I found this forum recently while educating myself prior to getting a new water softening system. I found a lot of really useful information. I haven't had the new softener installed but have run into a baffling problem with a new carbon tank system.

I just had a whole house carbon tank system installed last night. 4 cu.ft of GAC in a tank with a Fleck 7000XTR valve (all new equipment). I am on muni water in Orange County, CA. I've NEVER had any odor issues with my water before other than the typical chlorine smell of municipal water. House is 11 years old, 4.5 baths, master jacuzzi tub with 15 GPM flow rate, etc. I wanted the carbon tank to get rid of the pervasive chlorine smell (water district uses chloramines). (I have hard water, tested between 15-26 GPG hardness and TDS of 467.) I previously had a national brand combination of carbon and softening resin in a single tank--I never had problems with odor.

The new carbon tank was backwashed twice and then placed into service. The water in the house now has a really strong sulphur/rotten egg smell. The chlorine smell is gone but the sulphur/egg smell is nasty. The odor is definitely not coming from the drain--I filled cups with water and smelled them like glasses of wine. It's the water.

I didn't smell it as much on the hot line. It's really strong on the cold line. I tested it at multiple taps. I ran the water for a really long time to flush the lines. It didn't go away over night. I grabbed a few cups of water from a bib prior to the tank system and there was no such odor coming from the muni supply.

Today, I bypassed the carbon tank. I ran the cold lines to flush them. The sulphur/egg smell went away and the cold water now smells like chlorine again.

The installer says that he's never heard of a carbon system causing odor and he says it cannot be the cause. Based on the fact that I've never had this odor before, it appeared immediately after placing the carbon tank online, and it disappeared when I bypassed the carbon tank, it looks to me that the carbon tank is involved somehow.

The only other change was that I did my annual hot water heater draining yesterday (gas water heater) before placing the carbon tank online. But as noted above, I'm getting the strongest smells on the cold water lines (including dedicated/non mixer cold lines) and the smell dissipated on the cold line when I bypassed the carbon tank today.

I tried to do some research and only found articles about getting rid of such smells in the water supply, like hydrogen sulfide in well water. I found nothing about my situation.

Does anybody have an idea about what's going on here?