The city is planning to spend $700,000 to find out exactly what kind of nasty fluids inmates are flinging at correction officers, it was reported Monday.

The forensic tests, included in next year’s budget, would investigate a practice known as “splashing” at Rikers Island, in which prisoners throw urine, blood, feces — and worse — at guards, the New York Observer reported.

The disgusting practice is a felony, and the proposed tests would help investigators find necessary evidence to punish offenders.

“If we can test whatever’s on the shirt or the uniform, it makes it a felony, a chargeable crime, rather than if it was water,” Correction Commissioner Joseph Ponte told the paper Monday. “So it increases the penalty to the inmate.”

It was not clear how many tests will have to be done, but Ponte described splashing incidents as “not common.”

But Norman Seabrook, head of the Correction Officers Benevolent Association, routinely tweets about such attacks.

“2 Cos [correction officers] splashed w/ feces-urine-blood,” he wrote on the union’s Twitter page Monday.