As far as I know, the back flow preventer is required to be installed by the manufacturer
, but you are not legally required to keep it.
Is it necessary? That was debated here not long ago with no consensus reached.
You could replace the valve to stop the leak.
Another possibility would be to wrap the valve in a towel to stop the drip. The towel would absorb the drips and they would evaporate. Of course that would not work if the valve develops a serious leak.
Hope something helped.
Sherm & Terry w/rescue Eydie (min Schnauzer) & Charley (std Poodle)
2015 Jay Flight 27RLS, GY Endurance (E), Days: 102 '15, 90 '16, 80 '17, 161 '18
2006 Ford F350 PSD, 4WD, CC, LB, SRW, Cmpr. pkg, Equal-i-zer 4-p, Continental ContiTrac TR