They did a crap job.

Buckets of water poured into an exclusive Upper East Side apartment and caused a million dollars in damage after the upstairs residents’ toilet repair went horribly wrong, according to a new lawsuit.

Roberto and Maria Bonetti caused the pricey deluge in the Park Avenue building by allegedly over-tightening a toilet and causing a crack below it that led to a massive leak, according to the documents filed in Manhattan Supreme Court last week.

The insurance company for Ralph Joel, the owner of the flooded unit, is seeking $1,006,655.50 plus interest for the April incident.

The Bonettis failed to inspect the plumbing and should have been aware of the need for further repairs and replacements, the suit charges.

Units in the landmarked 876 Park Ave building, which was built in 1917, go for $6 million.

There are only two units per floor and listings for the posh pads advertise wood-burning fireplaces, large rooms and high ceilings.

Joel’s lawyer declined to comment.

The Bonettis could not be reached.