We have two separate shower heads (not shower/tub combo units) that intermittently drip. Sometimes several days will pass between drips, and other times it will drip for 30 minutes, stop for an hour, drip for an hour, etc. Recently, we accidentally left the water in the on position in our third tub/shower with a dog wash sprayer hose attached. During this time, the other two showers did not seem to drip, but as soon as we turned the water off and released the pressure in the third tub/shower the drips returned in the other two showers. If it helps, one shower head is from the Price Pfister Ashfield series (relatively new) and the only info I can find on the other is Delta, 1700 Series, Monitor (probably about 4 years old). Thanks.