QuestionI live in Rapid City, SD. I bought a new house last fall that came with the front lawn sprinkler system already installed. The front spinkler system that came installed with the house runs on 3 zones, the backflow device is a Watts Model 800M4QT, and the 3 valves are Rainbird 100-DV. In the spring, I had a different company install the back yard sprinklers; they're also in 3 zones, but the valves thay installed are different than the front lawn--they are Rainbird Model CP-100. They all now run from the same timer/controller and through the same backflow device from the same water source in the house.
All summer I have had problems with water hammer near the backflow device. Any time the system initially turns on, no matter what zone starts first, there is a loud thumping noise that occurs at the backflow device, and water pours out of the bonnet. The only way to fix this is to briefly shut off the main sprinkler supply line (in the house near the water heater) and turn it back on, temporarily interrupting water flow to the sprinkler system...this seems to allow the system to 'catch up' and it works ok. But, when the system switches zones, I have to do the same thing all over again because the water hammer happens on every zone.
The irrigation company that installed the front 3 zones and the backflow device have raised the backflow device (now 15" above the highest sprinkler head), but the problem still occurs. They've also told me:
Too much pressure
Too little pressure
Not sure what's going on
I doesn't seem like they know what the issue is...their latest solution is to replace the Watts backflow device completely because they don't think it's working.
I'm at a loss, and can't seem to get any solid answers. Any help you could provide would be much appreciated!
Thanks,
Matt
Answer Matt, the backflow is doing what it is supposed to do. Water is trying to back up into the drinking water and it is dumping is off. The first thing I would check is to see if the water is on all the way. Maybe the valve(s) aren't open fully. If everthing seems to be wide open, then try this. With the system running close the output valve on the backflow slightly - less than half, less than 1/4 turn if possible. Then, even if the system doesnt run right see if the thing does the same thing when switchting zones. if it's behaving then the system is pulling too much water and it can't keep the poppet floating and either nozzles need to be changed to lower gpm or something. there may have been a chnge in the water pressure in the area. You could go to a different type of backflow, an rp, but that could be costly. Let me know, Jim
