Dear Plumbing Expert:

Our 6-year old house is on city water. About a month ago we noticed a strong H2S smell from one of the master bathroom sinks (second floor), when water was turned on. Further examination has shown that the smell comes only from the COLD water supply, and only when first turned on. Neither the hot water supply, nor the sink drain, has any smell. The cold water remains clear at all times.

The immediate rotten egg smell from the cold water goes away after about 10seconds of running. The smell returns only if the water is turned off for a period of about 30 minutes, and then turned back on. The relatively unused second sink had no smell until we started to use it more often. Now the cold water on that sink smells, but not as strong as the first sink.

The other upstairs bathroom sink (20 feet away) and the four downstairs sinks do not exhibit any abnormal smells or discolored water. Same for the upstairs baths, showers (3), and toilets(2).

Any ideas?

Plumber

Here are a few web sites that explain about Hydrogen Sulfide. Best I can determine is that a certain type of bacteria causes this.


http://www.cottonwoodwater.org/pdf%20files/Odor%20Questions.pdf

http://pureintake.com/hydrogen_sulfide_gas.asp

http://www.mikeswater.com/faq/hydrogen.htm

There is a chemical expert here , I hope he stops by and offers any advice he can, also a plumbing expert, he may help with how or where this bacteria can form and grow.

Hey Plumber,

Since the other fixtures aren't affected I would be more inclined to suspect bacteria rather then Hydrogen Sulfide. Try this, Shut the water off to the faucet and open it up. Pull the cartridge and soak it in bleach overnight along with the aerator if there is one. At then same time sponge the water out of the open faucet and fill it with bleach as well as forcing bleach up the spout. Next morning reassemble and sniff. Let me know, Tom

As a chemist, I may know the bacteria have to have a sulfur compound to start with to make H2S. As an AMHD Ultra Member, I know Tom has had more experience making H2S go away.

Thanks Tom (Speedball1): I took your suggestion, dis-assembled the cold water valve and soaked everything in bleech overnight. Next day, no more H2S smell in the cold water. Valve and spout were actually only 1-year old, but I guess that's long enough for sulfur-containing bacteria to grow.