We have a 150 ft. well. About 6 months ago we noticed a very offensive odor from every cold water tap in our house. We delivered a sample of the water to a teasting lab and it passed with flying colors.

A couple of weeks ago we had a well specialist open the well and he let the water run for about 1 1/2 hours. The first water out of the well was reddish orange, then turning to milky and then clear. The specialist said the reddish orange color was iron ( we have a water softener that removes iron) and the murky water was normal as the well is in sedimentary rock. He cupped the water several times and smelled and tasted it. He said it tasted good and there was absolutely no odour. He said the smell was not coming from the well. He did not put any bleach in the well .He advised us to drain the hot water tank ( anode has already been removed) a couple of times and run all the cold water taps in the house, which we did.

We enjoyed 2 days of fresh smelling water and then the odour came back.with a vengeance. The well specialist has now recommended a chlorination of all the water pipes ( copper) within the house. He would leave the bleach in the lines for 24 hrs.

What are the chances of this working? Do we have any other options?

Since the plumber eliminated the well that leaves me to think you've picked up some nasty bacteria in your system.

The well specialist has now recommended a chlorination of all the water pipes ( copper) within the house. He would leave the bleach in the lines for 24 hrs.
That's what I'd try next, Good luck and let me know how you make out. Tom