does it drip from the front pin that makes the microswitch? if so then yes its a doddle to do and pretty cheap part. you need a hot water service kit, you get a nut and washer (where your leak is) o-ring and diaphragm.
they have been known to leak between divertor assembly and h/w section too tho, but as you said switch i presume you mean the front assembly.
power off, cold inlet off, remove switch, hot tap wide open, undo nut and free impulse tube off top, palm on assembly remove screws on circumfrance, its sprung so keep pressure on, change parts noting order/arrangement. nip up check for leaks then re-instate power.
ste, November 2009
