We recommend placing a pressure regulator before the timer as pressure spikes or excess pressure from the supply line may cause damage to the valve when the valve opens. This can void warranty. Also keep in mind the placement of the unit as frost can cause damage to the internals of the unit, even if switched off for the winter and left out.
If pressure is an issue, we recommend a better-suited timer such as a 25mm valved unit such as a Galcon 7101, Hunter Node, Toro Tempus.