Beast, It sounds as if the two "nozzles" (test cocks) you speak of were opened up in order to drain the backflow preventer of water in preparation for winter. I think it's an easy fix by simply closing the two test cocks. Most test cocks are manipulated by a flathead screwdriver. The caps are there merely to keep debris out of the threads of the test cocks, not for a seal tight fit. All Wet Texas Licensed Irrigator #1897 since 1984

You could try using one of the pressure regulators they sell for drip irrigation that connects to a hose bibb. Go to the drip irrigation system section of any of the big box retailers. The only thing to lookout for is the threads. There's hose bibb threads and pipe threads. With most hose-connected drip irrigation systems, you start at a hose bibb (hose threads). But many times, as you put the pieces together, you jump to pipe threads. See, a typical drip irrigation kit will consist of a backflow preventer, pressure regulator, filter, and tubing adapter designed to be put together in that order. That means the Backflow preventer will have hose threads on the input. But the output of the backflow and all the other connections in the system could be either. So you might have to find some male/female, hose/pipe thread adapters. Here's an example of what I'm talking about. http://www.mrdrip.com/pressureregulators.htm The standard regulator looks like it has pipe threads on the output, but the input might be hose threads. If I'm right, you would need not only this pressure regulator, but also a male-pipe to female-hose adapter. You would connect the pressure regulator directly to the hose bibb, the adapter to the regulator, and your hose to the adapter.

rem, You didn't introduce added pressure but with the added flow demand through the BFP you are probably hearing the noise cause by higher velocity than the fixture is designed for. Increase the size to a larger BFP and the noise should go away. The Flow is equal to area of BFP opening times velocity through that opening. If flow rate(demand) increases the opening stays the same then the velocity has to increase. This also causes water hammer when in your system when auto valves close suddenly. WH can cause damage to valves and can cause cracks in the pipeline. Just a thought. JMHO Aloha

I have a situation very similar to Toffee1's. I want to add an additional drip line to the balcony from the existing irrigation system. The existing system has a shut off valve connected to the water supply. After the shut off valve is a pressure vacuum breaker (Wilkins model 720A) which then connects to 3 control valves (one for the lawn, one for trees, and one for shrubs). I simply made a new branch from the 1/2" black ploy tube off the shrub line to the foot of the house (about 10 ft). Then I plugged in 3 micro-tubes (1/4") into the poly tube and pulled them up to the balcony. Water pressure is good enough when it reaches the balcony. However now I just realized I will have about 10 drippers on the balcony. These drippers are located much higher than the Pressure Vacuum Breaker. I wonder how likely this is going to cause the PVB to malfunction. If I add an inline backflow preventer (you can buy it from Home Depot for just a few dollars) on the new poly tube will it solve the problem? I am looking forward to hearing from you experts :)