Ffynnon Llandyfan is located immediately north-west of St Dyfan's Church (NPRN 302028), in the north-west corner of the churchyard. Llandyfan House (NPRN 17508), sited immediately south of the Church, was reportedly an inn in the eighteenth century, said to have been used particularly by pilgrims visiting St Dyfan's well. According to tradition, the water was known for curing paralysis and similar ailments. The well was reputedly popular with pilgrims, and in the early eighteenth century magistrates reportedly found it necessary to suppress unseemly dancing and game-playing there on Sundays. When the site subsequently became non-conformist, the well became a baptismal pool. After the site reverted to Church of England use, people reportedly continued to drink the waters from a skull alleged to be that of St Teilo.It is noted that he waters of the well have since been diverted into a reservoir serving Llandeilo.

The rectangular pool is Grade II listed. It was rebuilt in 1864-1865, probably to the designs of R.K. Penson, who designed the rebuilding of the church. The structure is 2m deep and lined in red sandstone ashlar with low walls coped in grey limestone. A flight of stone steps leads down to a shallow rectangular pool, with an inlet on the north side and outlet on the west.

Sources include:
Cadw, Listed Buildings Database
www.llandeilo.org
www.readperiodicals.com

N Vousden, RCAHMW, 17 January 2013