They just had to plunge really hard and all the sudden it drained.

Also train them on how to use a plunger.  

Tenant agrees to pay for clearing the drains of any and all stoppages except those, which the plumber who is called to clear the stoppage will attest to in writing, were caused by defective plumbing, tree roots, or a result of weather.Tenant agrees to keep on hand and properly use a plunger when necessary to unclog drains and to prevent water overflow from toilet, sinks and bathtub.

Make sure they know how to use a plunger.

Tenant agrees to pay for clearing the drains of any and all stoppages except those, which the plumber who is called to clear the stoppage will attest to in writing, were caused by defective plumbing, tree roots, or a result of weather.Tenant agrees to keep on hand and properly use a plunger when necessary to unclog drains and to prevent water overflow from toilet, sinks and bathtub.

We give them a handful of documents along with the lease (i.e. a lead disclosure and what not) and also leave a "move in gift" which is mostly cleaning supplies, a cheap plunger and the like (hint, hint).

I don't choose tenants, I don't deal with plungers and I don't collect rent.

Tenants know they need to use a plunger.

Don't forget the sink plunger and de-clogging a tub drain....

{Just this spring, we started adding a CD with soft copies of all this information to each binder} Once I get time, we'll put all of this on-line.We also provide a new toilet brush (I buy them by the case when they are on-sale for $2.99 each), a plunger, shower curtain, and a tray of cleaning supplies under the kitchen sink whenever a new tenant moves in.This costs us around $30 per turnover.