Anyone know what the typical inside wall diameter for house drain pipes were with this place was built in the mid-1960's? I'm talking about the drains under the house (inaccessible in this one) - from the toilets to the main drain connection, and the main from the house to the street.

The drain from the washer to the main drain is the only one I can see, and it's standard 1-1/2 inch pipe -- smaller than they install these days.

Snuffy