its better to use seperate drain lines for each pump. this prevents a single drain failure causing a flood. but as I said earlier a gravity overflow drain to daylight is better.

I have a friend who bought a foreclosed home sitting on a hill that had a major water problem in the basement. he had 3 sump pumps and interior french drain installed. he felt safe........

I walked thru the home and suggested at least a overflow to daylight drain installed. He didnt want to dig up the yard

less than 2 years later he was on a trip, big storm took out power for 3 days. his besement filled with 5 feet of water. ruined lots of stuff.

he then installed the over flow drain.