Underslab DWV

Planning new construction with basement bath and washing machine.

Proposed arrangement of trenched-in DWV is attached. Sweeps, combos, and wyes will be used where required, and vent fittings will be rolled up at least to 45.

Do I need a backwater valve in the sewer branch that serves all the basement fixtures? If so, I can put one in the main line where noted, and have it be the type with an integral inspection and cleaning stack.

Is there anything you would change in the arrangement?

Are you using an ejector or is the sewer entry beneath slab?

No ejector

The sewer lines come through the slab and the mains run under it and out to a septic tank.