That version of this tale has been around for over 25 years and other versions for longer than that.
urbanlegends.about.com/library/bltoilet2.htm
Sometimes it revolves around him mowing the lawn and crashing through the patio doors and older versions feature an outside toilet. 
Here’s one that dates back to the 1950’s
Granddaughter was cleaning the tool shed when she came across a partly used gallon can of gasoline. The family was of meager means, so she thought that it would be a thrifty thing if she could find some use for the gasoline. There was no car in the family, but there were many things which could be cleaned by gas. Granddaughter decided to clean the privy.
She scrubbed the walls, the door; the dessus de toilette. Everything was spick and span.
No sooner had Granddaughter finished than Grandpappy came down the path toward the privy. His glasses were perched on his nose, his pipe was cocked in his mouth, and a copy of Over Sexteen was tucked firmly under his arm. Just before he entered, he struck a match to light his pipe. A deafening explosion filled the air.
Granddaughter rushed to the scene. The privy door was blown off. The walls were blackened and shattered. She found Grandpappy sprawled in a clump of bushes about fifty feet from the site of the explosion. His glasses hung from one ear, a pipe stem drooped from his mouth and the book, torn and battered, was still tucked under his arm.
“Grandpappy,” she screamed, “what happened?”
“I dunno, Granddaughter,” he replied, “it musta been somethin’ I et.”