Valach made his official debut as an amateur cyclist at the 1996 Summer Olympics in Atlanta, where he finished sixty-eighth in the men"s road race by less than a second behind the peloton leader Abraham Olano of Spain, recording his personal best time in 4:56:48.
During his amateur career, Valach has claimed three Slovak titles in elite national championships (1997 and 1998) until having shown his great talent and passion for sport, he turned pro in 1999 with De Nardi – Pasta Montegrappa. When De Nardi – Pasta Montegrappa folded after the 2002 season, Valach was left with no contract. Competing under a freelance agent, Valach pulled ahead from a vast field of cyclists to dominate the road race at the 2003 Coupe des Carpathes in Poland in 3:57:03.
Valach signed a two-year contract with Editor" System ZVVZ in 2004 and eventually rode for Austria"s Aposport Krone Linz (AKL) in 2006.
He had solidified his lead by defeating the Austrian cyclist Michael Pichler at Völkermarkter Radsporttage road race, and also sprinted into a second-place finish at the second stage of Sachsen Tour in 5:52:17, trailing behind Great Britain"s Dean Downing by less than a second. Twelve years after competing in his last Olympics, Valach qualified for his second Slovak squad, as a 34-year-old, in the men"s road race at the 2008 Summer Olympics in Beijing by receiving a berth from the UCI Europe Tour.
Riding against his teammates Roman Broniš and Matej Jurčo, Valach remained as the only Slovak cyclist to successfully complete a grueling race with a sixty-second-place effort in 6:34:26. Valach"s official result was later elevated to sixty-first position, when Italy"s Davide Rebellin had tested positive for CERA that consequently stripped off his Olympic silver medal.
Following his success in pro road cycling, Valach extended his contract with Elk Haus–Simplon for another annual season (2008–2009).
Since he officially retired from sporting career in 2010, Valach has been currently appointed as the manager and head coach for Slovakia"s Dukla Banska Bystrica pro cycling team
In 2001, Valach became a Slovak champion in both road race and time trial at the elite championships, and thereby continued to defend both titles in the same tournament by the following year. Following a short demise from AKL and achieving mediocre results in numerous tournaments, Valach joined the Elk Haus–Simplon pro cycling team in the 2007–2008 season.
He represented his nation Slovakia in two editions of the Olympic Games (1996 and 2008), and later competed as a member of Dukla Trenčín–Merida professional cycling team before his official retirement in 2010.
