Photograph of smelly dirty water running into a bathtub of a Poughkeepsie NY Home (C) Daniel Friedman Odors in Drinking Water, FAQs
Diagnostic questions & answers about odors in water

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Water odors & smell FAQs:

Here are common questions & answers about diagnosing & curing smells or odors in water or water piping systems, wells, tanks, or other water equipment.

This article series discusses how to identify, diagnose, and cure common odors that may be present in drinking water. We also discuss which of these odors may warn of unsanitary conditions.

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Questions & answers about diagnosing & removing odors in water

Question: dead rodent smell in municipal water supply

I have been searching the internet and haven't had any luck finding an answer to a question I have, so I hope that you can help. My family and I just returned from a 2 week stay at my mothers and when I turned on the cold water tap to brush my teeth I noticed a strong dead mouse (or rodent) smell coming from the cold water only. We live in a suburban area with town water which is filtered with a kinetico whole house filtration system with water softener.

I checked the water system and it seems to be working fine and no dead animals are to be seen in the salt container. My question is: is there a way for animals to get into the water line and die? seems kinda impossible, but I can't seem to figure out why our water would be smelling this way otherwise. Plus it maybe dangerous for our health if it is in fact a dead animal in our water supply. thank you for your help and I hope you can get back to me soon. - S.S. 1/5/2014

Reply: steps in tracking down a dead animal smell in drinking water

As the building is served by a community water supply, the chances of an animal inside the water supply are rather low or obscure; chances of a dead animal in your piping are also unlikely as one would expect a mouse or larger to block water flow - typically building water piping is 1/2 or 3/4" inside diameter, and an opening that would let an animal of any size in would also be a huge leak out - one likely to be observed. More likely there is a piping, water treatment or water pressure tank issue (if the building uses a pressure booster tank) - such as bacterial growth in the plumbing system.

Often "dead animal" smells are a sulphur like odor or "rotten egg" odor - ‚Äč WATER ODORS, CAUSE CURE should be helpful, as might
SULPHUR & SEWER GAS SMELL SOURCES where we list common sources of such odors.

If you indicated the odor were in hot water supply only I'd suspect an anode failure or bacteria in the hot water tank.

Indeed when a building is served by a private well, it is possible, depending on well construction, for an animal to enter and die therein; to be sure the water is safe to drink in such cases the occupants should discuss their observations and concerns with a water testing company and then have the water tested for potability.

Question: Halo water purifier - now rotten egg smells

(July 14, 2014) said:
We have installed a Halo water purifying system about 3 years ago and now have ongoing problems with a rotten egg smell coming from the hot water. First question, could this problem be caused by the Halo system? Second question, how do we solve this problem? The water heater is about 5 years old and we have replaced the rod twice. We live in a residential area in Torrance, California.



Indeed any water treatment equipment can flip into an odor generator if it becomes contaminated - e.g.with bacteria. Start by cleaning and sanitizing the equipment that you suspect.

Also double check that there is not a sulphur odor in the incoming cold water or a sulphur odor coming from the water heater.

See SULPHUR & SEWER GAS SMELL SOURCES - live link just above

Question: new carpets, weird chemical smell, blamed on toilets

(July 20, 2014) M.Bradley said:
We had new carpets put in all of upstairs and downstairs master/ and new tile in kids bathrooms upstairs in Mid May. ON 2nd day of this work- we noticed a weird chemical type of smell when we took showers down stairs, Work was completed on Day 3. Flooring company did come back until day 11 to replace toilets after flooring- and in that time they just blocked toilet vent with paper towel. We assumed odor was from toilets being off. Toilets were replaced but still smelled the chemical smell here and there. They came back and had someone else redo the wax seal etc.

Several weeks have gone by and still get that smell when showers are on- occasinally when running washer machine, or by toilets- but just occasional.( smell inensfies some if you use bleach etc in washer or clean toilets. We replaced gas water heater based on plumbing company thinking it was water heater/annodes ec. put a new tankless in. They said it may take a while for lines to clean out. Been 2 weeks. They came by and took a water sample from hose bib- trying to wait for that. House is 11 years old and only owner. I have read off- gassing of new carpet in rare circumstances have been associated with this when humidity from shower/ gassing odors in air? ,

Can you have a methane smell with out the rotten egg smell? This started when they busted the tile flooring upstairs bathroom, layed new hardy layer, then tiled. They had their commercial crew doing work because they were busy- I did noticed it seemed like they guys was being very aggressive busting out tiles for house bathhoom.

We had a leak company come out to do a smoke test- he had his guy look around the house- thought the main guy would be more hands on- he just smelled the water from the showers and said to maybe get water tested. None of my neighbors have this issue.

Reply: tips for more successful track-down of source of smells in a building or in water or plumbing systems


Your note is a good (but frustrating) example of the difficulty of tracking down odors and smells - we've tossed so many possibilities into the pot that it's as confusing as heck. Let's try to sort some things out and figure how to proceed:

Carpet off-gassing may produce a chemical smell but would be strongest in the rooms where the carpet and padding were installed and would not particularly relate to toilets, open drains, or water odors.

Sewer gases may smell like rotten eggs or sulphur as do some other odor sources such as LP or natural gas leaks or sulphur in a water supply.

Using an odor log or diary may help you sort out the complaint.


Also see this checklist

Odors in a hot water supply that smell like sulphur may be from a bad water heater anode, bacteria in the water tank, or water contaminants.

Odors in a cold water supply that smell like sulphur most likely come from well water high in sulphur.

Methane could be present from a gas leak: if your home has natural gas or LP gas fueled appliances that's something to check using soap solution or a gas detector and a detailed inspection.

Taking note of when and where odors appear, relating them to operation of equipment or fixtures or other events & equipment can help track down the smell.

Question: hard water with sulfur smell or water with rotten egg odors

(July 21, 2014) Anonymous said:
I have a well that had hard water in it before but within the last 5 has developed a sulfur smell in water. This was after using the well for 4 years. How could this suddenly happen? I shocked the well with bleach but the smell came back with 2 days. Now sure what to try now.

(June 8, 2015) rolando said:
our water smells like rotten eggs only the hot water cold water don't stink we have salt in what can I do to fix it myself

Sept 16, 2015) Anonymous said:
We have natural soft well water which has an oder to egg/sewer smell we change the filters monthly and also have a chlorinated system on the well which put pellet like tablets into the well when it works. most of the time we will open it an manually dump them in. the slimmy water after showering make you feel like you are not clean but after googling I guess that soft water is much cleaner then hard water. Being a women it makes my hair less managable unlike what is being advise as a positive to soft water. I would like to know if anyone out there is having this issue and what if any soluction is out there?

(Feb 16, 2016) Susan Lafer said:
My water has a sulfurous odor. My plumber can not find a reason for it and thinks I should replace the water heater.
Another plumber was out today and says it is caused by my water softener not doing its job.
He wants me to put in a Halo filtration system. I am totally at a loss as to how to proceed.


Water conditions can change in the ground or in water equipment, even a water heater. Changes in the aquifer, a drop in the water table for example, can change well water chemistry by sending different water sources into a well. Nearby mining or fracking or even well drilling or blasting can also have this effect.

Sulphur odors in wells are sometimes seasonal as water table level crops in dry season.

You probably will need to install a sulphur odor water treatment system.


Rolando in the COntinue REading links above see WATER ODOR DIAGNOSIS - SULPHUR

Susan: sulphur or rotten egg odors are often traced to a bad sacrificial anode in the water heater. If the water heater is in good condition I suggest replacing its sacrificial anode, then draining and refilling the device.

Question: rotten egg smell in very soft water

21 January 2015 Carol Gordey said:

We don't drink this water,use it for boiling on stove for cooking,has a h2s smell,like rotten egg,very soft water. We live on acreage,with well ,lots of gas wells and flare stacks, have 3 bathrooms,only one when flushed has that very bad smell.can this water and smell give problems with health issues



In the More Reading links just above see the article titled WATER ODOR DIAGNOSIS - SULPHUR for diagnostic and cure suggestions for the rotten egg smell you desribe.

Whether or not the rotten egg smell is also unhealthy depends on just what is causing the odor. Sulphur in water may be obnoxious but is not itself necessarily unhealthy, while in contrast, if odors are traced to sewage contamination that's obviously unhealthy.

Question: rotten egg smell in water at rebuilt home after a wildfire

(Mar 30, 2015) Randy said:
We just rebuilt our home from a wildfire. We are getting the rotten egg smell in the cold water. However this appears to only show up in 2 bathrooms that are located one directly above the other in the 2 story home. The smell only last a short period of time, maybe 30 seconds and then goes away. Which ever cold water is used first in the 2 sinks gets the smell and then not the other. If neither sink has been used for about an hour the smell will return and again for just the short period of time. Any ideas?



If you are sure that even after running the water for a time that the smell is only at two bathrooms and not at other plumbing fixtures and if the smell is definitely in the water supply, not coming from the drains, I would be looking for

1. a different water heater serving those areas, with a failed sacrificial anode

2. a bacterial contamiantion growth in a water tank or possibly even piping serving those areas

Some more obscure but possible odor sources could include heat damaged or post-fire remediation damage (such as over-use of an ozone generator) that affected plastic supply piping or chemical contaminants associated with the fire or with its extingishment and that entered the building piping or fixtures.


Dyer, Robert F., and Victor H. Esch. "Polyvinyl chloride toxicity in fires: hydrogen chloride toxicity in fire fighters." JAMA 235, no. 4 (1976): 393-397.

Strand, C. L. "One Hundred Years of Experience with Gas Systems and Fires Following Earthquakes." In Eight National Conference on Earthquake Engineering, April, pp. 18-22. 2006.

McQuillan, R. G., and P. G. Spenst. "The addition of chemicals to apartment water supplies." Journal (American Water Works Association) (1976): 415-419.

Whelton, Andrew James, LaKia McMillan, Matthew Connell, Keven M. Kelley, Jeffrey P. Gill, Kevin D. White, Rahul Gupta, Rajarshi Dey, and Caroline Novy. "Residential Tap Water Contamination Following the Freedom Industries Chemical Spill: Perceptions, Water Quality, and Health Impacts." Environmental science & technology (2014).

BELLONI, K., T. PALOPOSKI, K. SAARELA, K. TILLANDER, and K. VILLBERG. "Tulipalon Jalkihajujen Poisto (Removal of Fire Odor)." (2007).

Reader follow-up:

(Mar 30, 2015) Randy said:
Dan, appreciate your quick response. To try and narrow this down further here are some facts. The fire destroyed the entire house and nothing inside the home could be salvaged. The smell is definitely in those 2 sinks only and again only on the cold water supply.

If it were the drain would you not have the smell when either the hot or cold was turned on? The one hot water heater we have is a Triangular Tube Smart 50 indirect fire that has stainless steel tubes and therefore no sacrificial anode. If there was bacterial growth in the holding tank wouldn't again the smell show up in more than these 2 areas? If after review of these facts does it appear that there may be a bacterial growth in piping serving those areas? If you think so how would I approach the problem for a solution?


Yes certainly if there were a bacteria problem in the tank it ought to show up at all hot water fixtures.

There are some instances of bacterial growth or biofilms in segments of piping - but it'd be odd to show up in some and not others, and if the fault were the piping I"d think it would diminish after you've run water for a while.

It's possible to sanitize a piping run using appropriate isolating plumbing fittings that allow you to circulate water with a cleaner or disinfectant through just a segment of piping. A plumber needs to add the needed taps and controls and then use a pony pump and container and an appropriate cleaner.

But it might make sense to think a little further about what's going on before doing anything.

1. You say the fire destroyed everything: literally? Are we talking about an entirely new structure perhaps simply sitting on an old foundation? 100% of mechanicals, pipes, fixtures all replaced? If so I'm puzzled about how this might relate to the fire itself.

2. does a smell test leave you sure it's hot water coming out of a couple of fixtures, not the fixture itself for example?

3. have you asked a local lab if they could accept a sample for testing?

Randy I've traced odors blamed on a kitchen sink to sewer gases leaking out of dry floor drains in a basement below. Check that source too.

Reader follow-up:

The fire literally destroyed the entire structure including the foundation. The only reason this was brought up was because you had mentioned some possibility of other damages from the fire. The water has been tested 3 times with no problems. I'm still not sure you understand where the smell is coming from. It is only in the cold water side of the 2 sinks and yes as I said before the smell goes away after about running the cold water for about 30 seconds.

Depending on which sink the water is run in first it does not show up in the other at all. Probably 90% of the piping is the blue and red plastic piping. You mentioned whether it could be the fixture itself. I have stepped away with a sample of the water and there is no smell. I'm not sure how you would tell if it was the fixture and not the piping. If it was the fixture where would be the problem? Would it show up in both the hot and cold water? Remember again I am only detecting this smell on the cold water side.


Got it: sulphur/rotten egg smell in cold water, not in hot, and in the water but oddly only at some fixtures, goes away after running water for 30 seconds.

That is suggestive of an odor coming from water having sat in the pipes enroute to those fixtures. Indeed it's impossible to make a thorough diagnosis of many problems by e-text. In my experience, almost always when an experienced diagnostician goes on-site s/he observes important evidence that simply was not apparent to someone less familiar with the issues.

About the best we can do remotely is think aloud and ask some questions.

Ask with care: what's different about where and when the smell appears from elsewhere in the home. Longer pipe runs, pipes exposed to heat, or piping that's contaminated are hypotheses that occur if we are simply guided by your own observations.

Having "tested" water is unclear since depneding on how a water was sampled, how quickly the sample was got to the lab, how sterile was the container, and what the lab tested-for are obviously important variables.

At SULPHUR & SEWER GAS SMELL SOURCES we list common sources of smells described as "rotten egg": typically the root cause is sulphur in a water supply (which should show up at all fixtures and that often will diminish when water is run for a time), bacteria, or contaminants from dezincification of brass fittings on PEX type piping.

As you have "red and blue" pipes I am guessing you've got PEX. It might be worth looknig very closely at every fitting for evidence of dezincification.


Reader follow-up:

(Mar 31, 2015) Randy said:
I appreciate all of your input. I will go through the thought process as you mentioned. Unfortunately I won't be able to get to most of the PEX for inspection of dezincification.


Of course Randy - it's too darn easy to give advice that is infeasible.

Take a look at the dezinc article and you'll see that the faster corrosion is on hot water piping that is also acidic (low pH) and /or contains higher levels of chlorine.

Check the accessible connectors as samples. Unless you find evidence of trouble or see leak stains elsewhere I doubt it's cost-justified to start ripping open walls or ceilings just to look.

Question: acetone odor in water?

(Oct 17, 2014) KAREN VAN ESSA said:
For the first time in 10 years I can smell acetone intermittently in my cold water, which comes from a drilled well 130 feet deep. I have had the water tested for a broad range of chemicals at least twice before: levels were below all guidelines, except for sulphur and hardness, but the levels are tolerable and I have no water softener.

There has been no construction in my rural neighbourhood, the nearest house is 500 feet away, and the only industrial site is a car wreckers/body shop about 1/2 a mile away whose owner is semi-retired.The land has not been farmed for at least 25 years. What could be the source of this volatile? Could it be natural? Is it dangerous? (this is a mainly wooded area with small streams and ponds) (PS Sorry, initially posted in wrong section)


try the diagnostic suggestions at WATER SMELLS or ODORS, OTHER as well as another water test

Question: remedy for bacterial growth or biofilms in piping

(Apr 5, 2015) Anonymous said:
If i do have bacterial growth or biofilms in segments of piping, how do i resolve the problem without an expensive plumber?


Anon I'm not sure you can unless you are able to handle the necessary plumbing tasks to install fittings to permit pumping a cleaner / sanitizer through the piping system. Add the costs of the pump and connecting hoses and containers.

Question: garlic odor in bottled drinking water?

(May 20, 2015) Anonymous said:
what causes onion/garlic odour in bttled drinking water



This is not a particular odour complaint I've come across. There could be an effect of the plastic or the water itself. Did you ask the bottled water company about the matter?

Question: strong odor and yucky water taste

(June 2, 2015) said:
We have about 100 units at a summer only park. We had 8 units that were winterized by the same plumber. On de-winterizing the water has a strong odor and tastes yucky. It has been almost a month and not a lot of progress on the smell and taste. The water company has tested the water, and it tested fine. The other units that used a different plumber are not having the issue. The plumber says it is the water company (then everyone would have the same issue).

He says there is no way to fix. What do we do to get the anti-freeze out of the water.


First test your water to confirm that it has the chemical contaminant that you suspect; then flush the system.

Question: water smells like rotten oranges

(Sept 14, 2015) Anonymous said:
My water smells like rotten oranges



Rotten oranges is not a water odor complaint that we've come across before, but then people's sensitivity to odors varies widely as do odor perception and description.

Confirm that others smell the same rotten orange odor. There are medical or neurological conditions (parosmia ) that can cause mis-perception of odors.

There are some molds that can produce a "sweaty sock" or "dirty sock" odor that some readers have described as "rotten oranges"

Look for discoloration in the water; an orange hue may be due to high iron content or rusty pipes; there are also iron-loving bacteria that could be at work.

Question: water smells like rubber

(Oct 1, 2015) Anonymous said:
What makes well water smell like rubber


Check for old rubber tubing or hoses anywhere in the water supply;

Question: painted cistern with swimmign pool paint - left paint odor in water

(Feb 7, 2016) Geoff said:
I have just had my concrete water cistern painted with swimming pool paint but the wtaer now has a strong paint odor. What is recommended to clear this? I have thought of adding chlorine (the water is not used for drinking).



Watch out: I'm concerned that your water may not be safe to drink - there may be chemical contaminants in the pool paint that make it not suitable for use in a cistern. YOu say the water is not for drinking but don't indicate what it IS used for. Start by calling the paint manufacturer to discuss your concern - be careful not to sound threatening or you'll get nowhere.

Get the MSDS for the paint that was used and read it with care.

Question: gasoline odor in water

(Mar 15, 2016) Anonymous said:

I always put my drinking water in a water bottle so that i can monitor how much water i drink everyday. No problem at all for many years. Recently i noticed there's gasoline smell in my water, after my son complaining about his water bottle stinks. At first i thought may be i didn't wash his bottle clean enough, so i wash it more frequently, but the smell keeps coming back. So i gave him a new bottle thinking that may be it's the bottle that is too old. But no, the same stinky smell again.
And than it's my turn. I have changed to a glass bottle but no help.

Now is my mother inlaw's turn, same thing happen. But not my other family members.
There are 7 of us under one roof. Water is from the tap but filtered. We always boiled the water.
Please advise. Thank you.



I suggest taking a test sample of your water to a local water test lab, describe your concern, and ask what tests they recommend. In fact discuss the test with the lab first, as special water sample collection steps might be required.

Watch out: gasoline has been known to leak into nearby water wells from leaky gasoline storage tanks; if your home is near a gas station that could be a problem source.

Question: water smells bad, like something has died

(Mar 28, 2016) Alan said:
We have a borehole and also utilise municipal water. We recently installed a 3 phase outdoor filtration system but now some 3 months later the water smells really bad like something has died in the tank or geyser. Its more noticeable from the hot tap but we are now noticing it in the drinking water that we bottle. I took a sample directly from the borehole and it's fine (also had it tested and its excellent quality). I also tested directly from the water tank where we have borehole and municipal water and its also fine. Is there anything in the filtration system that can cause this?



I don't know what's in the filtration system, what maintenance it required, nor what is its susceptability to bacterial growth or other contaminants. You might want to review that. For example, often a filtration system needs to be combined with chlorination or other disinfection.

Bacterial, algal, or other growths in filter media can be the problem.

Sulphur and other contaminants can also smell like a dead animal - as can a dead animal itself.


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