We had a new shop built and had a new hot water heater installed on our well. Some of the sinks were smelling like sulfur so we did a half of quart of bleach and ran the lines and let it sit etc. We still have one sink that smells like sulfur, hot or cold water, doesn't matter. Why does this one still smell? You can run it for 30 seconds and all is good. The end of the sink strainer is clean, no idea why only this one smells and the others don't. Any ideas?

Iron sulfide in the well water will smell like that when it's heated. Get something to take the iron sulfide out before the water heater

Our well has 17ppm of iron in the water. That doesn't sound like a lot but we had to install a food quality hydrogen peroxide injector and filter system to get rid of the smell. $5500 later the smell is gone.

Sounds like the drain. Run some water in a cup, and don't let it hit the drain. If the water smells, it is the water, if not, it is the drain. If it is in fact the drain, pour two cups of bleach in it and let it set for two hours, then pour a few cups behind it and let it sit a few hours before flushing out. If it is in fact the water, you will need to treat the water.

What brand of heater? Some have magnesium anode rods that make the issue worse. They make an aftermarket anode for smelly water applications.

https://www.health.state.mn.us/communities/environment/water/wells/waterquality/hydrosulfide.html

Wasn't the drain, I wish it was that would of been an easy fix

Not a new well, just hot water heater, if that makes a difference.

Not sure of the brand, but it does have an anode rod.
The question is why after doing the first round of bleach that it cleared up all the other sinks, but not this one.
Wouldn't it still smell in all the other faucets etc.?