Loss of pressure/volume

[Earl Bascom]

I recently had a plumber add pex for a bathroom remodel by tying into existing below slab copper. The next day we noticed the flow out of the existing guest bath shower was much lower than normal. I told them they must have kinked a pipe when they pulled the existing underground copper over about two feet which is needed due the new bath tub pending placement.
They assured me they did not kink the pipe, and indeed, I can't find any kinks. I can find some dents, however. Is it possible that dented pipe (3/4") would have noticeably less water flowing that previously?

 

[Reach4]

Slow shower for hot, cold, or both?
How is the flow from the lavatory (bathroom sink)?

 

[Sponsor]

 

[Jadnashua]

The id of 1/2" pex os closer to 3/8" copper. Depends on what volume you're trying to pull

 

[Earl Bascom]

Sorry, I did not give enough information. The new pex, has no bearing on the challenge with the lack of flow. The new construction is only in rough in phase.
The old underground copper previously came up through the floor between the toilet and old shower location. That old location will have a drop in tub when construction is done. The old pipes came up and back down for the next bathroom supply lines with T-s for the shower and w/c.

I am attaching two photos. One at the end of day 1 when the problem was noted to the plumber. The second photo shows their completed work.

The way the problem manifests itself in the hall bath is what has us baffled. The flow starts as it always did but then within 30 second drops off to about half the volume. I have disassembled the shower valve and flushed it as well as the shower head. The bathroom sink also shows the problem but is less obvious than the shower. It seems to be both cold and hot water. One strange thing that has happened twice. There seems to be no cold water at all and then suddenly it comes back on. There are no other water using events on the property when this happens.
Thanks for your considerations, in advance.

 

[Jadnashua]

It's possible that some crud got into the pipes when the work was done. ON the sink, take the aerator off and turn the water on to see if it can flush out any crud. You might take the showerhead off and try that, too. Some faucets and valves have inlet filters, and the filter may be clogged. Could be other things, but check those first.