I've read all the posts about smelly cold water (great work, BTW!), but nothing quite matched the symptoms we're experiencing:

We moved into a 2-year old condo last year and immediately we noticed the master bath toilet wouldn't completely flush, unless we held the handle down until it completed. Shortly after moving in, my wife complained that the water coming out of her bathroom sink smelled like a sewer. My sink water didn't seem to smell at first, but now it does. The water only smells when initially turned on (hot or cold) and then it goes away if left running. There is a recirculating pump under my sink, which can be set to run during certain times of the day or be set to run all day. I recently set it to run all day and I believe my sink water smells more often now. No other sinks (2 other bathrooms and the kitchen) in the condo smell -- just the master bath sinks. I mentioned the toilet flushing problem, because I know that drains must be vented to the roof for water to drain properly. Is it possible that the drain air vent is clogged and that it's preventing the toilet from flushing well AND that the trapped gas is somehow being sucked into the water line by the recirculating pump? The roof is steeply pitched and two stories up, so I would need to call someone out to check the vent. I'm just looking for validation that this might be the culprit, or if there could be another cause for these problems.

Hi Doug,

The "lazy flush" in the MB could caused by a number of things besides a cloged vent. The flapper linkage, the tanks water level, a partially clogged jet or drain line, the bowls fill tube could be blocked to name a few.
You ask,"Is it possible that the drain air vent is clogged and that it's preventing the toilet from flushing well AND that the trapped gas is somehow being sucked into the water line by the recirculating pump?"
If it's one mandate that all plumbers observe it's to insure that AT NO TIME SHALL DRAINAGE AND POTABLE WATER COMMINGLE OR CROSSCONNECT.
The two systems are isolated from one another. This is the prime directive in plumbing.
Since you're in a condo the water source for your unit is shared by all units in the building. Have there been other complaints? Have you checked with the condo board? If there have been no complaints from the other owners then the problem's contained in your unit.
Smells, intermittent noises and bad tates are the hardest for a plumber to track down but if this were my call I'd began to suppect bacteria growth in the supplies or the faucet cartridges. First I would pull the faucet cartridges in the smelly lavatories and soak them in bleach. Next I would pour bleach into the open valve bodies and flush them out. If that didn't get it I would back flush the supplies and recirculating line with chorine or bleach. But I would "nip it in the bud" before it spread to the rest of the system.
Good luck, Tom

Hi Tom,

Your explanation of the drain lines vs. potable water lines never connecting makes sense, so I'm abandoning the idea that the toilet flushing and tap water smell problems are related. I haven't asked other building residents if they have smelly water, but because our other sinks don't smell, I have to assume the source is near the master bath. I've turned off the recirc pump (it's a cold water recirculating system), and that seems to have abated the smell, but I need more time to make sure. If it comes back, I'll try the disinfecting procedure you described. It's funny you mentioned that in addition to smelly water, intermittent noises are also difficult to diagnose. I forgot to note that there is a rhythmic tapping noise under one of the master sinks (not the one with the recirc pump) when the hot water is running, but it doesn't happen all the time! Again, it may be the recirc pump, but I'm having a hard time figuring out why. Your reply has helped a great deal and if you think of anything else, I'd love to hear it. Thanks!

Doug

Cold water recirculating pump?. What would be the point?. I could see maybe in the kitchen drinking water, I guess to keep it as cold as possible but in the bathroom? Uh... it could also be a bacteria growth growing right under the pop-up, I've seen instances where someone has used plumber putty that has started to mold, And smells very bad but after you run the water it goes away for a few hours,. but speedballs cartridge explanation makes more sense.. don't know what the pump would do with it...

The pump is there to keep hot water on tap, but it does so by circulating water back through the cold water line to the water heater. This is what I meant by a "cold water recirculating" system, but I should have said it's a "cold return" system. My mistake. It seems as though you are right that the pump has nothing to do with the problem, because the water still smells, even with the pump off.

I am experiencing the smell water problem in my 2 face basin. Its an awful scent toce because I sometimes forget it exits. I have just moved into my new home in December 2010 and I started smelling the stench round abou thte middle of January. I reported to the plumber anf was told the scent will go away, it has something to do with the thing used to stick pipes etc... This is may and I am still suffering...

Almost all water supplies contain sulfates in the water. Unless the water supply is being chlorinated bacteria can be introduced into the system (simply from bacteria on your hands) and react with the sulfates in the water. This creates sulfate reducing bacteria and can create a rotten egg or sewer type smell in the water supply. Also the anode rod in a water heater will degrade and cause a similar odor in the cold water supply. If you have a water softener the softened water will cause the anode rod to degrade faster. I have seen many times where the odor is only occurring at a bathroom sink. The way to treat this is to chlorinate the plumbing system. If you have a pre-filter housing at softener, simply fill with household bleach (by-pass softener) and run water at furthest point in home until bleach comes through. Then open all cold water faucets in home until bleach is drawn to each faucet. Shut off water and let sit for several hours,flush system completely of bleach afterwords. Put softener back in service, flush water heater from bottom drain on heater. DO NOT shut water off to WH while flushing, flush for 5 minutes, let sit and repeat.
If you do not have a pre-filter one can be installed relatively easy at water supply point of entry.
RJ