I finished making my fox (and cat) scarer using one of those noisy impulse water sprinklers. This is controlled by a PIR which activates a 12v solenoid valve connected to the garden hose that then connects to the sprinkler.

It works a real treat but the problem is that solenoid slams shut instantaneously. This sends a shock wave back through the water system. And the result was that the shock waves caused a water leak at a junction of the incoming water supply from the street.

My question is to find out if there's an easy way to overcome the shock wave problem - either by:-
1. Electrical solution to close the solenoid progressively - whilst still making it open instantly.
or
2. Some mechanical means in a pressure vessel or whatever?

All suggestions are welcome.