Why does my tap water smell bad?

It’s interesting how many times I’ve been asked that question, and by whom.  To answer the question however, we first need to know where the water comes from. 

First off, is your drinking water coming from surface waters, like a lake or stream or is it coming from groundwater, like an aquifer with a well drilled into it?

Surface waters, in general, will tend to have odors associated with them that can best described as “earthy” or “grassy”.  This is because surface waters are open to algae growth, and receive inflow from the land surrounding them.  That land generally has plants and organic matter on it, which is the primary cause of the odor and can sometimes act as a food source for algae.  In addition, surface waters that do have algae issues will have an earthy odor.  The natural question is “is this dangerous?”  The good news is no, it’s not.  While it makes the water less enjoyable to drink, it doesn’t make it dangerous.  There are some newer treatment technologies, such as dissolved air floatation, which uses very tiny air bubbles to pass through the water.  As they rise through the column of water, they grab on to the odor compounds, along with a host of other debris in the water and float them to the top of the treatment tank.  There this foam is removed and clear water is passed on to the water treatment plant for additional treatment.  There are also treatment options that use active carbon to adsorb the odor compounds before the water leaves treatment.

If you have groundwater, then the taste and odor compounds are a little different.  You are unlikely to have organic odors, but are much more likely to have sulfur odors, or metallic odors.  This is generally because groundwater is in contact with all sorts of minerals that can impart these odors.  Again, you might wonder if these are dangerous, unfortunately there isn’t a simple answer to that.  It really depends on the minerals the water flows through.  If there are sulfur deposits, heavy metal deposits or even in some cases radiological compounds there could be some danger to prolonged consumption, especially by those persons who are elderly or in poor health.

Sometimes, regardless of the source, you might notice a chemical odor, like a bleach smell for instance.  Don’t panic, that’s not a bad thing.  Most public water supplies in America use some form of chlorine to disinfect the water.  Public water systems are required to maintain a residual of their chosen disinfectant in the distribution system and up to your home.  That chlorine odor means you have a strong residual present.  There are limits however to how strong the residual can be.  If you have concerns, please contact your utility.  They want to hear from you, after all they cannot be everywhere all the time, so positive contacts with their customers help them ensure that the system is working right.

One final common odor and color causing problem is related to in home water filters and water softeners.  These devices remove the disinfectant from the water coming into your home.  While that’s not a bad thing necessarily, you need to be sure to have these devices serviced regularly.  They need treatment chemicals, and have various controls that need to be properly set to ensure they work properly.  If they are not being serviced or incorrectly configured they can degrade water quality and place your home at risk for waterborne pathogens, taste and odor problems and even discolored water.  In general, you will need a plumber to service these devices if you can’t do it yourself.  The vast majority of utilities cannot legally perform work on them for you.

Your water utility is required to comply with state and federal laws regarding source water quality.  These rules are generally stringent and set levels of exposure that are well below the actual exposure levels that might pose a health risk. 

If you have questions about your water quality, call your water provider and ask for a Customer Confidence Report, or the most recent water system annual quality report.  Depending where you live the name of the report could be different, but they will understand what you are asking for and can provide it.  In fact, in America they are legally required to provide it on request as well as send it out in the mail or a bill annually.