Dirty water smell on dishes

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crisgraham

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Location
Eden Prairie, Minnesota
We have a “dirty water” smell around out kitchen sink on the main floor. In addition, our dishes come out of the dishwasher smelling the same way. The smell is very strong, intermittent, and seemingly much more noticeable when we have our windows open than when they are closed with the air conditioning on. Though less prominent, we have the same smell from our bathroom sinks upstairs. I describe it as a dirty water smell as opposed to a raw sewage smell.

We have done the following:
1. replaced the dishwasher
2. tried different dishwasher detergents
3. replaced the disposal
4. rerouted the drain hose from the dishwasher
5. inspected the backflow valve on the dishwasher
6. used disposal cleaners

We suspect it might be the vent system. The house was built around 1990, so the plumbing is fairly modern. There is an upstairs bathroom right over the kitchen, so we filled the tub with water and drained it along with flushing the toilets and running the sinks all at the same time, but we did not detect any gurgling in the kitchen drain. About 5-10 years ago I noticed that the single vent pipe had a rubber cap on it so I climbed up on the roof and removed it. I didn’t notice any immediate difference.

One plumber thought it might be the hot water heater, so he drew off some water from the heater, but it didn’t smell. It did have a lot of sediment in it which he flushed out. We have not replaced the hot water heater which is the original one.

While there is a single vent pipe coming out of the roof, it serves 3 ½ bathrooms, plus the laundry and kitchen. We do not tend to notice this smell on our clothes coming out of the washer or from the other two bathrooms. There may be some connection to the one bathroom being above the kitchen.

I’ve been told that running a scope down the vent pipe won’t get off into the branches. I’ve also been warned about running a hose down the vent to try clearing out any blockage.

I don’t know what to do. I can’t find a plumber who knows either. My first question is: what is the likely cause? My second question is: how do I verify that is the cause?
 
This has me stumped as well. Are your drains flowing quickly, or are they sluggish? Are you on city water, or do you pump from a well? Have you tried increasing the temperature on your water heater to see if this makes a difference? Is this home used daily, or is it possibly a vacation home with little usage? Have you removed the screens from the faucets and checked for sediment or algae? If on city water, have you contacted the water department to determine if your water source is functioning properly? I asked this last question because in my area, we recently received a notice of foul smelling water as a result of algae in the reservoir.

I hope others can chime in for their opinions as well.
 
Thanks for the quick reply.
1. The drains are not sluggish
2. We are on city water
3. We did turn the water temp up
4. It is our main home and occupied all the time
5. We have removed the faucet screens and checked for sediment
6. We did not check with the city as the water itself does not smell and we don't get the odor from all sinks.

Do you think this is possible: when the house is closed with the central air on, there is pressure in the house from the pumped in air and then when we open the windows, we release the pressuere and the smell comes in thru the drains, suggesting that it's possibly a vent problem? We get the smell under both circumstances, but much more frequently with the windows open. Would this effect the way the dishes smell?
 
With central air, air is sucked in from the house, gets chilled, and returned back into the house, therefore, you should not have a substantial change of pressure. You may have dried up P traps which would allow sewer gasses to enter the home, but would not cause smelly dishes unless your air gap on your dishwasher was not functioning correctly. Seldom used stagnant pipes could be the root of your problems, but if the house is occupied, would not be the problem.

Did this smell begin recently? I'm afraid that other than going from drain to drain with your nose close by, and attempting to pin point this problem better, or just having a plumber snake and/or inspect your pipes with a camera (looking for cracks in the vent lines), I'm out of ideas.

There are some great plumbers who will pop in shortly and give you their expert opinions soon.
 
Good point about the air conditioning.

The dishwasher is used every day. We've had the smell for over a year (which is why we're tried so many things). And, it seems to be concentrated in the kitchen (sink and dishwasher) and the upstairs bathroom.

I was thinking of replacing the hot water heater since it's 20 year old and probably needs it anyway. Any chance that might be a cause? I was thinking not since our clothes don't smell, but we tend to rinse them in cold water - and we haven't noticed this smell in other areas of the house.

I'm open to any and all suggestions!

Thanks
 
I don't think it will solve your problem but a 20 year old water heater is certainly on its last legs. I would recommend looking into tankless water heaters. With all the rebates these days, it makes it worth while. I'm also doing my own research and so far, since I installed my TWH, my gas bill has been reduced about 38%, and for the last 9 months, I have saved $90 on just my natural gas bill.

The first thing I would do is contact your water department. Have them come over to analyze your water to rule out your water supply. It just may be that you are on a leg of the water supply that has internal problems. Once this is ruled out, move onto your waste and venting.
 
We ran into the same thing about three years ago. We had a costumer that had the same complaint you have.
There old well had a hole in the casing and needed a new well.
After about two months they had a smell coming from the dish washer and sink.
Since it was a new well, it was thought to be be the cause, but it was nowhere else in the house.
After having the water tested,it came back fine.
We went into the house to have a look. It turned out the smell was coming from the washer, but it was not the water causing the smell.
In the back bottom of a dish washer there is a screen, under that is a very fine screen. The fine screen was covered in food stuff that did not wash down, and that had been there long enough to start to rot.
That rotting food was the source of the smell. It was cleaned out and the smell went away.

I'm not say that this is your smell problem, but it may be something to look for.

Travis
 
Travis has a good idea. Pull your air gap to the dishwasher (backflow valve) and smell both sides of it. If the smell is coming from the dishwasher side, Travis is probably correct. If the smell is coming was the garbage disposal side, it could be within the sink itself.
 

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