HOUSTON -- Evan Gattis smacked a tie-breaking home run in the bottom of the eighth inning, his second homer of the game, to lift the Houston Astros to a 7-6 victory and a four-game series sweep of the Seattle Mariners on Sunday at Minute Maid Park.

Houston (18-7) extended its winning streak to 10 consecutive games in somewhat unconventional fashion, coughing up a five-run lead before Gattis struck against Mariners rookie right-hander Carson Smith (0-1), who allowed the first run of his career. Smith had not been scored upon in 20 career appearances.

The Mariners (10-15) trailed 6-1 courtesy of Gattis' three-run, first-inning home run off left-hander J.A. Happ, and a two-run blast from Astros first baseman Chris Carter in the third, a shot that scored Gattis. Houston tacked on its sixth run when shortstop Marwin Gonzalez singled to right in the fourth, scoring catcher Jason Castro from second.

Astros right-hander Roberto Hernandez pitched effectively enough, but was undone by his infield defense. Gonzalez was guilty of a throwing error in the sixth inning that enabled Seattle right fielder Seth Smith to score following his triple to center field. Still, the Astros led 6-2 entering the seventh inning before Hernandez allowed three consecutive hits.

Mariners catcher Mike Zunino chased Hernandez with his RBI double, scoring third baseman Kyle Seager. Seattle pinch hitter Rickie Weeks followed by greeting left-hander Tony Sipp with a two-run double to center, pulling Seattle to within 6-5. Another Houston error followed.

With Mariners center fielder Justin Ruggiano batting, Astros third baseman Jonathan Villar failed to catch an accurate throw from Castro with Weeks bearing down on what was an ill-fated attempt to swipe third base. When the throw sailed past Villar, Weeks rounded third and scored easily, taking Happ off the hook and tying the game at 6-6.

Astros closer Luke Gregerson induced a game-inning double play from Mariners shortstop Brad Miller to record his sixth save. Pat Neshek (2-0) notched the victory for Houston.

NOTES: Following his third multi-homer game of the season on Saturday night, Mariners DH/RF Nelson Cruz is batting .407 with 11 home runs and 21 RBIs while in the lineup as the right fielder (15 games). Cruz batted fourth as the designated hitter on Sunday. ... Astros 2B Jose Altuve closed the opening month with a .500 slugging percentage, his highest such mark since entering May of 2012 -- his first full season in the majors -- with a .547 slugging percentage. ... Seattle entered the series finale with 24 solo home runs, the most in the majors. ... This is the latest Houston has been in first place since May 22, 2004.