Hello sandy_yago, I am not an expert on drip irrigation systems and
have never installed one. However, I do know something about
hydraulics. I am very surprised that the Lawn Genie experts were not
able to answer your question. At first I didn't understand what the
term "anti-siphon" meant in the valve description. I assumed that it
meant the valve prevented siphoning of water to the sprinkler heads
after the syatem shuts off. After reading some on the Lawn Genie
website I determined that I was wrong. The "anti-siphon" feature
prevents water from siphoning back into your home water system should
should there be a loss of pressure (backflow prevention). Your problem
is exactly the opposite. When the system shuts off water gravity feeds
the sprinkler heads until all water has drained from the system. Lawn
Genie does not address this problem except for telling you to not
install a sprinkler head (emitter) more than 6 inches lower than the
valve. I searched for an inline check valve to install down stream
from the Model 54000 valve and found one on the Rain Bird website:
http://www.rainbird.com/drip/products/control/check_valves.htm
Check Valves
Control Zone Components
Features & Benefits:
Prevents water from draining upstream of check valve or back into valve box.
Use with a Back Flush Filter when filter is at a lower elevation than
the rest of the system.
Operating Ranges and Specifications:
Pressure: 20 to 120 psi (1,4 to 8,3 bars)
Threads:
- CV-075: 3/4" FPT x 3/4" FPT
- CV-100: 1" FPT x 1" FPT
Models:
CV-075
CV-100
Rain Bird does allow for your problem and the 3/4 inch version of the
valve could be exactly what you need. The reason I say could be is
that they don't say what the opening pressure rating is for the valve.
I assume that since they show the operating range is from 20 to 120
psi that the valve will hold against 20 psi of siphoning pressure
which is plenty for your layout. I am sure that your local Rain Bird
dealer can answer that question for you and recommend another check
valve if this one is not adequate. With your 10 foot elevation
difference you need a valve rated for at least 5 psi. The check valve
needs to be mounted immediately after the Model 54000 valve with the
flow arrow pointing toward the emitter (down stream). Then when the
system shuts off the check valve will close and hold water in the line
preventing additional flow. This is good for another reason also. It
prevents a water hammer situation whan the line is dry and water
rushes in as the system comes on. I think I have covered everything,
but please ask for a clarification if I haven't.
Good luck, Redhoss |
