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Each time an irrigation valve turns on, I hear a noise in the house. When you're in the basement, the noise seems to be coming from the corner of the basement where the water line enters the basement and goes through the pressure regulator. The noise is not as loud as a water hammer, but can be heard in the main level of the house too (if the house is real quiet).

Of course noises in plumbing are not unusual. Even before we installed the irrigation, we always got some sort of odd noise when I would turn off the hose bibb that is also before the pressure regulator.

Here's the rest of the setup:

HOUSE:
I've got 1" PVC from the water meter at the street to the house. Somewhere just before the waterline enters the basement, it transitions to 3/4" copper. The distance from street to house is on the order of 50-75ft. Unregulated pressure is about 75psi and the house regulated pressure is 50psi.

IRRIGATION:
The Irrigation system Tees off the mainline just after the water meter. The system starts with a Y-Filter and Double Check Backflow Preventer. After a 10ft run, the irrigation Tees; one line is for valves on the far side of the driveway, the other runs a distance of about 15ft to valves on the near side of the driveway.

Both sets of valve boxes are setup in the following similar fashion. The mainline Tees with one line running to valves for high-pressure irrigation for the lawn, the other runs through a PVC pressure regulator and on to valves for drip irrigation.

The Y-Filter is Rainbird PVC rated for mainline, the DC is a 1" Watts 007, the pressure regulators in the valve boxes are Rainbird 30psi and 40psi. The valves are all 1" low-end Rainbird PVC valves. The entire irrigation system (both lawn and drip) uses check valves so that water stays in the pipes and doesn't sputter on startup.

Any thoughs on exactly what this noise is and why I can hear it in the house back through all this plumbing?

<i>It's a lot of time consuming work to trace plumbing noises and it depends upon the noise, but I can learn to live with some plumbing noises.</i>

This is definitely something that falls into that catagory. The noise is not particularly load nor annoying such that something has to be done about it. I'm just curious HOW this noise is happening. It's not like I hear my niebor's irrigation turn on in my plumbing (granted you got a pair of meters and the 6" mainline to make the jump).

It's just not a noise I was expecting given that:
1) the irrigation is all outside,
2) the valves are about 100 "pipe" feet from the house,
3) the noise has to travel back throught the double check backflow preventer,
4) all pipe is 1" PVC with flows on the order of 5gpm or less.