Urgent!!! PVC Shower Pan and Screws Piercing the Membrane - Will This Cause Leaks?

I am having my shower torn out and completely rebuilt.
The trademan who is doing this has installed a PVC liner 7 inches up the sides of the shower from the and over the curb.
However, when he installed backer board over the PVC liner, he installed screws into the backer board that were between 1.75 and 2.00 inches above the bottom of the liner where it rests against a sloped subfloor, piercing the PVC liner at that point behind the backer board.
He intends to lay down a layer of mortar on top of the PVC liner to create a sloped surface to lay the floor tile on. Thus, the height of the screw holes (and the punctures in the PVC membrane) will be even closer to the finished shower floor after the file is installed.
This trademan says that he installed a bead of caulk to prevent the PVC liner from leaking where the screws penetrated the liner, but I am extremely concerned that integrity of the PVC shower pan has been compromised by the screws that pierce it.
It is my understanding that the PVC membrane should NOT have been punctured at a point so low.
I would also like to know what would happen if the PVC membrane on top of the curb is pierced by screws when backer board is installed on top of the curb. Will screws piercing the membrane on top of the curb create a potential for leaks as well?
What is the appropriate way to fasten backerboard when a PVC liner has been installed?
Am I justified in being concerned about the potential for leaks?
Please respond ASAP as the trademan has not installed the tile yet, but plans on doing so very shortly.
Thank you.
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Try posting it several more times.
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Al wrote:

Do you plan on having 1.5" of water sitting in your shower stall on a regular basis? If not, I wouldn't worry about it.
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The screws piercing the PVC membrane are 1-3/4 to 2" above the PVC membrane lying on the subfloor, but on top of the PVC liner a sloping mortar bed will be added as one cannot place tile directly over the PVC liner.
This means that after the tile on the shower floor is installed, the screw holes will be much closer to the bottom of the shower floor than the 1-3/4" to 2" that I listed in my original email.
Sorry for posting my inquiry so often. I had posted it and deleted it several times - each time revising it a little.
Thanks.
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deleted it

As you have learned, deletes rarely work.
Bob
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The screws piercing the PVC membrane are 1-3/4 to 2" above the PVC membrane lying on the subfloor, but on top of the PVC liner a sloping mortar bed will be added as one cannot place tile directly over the PVC liner.
This means that after the tile on the shower floor is installed, the screw holes will be much closer to the bottom of the shower floor than the 1-3/4" to 2" that I listed in my original email.
Sorry for posting my inquiry so often. I had posted it and deleted it several times - each time revising it a little.
Thanks.
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And now you posted this more times. Learn how to use a computer !!!!
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Al wrote:

This link has details of shower installation, and suggests your concerns are right:
http://www.thetiledoctor.com/howto/showers.cfm
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