This is the last week in which you can water heavily. Once pinheads appear, water sitting on them marks and spoils them, so the casing must carry its reserve before that. ICAR-DMR wants about 50 plus or minus 2 percent moisture in the casing at pinning.
Water little and often rather than once and heavily. Water that runs through into the compost does not come back and drives out air the mycelium needs. Judge by lifting a pinch from three places: it should be damp all through, not wet on top and dusty underneath.