ok you have flushed out the difference between these two neighborhoods but what does the math tell you? 

For tenants you need to tell them not to flush anything but tp.

@Susan K. like the tenant we had that kept flushing cat litter down the toilet.

I called a plumber.....they came out to fix it.....Now everyone is happy.Since you're in the East Bay like me, I would suggest you have your property manager in Cleveland give the tenant 24 hour notice that they are going to come into the property to see if they can figure out what's going on......They may find or hear something that may not intially be visible but if they run some water faucets and or flush the toilets and water keeps dripping or running afterwards you can start to get to the root of the problem. 

Builders seem to be flush with cash after selling their spec builds effectively.

Some I would check would be Sterling National, Flushing, Emigrant, Valley National, Bethpage FCU.

The water pressure is mostly noticeable when you flush the toilet and the pressure in the rest of the apartment drops.

The bathroom must have a 5' turning radius, the sink must be wall hung or open cabinet( 34" to top rim), the toilet must have the proper grab bars installed and at certain heights, the flush handle on the toilet must face the side that has the 5' turning radius not the opposite side.

I would flush the money that is owed to you. 

They might flush a toilet or look under the sink but the plumber is the one to scope the toilets and check the whole plumbing system including to the street.