Air admittance valves

I just inspected a house that had 3 air admittance values on the same waste pipe along a 20’ length. There are in a basement ceiling right up against the floor insulation. Is this okay? Also, the 1 1/2" waste pipe reduces down to a 1" waste pipe as it exits the foundation.

Thanks for any help,
Russell Truluck

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Can you day “do over”?

I’m pretty sure my daddy (50 yrs master plbr) said you can’t bottleneck a drain or a vent. And don’t they believe in vents.