The oil paintings belonged to Cambridgeshire businessman Tony Thompson, who had collected Lowry's work since 1982, and died last year.
A painting of Piccadilly Circus in London, for which Mr Thompson paid £5.6m in 2011, was the biggest draw of the night - selling for £5.1m.
Thirteen paintings were sold, but two failed to meet their reserve price.
Mr Thompson was born in 1945 in Trumpington, on the outskirts of Cambridge, and lived in the surrounding area all of his life.
He started his recycling business when he was 14 and went on to become a millionaire.
He began collecting paintings by Lowry in his late thirties, when he made his first purchase at auction.
Entitled Street Musicians, the work portrays a scene in Thurso, Scotland, and was painted in 1938. It cost £17,600 32 years ago, but sold for £842,500 at Sotheby's.
The auction house said Mr Thompson had become the first person to bid more than £500,000 for a Lowry painting, when he bought the smaller of two pictures of Piccadilly Circus in 1998.
Source: Sotheby's
He secured the larger version in 2011, when he broke the record for a Lowry.
His sister Dawn Saddler, said his love of the Manchester artist's work began in childhood.
"He just loved Lowry - the man and the paintings," she said. "As the obsession grew he collected and collected.
"He was a simple man, just like Lowry."
Frances Christie, Sotheby's head of modern and post-war British art department, said Mr Thompson was a "collector who truly understood Lowry's vision".
"He had a real instinct to hone in on the very best examples of the artist's work," she said.
"When it came to Lowry, he knew everything."
A collection of paintings by LS Lowry has sold at auction, for a total price of more than £15m.