There is a way to pin down a more detailed location for this Killigrew household within this(*) Knockanpower Lower townland in 1901 & 1911, which involves using the records in the Valuation Office in Dublin city (Lower Abbey Street) i.e. the Revaluation Records aka Cancelled Land Books.
There are no Killigrew properties shown at this townland at the time of the primary valuation which is dated 1851 for this area, so seems your Patrick took over the property some time after that. The Cancelled Land Books continue on from Griffith’s and detail changes in the properties and alterations relating to the occupier and lessor. The records for some counties have been digitized and are available on computers in the office, but searches for Co. Waterford currently require checking the original books.
The volumes for rural areas are listed by Electoral District, civil parish and townland and each one covers about 10 to 20 years of changes, with different coloured ink used to indicate different date. The same plot numbers carry forward, so you can usually use the original Griffith maps so figure out the location of each property - the Valuation Office hold more recent maps.
Entry for Knockanpower Lower (Ringagonagh) with map from the Placename database.
* There are two separate townlands in Co. Waterford named Knockanpower Lower, the one where your Patrick lived is in Ringagonagh civil parish near the coast south east of the town of Dungarvan. The other Knockanpower Lower townland is in Colligan civil parish and well to the north of Dungarvan.