TOKYO (AFP) - Armchair Japan fans following their team's 2-1 World Cup Group H win over Colombia risked triggering a plumbing disaster of biblical proportions when millions rushed to the toilet at half-time.

It was a case of squeaky bum time when fans finally tore themselves away from the TV earlier this week after a nail-biting first 45 minutes, with water use jumping 24 per cent in Tokyo during the break, the city's waterworks bureau said on Friday (June 22).

"We presume it's because a lot of people (who were) holding off on a trip to the bathroom all went at once," an official told AFP.

"Water use can fluctuate, especially during football matches, which only have one break in the middle," she added. "It also can be affected by a period of time, excitement and other factors."

Flushed with joy after watching Yuya Osako bag a second-half winner for Japan against 10-man Colombia in Russia on Tuesday, jubilant fans made another dash for the loo at the final whistle, causing another spike of 50 per cent in water use.

But the official revealed the Tokyo waterworks bureau had anticipated the stampede, and adjusted the city's supply and pressure accordingly in order to avoid catastrophe.

"We are ready to prepare for a stable water supply during the next match on Sunday," she insisted, looking ahead to this weekend's clash with Senegal.

A similar pattern of toilet use was noted across Japan as viewers remained glued to their screens for the match, broadcast live on prime-time TV.

The viewing rate for the fixture also hit a yearly high of 48.7 per cent in Japan, surpassing the 33.9 per cent marked when Japanese figure skating hero Yuzuru Hanyu won Olympic gold in February.