Children from Killossery School, whose folklore was collected as part of the Irish Schools' Scheme, recorded the local tradition: St. Margaret, finding no other water, washed her cap in this well, and ever since the water has come up boiling. What the folklore calls boiling, the chemist would call something more prosaic, but the effect was real enough. The well was a tepid, perpetually bubbling spring that, according to a description from 1897, never froze.

The mineral composition was part of its reputation. Writing in 1838, D'Alton recorded that the water contained lime, muriate of soda, nitrate of kali, and sulphur, a combination that kept the temperature of the water consistently warm and gave it the medicinal qualities for which it was frequented. The well was enclosed, probably in the sixteenth century, by Sir John Plunkett of Dunsoghly, who died in 1582, to create a bath; a plaque on the west end of the tank, erected by Farrell and Son in 1975, records this. The enclosure itself, a stone-lined basin approached by steps from the south, with a stone wall, iron railings, and a gate, looks considerably later than Plunkett's time, though the wall he built is said to be still standing. The dedication adds another layer of uncertainty: the 1837 Ordnance Survey six-inch map names it St. Margaret's Well, but by the revised edition of 1863 it had been rededicated to St. Brigid. Whether the change reflects a local shift in devotion or simply a cartographer's correction is not recorded.

The well sits behind the Roman Catholic chapel, to the east of the Fair Green in St. Margaret's village. Access is via a laneway from the rear of the Parochial Hall. The church and graveyard associated with the site lie some 300 metres to the north-east. Visitors should be aware that the well began drying up roughly twenty years ago, and the base is now grassed over rather than water-filled. What remains, though, is the enclosure itself, the steps, the stonework, and the railings, enough to understand what the 1897 account described as a spring that once bubbled visibly from the bottom every minute.