There should be several alternative ways to express what you want. For example, you can say "Try adjusting the sprinkler head / nozzle to produce a smaller water jet".

When you turn on the faucet, do your best to keep the flow at a minimum. Or, When you turn on the faucet, don't turn it too forcefully, as this will cause the water to spray out of the sink. Slowly adjust until you get the desired flow rate.