Routine issues such as a clogged drain, the plumber should report what he pulled back, if anything, and how far out was the blockage.

For example, my lease states: “Tenant shall be charged for repair of drain blockages or stoppages, unless caused by defective plumbing parts or tree roots invading sewer lines.”

It could also be indicative of a blockage in the vent.

Frozen water supply pipes in the kitchen at one rental and also a drain blockage at the same rental where the blockage was determined to be frozen.And today had an inspection on a flip with guess what - frozen water supply pipes in the upstairs bathroom.Lucky for me I can solve the frozen supply pipes at both houses using a hot water recirculation system, where when the water temperature in the pipes gets too low a valve opens to mix some of the water from the hot pipe into the cold line; this keeps hot water in the hot pipe much hotter (no longer need to run the water for a long while to heat it up), and sends warm water into the cold pipe so that the nearly frozen water flows back to the water heater to be reheated.

Looking for recommendations as I have a house that has a sanitary backup in the basement due to a blockage.

When I was on vacation the out of the country the Saturday after this past Thanksgiving, a tenant called me because the 1st floor toilet was overflowing and she didn't know what to do; there was a sewer line blockage and the basement washing machine was trying to empty so the ejector pit was now ejecting through the first floor toilet...  

I had one of those back pressure sewer valves put in $500 installed.It made a BIG difference as the insurance co didn't want to include coverage as the home had a claim in the past (b4 I owned it, & the city sewer backup was not the fault of the home owner).In my area if it happens you're responsible for the temp accommodation of the tenant(s) until it's cleaned up.Since then the only blockage we had was viewed via camera & found to be a city clay sewer pipe collapse.

Now that they have their new dryer in place they have discovered the blockage of airflow and they want us to fix it.My first thought was, did they check the vent to make sure it wasn't clogged PRIOR to buying a whole new unit?

I would think if there was some blockage in the toilet there would be a back up.

But, I wouldn't be so fast to assume anything unless I saw on camera what the blockage is.