I installed a 30 psi pressure regulator down stream at the second garden bed not in use. Voila! It shuts off. This appears to be a pressure back up and the bleed caused by the low flow is not great enough to allow the valve to fully close. I am assuming that lawn sprinklers are adjusted to have a 30 or 50 psi regulation in their spring tension internally. If this is the case will not have the same issue if I added a low flow branch that had a sprinkler already on it?