help on check valve configuration for backup sump pump
I bought a battery backup sump pump and need to know how to proceed on the check valve configuration. The current A/C pump has a check valve, but it's about 5 feet off the floor and the discharge line is bracketed to the wall. Discharge comes out of pit about 2 feet above floor before 90 deg. bend takes it to the wall. About another 3 feet up is the check valve.
I understand that if the main pump did not have a check valve prior to installing the backup, one needs to be put in for both pumps and the connection of the two discharge lines occurs above the check valves.
So I see 3 options, please let me know what is best, unacceptable, or offer another.
1) the one CV already in place is sufficient. Create a new discharge for backup sump and join the two about a foot or two from the floor.
2) cut the main discharge about a foot from the floor, install a CV for each pump and join the two above the CVs. Thus there will be 3 CVs in the configuration.
3) create new discharge for backup including a new check valve, cut the main discharge above its CV and join the two lines above the main CV.