Question
Just over a year ago, we bought a house that has a six zone irrigation system controlled by a Weathermatic timer.  Zone 4 consistently begins its cycle with a sound similar to pipe hammering; however, it is coincident with the Watts 800M4FR Regulator popping with water pouring out of the top cap.  Zone 4 has three sprinkler heads all of which are about 3 feet higher than the regulator.  All automatic control values are below ground in a covered "box".  The system uses 3/4" pvc pipe, but the water source appears to have originally been a standard hose bib.   The contractor who opened the system last spring waved his hand and said, "Well, it's not a very good system."  Last summer was noisy.  Irrigating at 4:30AM meant Zone 4 was going to wake us.  What is the regulator doing and how can we quiet our system?   Thanks.

Answer
Hey Mike I hope this helps. The Watts regulator you are refering to is actually a vacuum breaker. A vacuum breaker is simply a device that allows the water to flow from the main water source to the irrigation system, but doesn't allow it to flow the opposite way. If it was allowed to flow from the irrigation system, back into your house, it could be contaminated water, and make you sick. This device "vacuum breaker" is required by city code. What your vacuum breaker is doing, is waiting for the pressure to build up in this particular valve, in the mean time, there is a poppet, or float, that is dropping down and allowing the water to flow out of the top of the vacuum breaker. Once the pressure is built up, the poppet is allowed to pop up and seat at the top of the vacuum breaker, and stopping the water from leaking. By city code, most cities require that the vacuum breaker be 18" to 24" above the highest head. Sounds like this particular valve has heads way above the vacuum breaker. One solution would be to raise the vacuum breaker. Another solution could be to feed the vacuum breaker with a line coming off your main water line to the house. Normally if it is being fed from a hose bib or 1/2" copper line, your volume (pressure) is probably not very good. If you can feed it with a 3/4" copper line or bigger, your volume will be much greater, and the vacuum breaker poppet might pop up on this particular zone with more volume. Let me know if I can be of any more help and have a great day.