One of the reasons Colonel Pyncheon chooses this particular acre to steal from his neighbor, Matthew Maule, is that there is a spring of fresh water on the property. But as soon as Colonel Pyncheon starts to build his new house, the spring suddenly becomes polluted. This seems to be a sign that the house is cursed.
Maule's Well also symbolizes the persistence of Matthew Maule's memory in the Pyncheon family. No matter how much they try to make the House of the Seven Gables their own, Matthew Maule is always bubbling up in the garden. After Judge Pyncheon dies in the same chair that Colonel Pyncheon passed away in so many years before, Maule's Well "[overflows] its stone border, and [makes] a pool of formidable breadth in that corner of the garden" (19.58). Perhaps Maule's Well is overflowing in celebration because Judge Pyncheon, like Colonel Pyncheon before him, has been given "blood to drink" (1.4).
When Clifford sits in the garden, he often looks into Maule's Well. He claims to be able to see "shapes of loveliness" in the water, which are now and then disturbed by "a dark face" (10.14). Phoebe believes these "shapes" to be the result of Clifford's imagination, with his cruel fate symbolized by "the dark face." But who knows – the novel ends with Maule's well sending up visions of the happy future of Phoebe and the rest of the surviving Pyncheons. Perhaps it does give us a glimpse into the past and future. After all, one of the Maule family's mystical abilities is supposed to be unusual clear-sightedness about dreams, visions, and the like.
One tiny, rather romantic note: when Mr. Holgrave plucks some of Alice's Posies from the roof he tells Uncle Venner, "I have heard [...] that the water of Maule's Well suits those flowers best" (19.12). We have discussed the ways in which Alice Pyncheon is linked to Phoebe in "Characters." And Mr. Holgrave is a descendant of Matthew Maule. So maybe this is a nice bit of foreshadowing of Phoebe and Mr. Holgrave's love: Phoebe is represented by Alice's Posies, and Mr. Holgrave is the water from Maule's Well.