needed pressure regulation to around 20-25 psi for drip. If it has suddenly changed to what you are experiencing, you have too little pressure at the end. Possibly a leak between the beginning and end of the tube robbing your line toward the end of pressure. The leak should be very visible from the drip line. Check your water source pressure and post it here for further analysis. JMHO Aloha

I guess I should have explained that my system was installed by the builder. The two main lines are about a foot underground. The two leaks that I had were noticible because there was a pool of water on the surface. I see nothing like that now.
I have two main lines, one feeds the bushes and the other feeds the trees. And, of course, I have many more shrubs than trees. I will plug more of the bush drippers and see what happens. Hand watering in the meantime.

If I remember correctly, a simple moisture meter with about 7 inches of probe on it can be purchased for around $15. Stick it in the ground along the length of the main lines. If it spikes somewhere, then you have a leak in that area. Call the builder and read him the riot act - replace all that underground piping. This would be your 3rd leak. You can use the meter to see if trees and shrubs are getting enough water and you can also use it in the garden for the same reason. The purchase is not unreasonable.If you tapped off somewhere in your house water supply, then every time someone gets a glass of water or flushes, the pressure to the Trees and Shrubs will drop, maybe even quit. If your builder "T"d on the main water line into your home, then, this won't happen. At the "T" the lines that feed trees and shrubs should be 1 inch into the area watered, then it should be 3/4 inch piping to the drip units. The amount of drip heads you can use on each line is determined by the unit itself and a mathematical formula that considers the water pressure at that point and the circumference of the pipes. You can figure all this out yourself. Go to Lowes or any store that carries lot's of permanent home sprinkling stuff and they'll have a flyer that will tell you how to do all this. Home Depot is another place to go to. Each major sprinkler manufacture has these flyers and you can probably get the feller at the store to figure it out or contact the company online and they'll do it.

Yes, I have a water meter and usually monitor the water system. I hadn't though about using it to test for a leak. If I can stand the heat I will do some testing tomorrow. What has me concerned is that the system worked fine when I bought the house new in 2006. Now several things are not working well.