Don't try to name every scenario, just state that if the clog isn't caused by roots or a collapsed sewer line then tenant will be charged for cost + admin fee. 

They will get married have kids want to plant roots  will understand that rent is throwing money down the tubes and will go looking for housing to buy. 

This is a fairly common issue with older properties  where root structures create a dislocation in the line causing constant backups and the only remedy is replacement.

Tenant also agrees to the following:-All drains, waste pipes, and plumbing are accepted as clear by Tenant at the time of occupancy, and any material blocking them after occupancy shall be repaired at Landlord’s cost, unless determined by repair person that such blockage occurred during the time Tenant controlled the Premises and due to some fault or negligence of Tenant, specifically excluding blockages caused by roots or backups from the street.

Offsets, root/soil intrusion and some build-up in the pipe.

(Hey I was rooting for Denver!

Rooting for you, thank you for your service, and let us know how we can help!

This is a family that has lived in Oregon FOR DECADES and has a lot of roots in the area.

The property is in an older part of Colorado Srpings with mature trees and the roots have breached the pipe creating a hole.

@Geoffrey HoffmanI am rooting with Geoffrey here.