Pressure-balancing Moen shower-tub valve releasing hot water in the "cold" position
The 16 year-old building of 45 one-bedroom apartments I live in has just had a complete repiping: all old copper pipes replaced with PEX ones, old shower valves replaced with new Moen ones (1085 aka 8370), sink faucets replaced, etc. After the work on my bathroom was done, I noticed that the water coming out of the bathtub faucet upon opening was not cold -- as one would expect, when sliding the lever counterclockwise from its closed position at the bottom -- but hot, and grew cooler as one moved it counterclockwise to the 3 o'clock position on the right. From that maximum coolness (note, just "cool," not cold!) at 3 o'clock, the water then became warmer again until it reached maximum warmth at the 9 o'clock position on the left (the water here does seem to attain the expected fully "hot" temperature).
When I became aware of the issue, I mentioned it to the plumbing team leader, and he acted as though it was the first he had heard of the problem (though he has been extremely circumspect and terse in his communications with residents since his *second* week on the job) and would look into it. I then approached the plumbers who were at work in the hallway outside my suite, and one of them came in and felt the water, and, in all sincerity, informed me that all the suites were like this, and that it was due to what he called a "gap" (English was not his first language, so I'm not exactly sure what he was trying to say) at the back of the valve assembly that allowed a crossover or mixing of the hot water with the cold.
I then called Moen's customer service line, and described the situation and the plumber's comment, and the young woman said she had not heard of such an issue on a freshly-installed valve in her years of working there, and the fact that it was affecting all suites would suggest that it is a water pressure issue. She told me that this is a pressure-balancing shower-tub valve and requires equal pressure from both the hot and cold water, and that problems will arise if it is not. She advised that the water pressure should be tested to confirm that it is equal for both the hot and cold water.
I then spoke with the project manager for the plumbing work, and after he felt the water coming out of the faucet over the tub, told me in a dismissive and condesccending tone that if *that* was the worst thing I had to worry about, I was doing pretty good. He then walked out. (I didn't have even have a chance to tell him that his communication skills were being wasted in the plumbing business, and that he should consider a career in politics!)
I might also mention that the water in the kitchen is no longer as cold as it used to be (even after letting it run for 20 or more minutes), and I suspect that hot water may be mixing with the cold there as well, though the water there does at least get "cold" and not just "cool" as in the shower.
So, anyone have any kind of clear idea what is causing this problem and how it can be fixed? Should the plumbing company be paid in full for work with this outcome (and this is a job costing, for the two sister buildings involved, well into the seven-figure range), or be required to make whatever changes necessary to guarantee that, in all suites, only cold water water flows out of the tap when the faucet is in the "opening faucet" cold position? Was the project manager's attitude and behavior acceptable for a professional who can and must be held accountable for the work performed under his supervision?
Many thanks for your comments and responses!