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The sink is pretty close to the toilet...about 2 feet away. I've noticed that often times when I turn on the faucet (either hot or cold), I smell a sewer kind of smell.

What could be causing it? I thought traps were suppose to prevent this exact thing.

milesmeow
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    Do you get the smell with either the hot or cold water, or just the hot water? If it's just the hot water then it means the sacrificial anode in your hot water heater is due to be replaced. – bigbull15 Jun 21 '16 at 05:02
  • If it's not the water, then it could be some foul gunk in the trap... pour a little bleach (like one ounce) into the sink (trap) and see if it helps. – Ben Welborn Jun 21 '16 at 14:08
  • It happens with hot or cold. I will try the bleach trick. :) – milesmeow Jun 21 '16 at 16:04
  • What if you fill a glass with water... does the water smell bad or is the smell comming from the sink drain? – Ben Welborn Jun 21 '16 at 16:39
  • A filled glass of water does not smell bad. – milesmeow Jun 21 '16 at 17:01
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    Ok, so it's the drain. Quick test: plug the drain and fill the sink with water. Release the plug. You might see a bubble or two at first, but if it keeps bubbling as the water is draining then you probably do have a clogged vent pipe. If not (ie., the water just goes down without throwing up an equal volume of bubbles), then you probably just have to treat the p-trap with some bleach. If you have a shallow sink (not much water or time to observe bubbling), you should fill a bucket of water and pour it into the sink, slowly, as the sink is draining, so that you can see if the drain is bubbling. – Ben Welborn Jun 21 '16 at 20:23
  • I performed the test by filling the sink with water and then releasing the plug. (Note that I don't have a rubber plug that I can pull up and completely remove. I plug and unplug by pushing and pulling down/up a metal rod). I didn't observe any bubbles at all. (Note that the gap between the plug and the drain is not a lot...probably only a couple of millimeters...don't know if this affects the test or not) – milesmeow Jun 22 '16 at 05:58

2 Answers2

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I think what you've got is a blocked vent pipe, or worse, a non-existant or improperly-installed vent pipe. The vent pipe is supposed to connect to from the waste pipe stack or top of a lavatory drain pipe up through the roof, and is there to equalize plumbing system pressure and provide a means for sewer gas to escape. If the vent pipe is blocked, then the water flowing from the sink will increase the air pressure in the waste pipes, possible forcing sewer gas through the toilet trap out into the bathroom.

Check your vent pipes to make sure they're clear and hooked up properly. The article here might be useful http://bradyinspects.com/plumbing-vents

AndyW
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  • I think that this is a prognostication without enough evidence... though you may be correct, it has not yet been ascertained whether the smell is comming from the fresh water or from the drain. – Ben Welborn Jun 21 '16 at 16:43
  • True enough. My answer is a possibility, not a certainty. Let's see if we get further clues from Miles to narrow the scope... – AndyW Jun 21 '16 at 16:50
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I am assuming this is a new issue on an old drain; it could be as simple as the sink drain itself is partially clogged. Try running a cable down and clearing the drain out.

I am not sure that I understand the physics perfectly but have personally experienced this on more than one occasion. The partially clogged drain affects proper drain function and the water seal in the trap is compromised by a siphon action.

Jimmy Fix-it
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