A Quick Guide To What an Odour In Your Water Might Mean

Cathal Walsh
Environmental Blogger
Wednesday, 27th March 2019
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Asian woman standing against a wall ,smelling a cup while grasping her hair lightly with the other hand

Odour in water:

An odour coming from your drinking water at home is a common problem; the types of the odour can vary from severe to benign based on what causes them. Luckily enough it is sometimes possible to distinguish the cause of the odour based on what you smell. This is a quick guide in identifying the potential cause of your odour based on what you smell.

CAVEAT: This is not a definitive indicator and should not be relied upon, for safety reasons and for a definitive answer be sure to test your water if you notice any sort of smell coming from it.

Sulfur /rotten eggs odour:

If your water smells like rotten eggs take this as the presence of sulfur. The odor is usually caused by the presence of sulfur bacteria or hydrogen sulfide  gas in the water supply.

The good news about these compounds is that the odour and taste are so unpleasant  at low levels of contamination that they prevent most people from drinking the water before the contamination reaches higher levels.

There are three possible ways to get sulfur and the smell of it out of drinking water:

Chlorination of Chlorine injection:

Chlorine will react with the sulfur and neutralise it to form a tasteless odourless yellow particle


Oxygen will react with the hydrogen sulfide  to form an odourless dissolved version of the sulfur called sulfate.

A dirty/earthy odour :

This is sometimes also referred to as a musty odour. You may notice this smell the most when turning on and off your hot tap. This is most likely due to elevated levels of Iron in your water supply.  You may also notice a build-up of slime in your toilet tank or in other fixtures.  When iron mixes with the oxygen in the air they form iron bacteria. Due to the fact that it is a bacterium, places like a boiler and other warm places in your house are the perfect conditions for iron bacteria to form.

It gives off the earthy or musty odour when the bacteria die. Though this bacterium has not been shown to be harmful to humans, it gives off a very distinct and unpleasant smell and taste and will make your drinking and bathing water a whole lot less appealing. For this reason it is quite a nuisance and should be dealt with in a timely manner.

Using a chlorination system in conjunction with a water holding tank will effectively reduce the bacteria level and help oxidize the iron so this problem would be sorted quite fast.

Fishy smelling odour:

A fishy smell indicates that naturally occurring organic material has made its way into your water at some point along the line. This smell indicates the presences of elevated levels of chloramines, barium, or cadmium.

Chloramines are a compound of chlorine and ammonia and are used to disinfect public water. Barium and cadmium are naturally occurring metals found in natural deposits that can make their way into your water as a result of fertilizer contamination or deteriorating pipes and plumbing. Though this smell may be unpleasant, the contaminants most likely to cause this smell are very unlikely to pose a threat to health.

The only way in which contaminants like this may be removed from water is through either a filtration system like a set of carbon filters, or through a reverse osmosis process. The water after either of these would be free from contaminants and odour free.

Swimming pool water odour

This is sometimes described as a smell of bleach coming from the water or the smell that one would get if they smelled a sample of water from a swimming pool. This smell is mainly complained of by homeowners who get their water through a mains water system in the city. In addition to this, those with homes located closer to the city’s water treatment plant complain of this smell more.

This is due to a presence of chlorine in the water. Although chlorine is the same chemical that was weaponized in gaseous form in the First World War, one should not worry about the presence of it in your drinking water. The purpose of adding chlorine to the water is to disinfect it and make the water safer for human consumption.

If you have an excess amount of chlorine in your water, do not fear. It does not pose a health risk for consumption, only acting as a mild irritant to skin and giving an odd smell and taste to the water.

This however is good enough reason to rid your water of the excess chlorine however. Chlorine can be easily removed from water by using either a system of filter in your water delivery system or implementing a process of reverse osmosis in the same.

Petrol/ Oil odour

If you smell an odour of petrol or oil coming from your water then it may be one of two things.  The first one is the presence of Iron in your water.

This may cause a red stain to any surface that your water may be touching, including skin or hair, but is common in groundwater and is for the most part completely harmless.

The second cause is a lot more sinister. The smell of petrol or oil may be as a result of a fuel leak getting into your water at some point during its journey from the source to your tap. Fuel can easily penetrate plastic pipes and make its way into a water supply, even if a source of spilled fuel comes into mild contact with a pipe.

If this is the cause, refrain from consuming the water and contact your water service provider immediately. Ingesting the compounds in fuel or oil can do untold damage to internal organs and can be highly carcinogenic.

It’s best not to take the chance of assuming a smell of fuel from your water is benign. If you smell this refrain from consuming the water and make sure your water is tested immediately. It is also wise to contact your water service provider.

To re-iterated, the only true way to know what is in your water is to get a comprehensive water test. This piece has only specified a few possibilities as ton what a on odour might be caused by. Smells and odours however can sometimes give you a general indication of some impurities in your water supply.

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