My vote is for sulfate reducing bacteria that colonized a length of CPVC pipe. Coliform is possible, but in a 100 ft deep well?
It doesn't matter what type of reducing bacteria caused the odor because all are harmless. Coliform indicates the probably of harmful bacteria.
The depth of the well has next to nothing to do with bacteria contamination but 100' isn't a very deep well, it's actually fairly shallow. My record is a few months old 605' well that had Coliform in it and was found only after the family moved in to their new house and their month old infant was very sick and the doctor mentioned testing their water again.
Bacteria live anywhere in the earth that is not too hot for them to survive and then, as we see with black smoker vents on the bottom of the oceans, with water temps to as high as IIRC, many hundreds of degrees F, some types of bacteria thrive there anyway.
The odor you smell is from the digestive gas the bacteria produce, not the type of tubing/pipe that is used. The gas is dissolved into the water and as soon as you open a faucet the water is depressurized and aerated causing the release of the gas into the air and you smell it.
I was able to isolate the smelly issue to a length of CPVC pipe. There was no smell in PVC or copper runs from the same well. Not concrete proof of anything, but suggestive enough to me along with the driller's anecdotes that I want to avoid CPVC.
See above but, bacteria can grow and create colonies anywhere in the water system. Including in copper or SS tubing.
You say UV is no good with sulfate reducing bacteria? Can you please explain interaction of UV and H2S ? Since we can't smell anything, I assume we don't have any bacteria now.
You should not assume no Coliform because you usually can't smell and you can never taste it.
All the things I listed previously, and especially reducing types of bacteria, cause a coating on the outside of the UV light's (clear like glass pipe) quartz sleeve that the lamp is inside of and the coating blocks the transmission of the invisible UV light from penetrating it so the light can't get into/through the water inside the UV chamber. You may as well unplug the light 'cuz all you're doing is wasting electric and feeling good thinking the light is working but there is no 'deactivation' of the bacteria in the water.
Reducing types lay down a slime on the quartz sleeve, H2S gas, hardness, iron etc. causes a sediment to form on the quartz which prevents the light from getting through. Which reduces the time between scheduled maintenance and thereby increases maintenance of the light. As little as a fingerprint on the lamp or the quartz blocks transmission also.
The info I want to obtain is whether PVC can be used from the pressure tank to the UV and pass inspection.
So far I sense a "maybe, maybe not".
My opinion, which is not worth 2 cents in this field, is that PVC is perfectly adequate for this purpose. You are right, my pressure is never more than 60 psi and the temperature under the house is rarely above 80, so the pipe should work just fine. But I want to pass the plumbing final inspection, so I have to do things with that in mind.
My wife has informed me she was witness to the HD "Master Plumber" telling me to go ahead and use PVC up to the UV. And I did. And now I wonder if I need to rip out what I've done
I agree and as far as I can see, if you are having the installation inspected, you need to get the local inspector's interpretation of the code there.
But, it is still a free country and millions of feet of PVC is in use outdoors in sunlight on well and irrigation systems unprotected from sunlight or the UV light in sunlight. Plus you are not 'distributing' your water until after the water treatment equipment. You are also not inside the foundation or inside the house.
If it was mine, I'd use 1" sch 40 PVC. I have also used it on UV lights with a flow control button in the inlet, for over 20 years with no known problems and my name and phone number is on every one of them so I think I'd hear if there was a problem with a flooded basement etc.. But I am not telling you what to do other than to talk to the local inspector if you are having an inspection.
BTW, that 75 psi PRV I mentioned is code everywhere but many people don't install one because if it pops, they are usually not plumbed to get rid of all that water from flooding the place. And in 14 years on the internet and 23 years in water treatment and pump and pressure tanks, I've never heard of one having popped yet.