Presiding over a company with a market value of US$ 143 billion apparently gives Silicon Valley’s most famous billionaires a good sense of humour.

Senior executives at Google Inc launched their annual April Fools’ Day prank yesterday, posting a link on the company’s homepage to a site offering consumers free high- speed wireless Internet through their home plumbing systems.

Code-named Dark Porcelain, Google said its Toilet Internet Service Provider (TiSP) works with Microsoft Corp’s new Windows Vista operating system. But sorry, septic tanks are incompatible with the system’s requirements.

The gag included a mock press release quoting Google co-founder and president Larry Page, an online installation manual, and a selection of frequently asked questions. On some Google sites, the company’s logo — a multicolored “Google” that changes according to the season and on holidays-substituted a toilet for the second g.

“There’s actually a thriving little underground community that’s been studying this exact solution for a long time,” Page said in the facetious statement. “And today, our TiSP team is pleased to be leading the way through the sewers, up out of your toilet and splat - right onto your PC.” Marissa Mayer, a Google vice-president, called TiSP a “breakthrough product, particularly for those users who, like Larry himself, do much of their best thinking in the bathroom”.