Jay, it sound like you have a blockage in your shower drain.

But remember that clause in the lease about how the tenant is responsible for foreign object blockage in the plumbing system?

Affordable Plumbing came in and found the faucet center caps had fallen into the drain and causing the blockage.

We have Enphase microinverters, so if there is some blockage, we still get power. 

Do the toilets inside flush without any blockage if you pour a bucket of water into the toilet, same for the sinks and any floor drains,?

Check out this picture of a root blockage at our AZ property....and this was under a driveway too!?! 

Many times I have gone to a rental to clean a drain for a landlord and he is sitting there watching and waiting for me to pull the snake out to see what caused the blockage.

t=484690Galvanized water supply is something I don't like, because the pipe is corroding from the inside, and eventually the corrosion can lead to blockage of the pipe.Iron waste pipe is somewhat more modern than alternatives like say clay ...

When the water is turned off enough pressure builds up past the blockage to provide pressure for just a moment when the faucet is turned on.  

He found no issues with it and said there was probably a temporary blockage in the flue/chimney that worked it's way out.