NBC WILL AIR `SEINFELD' FINALE AGAIN WEDNESDAY.

Byline: Keith Marder Daily News Television Writer

Apparently 108 million viewers weren't enough.

Less than 12 hours after the cellblock doors closed on the ``Seinfeld'' characters, NBC entertainment President Warren Littlefield announced that the network will present an encore airing of Thursday night's mega-hyped series finale.

The repeat presentation is scheduled to air at 8 p.m. on Wednesday, which, coincidentally, is the final day of the May ratings period.

Littlefield said that by eliminating network promotional spots, the 75-minute show will nearly fit in a one-hour block.

``Although millions of people enjoyed Jerry Seinfeld's farewell last night, our phones have been lit up, and we're aware that millions of other `Seinfeld' fans weren't able to watch this historical TV event,'' Littlefield said Friday. ``We hope that telecasting it on another day and time will give these folks a chance to experience the magic that Americans across the nation will undoubtedly be discussing at water coolers today.''

According to Nielsen Media Research, the show earned a 47.7 rating and 62 share. Approximately 90.7 million people in America watched at least part of the show.

And on any given minute Thursday night, an average of 76.3 million people were tuned to ``Seinfeld,'' ranking the episode sixth on the list of most-watched entertainment shows of all time.

On Feb. 28, 1983, the finale of ``MASH'' attracted an all-time-high average audience of 106 million. It was followed by the ``Who Shot J.R.?'' episode of ``Dallas'' (Nov. 21, 1980), which had an average audience of 80.4 million; the finale of ``Cheers'' (May 20, 1993), which had an average audience of 77.4 million; ``The Day After'' (Nov. 20, 1983), which had an average audience of 77.4 million; and the eighth and final segment of ``Roots'' (Jan. 30, 1977), which had an average audience of 76.7 million.

The highlight show leading into the ``Seinfeld'' finale had an average audience of 73.2 million ``in-home viewers.'' And ``The Tonight Show with Jay Leno,'' which featured appearances by Seinfeld and surprise guest John F. Kennedy Jr., attracted an average of 24.1 million viewers.

NBC's research department later bumped the official Nielsen figure up to 108.7 million in its own estimates, accounting for an additional 18 million viewers who network researchers presume watched the program at ``out of home'' venues - college dormitories, hotels, restaurants, military bases, health clubs and hospitals - that are not included in the Nielsen sample.

Roughly half the Los Angeles market (about 7 million out of nearly 14.8 million viewers) was tuned in to the historic program. That's more L.A. viewers than ``Cheers'' garnered with its farewell five years ago.

The folks at the Department of Water and Power can prove that Los Angeles was paying attention.

There was a 35 percent spike in water usage when the show was over at 10 p.m., and there were also 10 to 15 percent spikes in usage during commercial breaks.

``It was very significant,'' said spokesman Walter Zeisl. ``Overall, water usage was consistent to a normal day, but . . . a pattern like that is extraordinary. The patterns of usage corresponded precisely to the commercial breaks.''

Despite a police spokesman's hopes reported earlier this week, the heavily watched television show did nothing to curtail crime or vehicle crashes.

According to LAPD spokesman Jason Lee, there were 454 emergency 911 calls and 656 incidents reported on Thursday, compared to 455 calls and 620 incidents on Wednesday.