Drinking Water FAQ

Who controls my water’s quality?

The U.S. Environmental Protection Agency in Washington, D.C. sets national drinking water standards to protect public health. These standards are enforced in our state by the Pennsylvania Department of Environmental Protection. On a monthly or annual basis, we submit water quality test results to the state to prove that we are providing water that meets all of the standards. If there were ever a serious water quality problem, the state would immediately be notified and would oversee our response and corrective actions.

However, only a portion of what we do in testing water quality is driven by these federal or state requirements. We also perform tests not prescribed by federal and state laws. We test for the acceptability of the water’s quality, not just for its potential to meet the standards. We conduct research to better understand the characteristics of the water from the rivers to the tap, and to find better ways to treat and deliver water to our customers. In order to do all of this, we have set our own goals for water quality – goals that are more stringent than the federal or state standards. We continue reviewing these goals as new information comes in from around the world, and as better technology and science are developed, so that we can continue to provide the best tap water at the lowest cost.

What are the main characteristics of my drinking water?


Chlorine in the form of chloramine (chlorine combined with ammonia) is added, first to disinfect the water and then to make sure that the water stays free of germs and bacteria all the way to your tap. Chlorine levels in water vary from about 0.2 parts per million to 2 ppm depending on where you live relative to the water treatment plant, as well as the time of year (chlorine is harder to keep in the water during the summer when the temperature of the water is high).


Philadelphia’s water is moderately hard because the rivers from which we get the water contain calcium. We increase the hardness slightly as we add lime to adjust the acidity or pH level of the water. These are natural minerals


The acidity of Philadelphia’s water is controlled at the treatment plant using lime to make sure that treatment works properly and ensure that the water coming out of your tap is consistent and low in corrosiveness. The natural water’s pH can change. The treatment plants control these changes so that we can supply water that is neutral in pH.

Corrosion inhibitor

The U.S. Environmental Protection Agency and the Department of State require us to control the corrosiveness of our water to prevent lead and copper from leaching out of the plumbing materials into the water. We add parts-per-billion levels of a corrosion inhibitor, a phosphate, to the city’s water to reduce the corrosion of the pipes.


Fluoride is added to the water at 0.7 mg/L concentration for the prevention of tooth decay. This is done under the Philadelphia Department of Public Health’s guidance. Some fluoride is natural in the water – we boost it a little more to keep it consistent and beneficial.

Can I get my water tested?

The Philadelphia Water Department consistently tests the water supplied to the city. At our water treatment plants, where the drinking water is produced, we continuously run tests throughout the day, every day. In addition, we collect tap water samples from throughout the city on a daily basis and analyze the samples at our central laboratory. Our water has a very consistent, high quality. We test it for you to make sure it is safe and acceptable for drinking. Industries may need to have additional testing done.

Our water quality data is readily available to our customers as we publish a Water Quality Report every year. This report, available by calling the Water Department at 215-685-6300, might answer many of your questions. These reports are also located on our Water Quality page.

What is fluoride?

According to the CDC in 1999, the fluoridation of drinking water is considered to be one of the ten greatest achievements in public health in the 20th Century, as studies have shown that fluoride prevents the formation of, slows the progression of, and can even reverse newly-formed dental cavities.

Fluoride is a natural mineral and a form of the element fluorine (chemical symbol F), the 13th most abundant element in the earth’s crust. Fluorine combines with other elements such as calcium and sodium to form stable compounds (e.g., calcium fluoride or sodium fluoride) that exist naturally. Fluoride compounds are also produced by some industrial processes that use the mineral apatite. In humans, fluoride is mainly associated with calcified tissues (i.e., bones and teeth) because of its high affinity for calcium.

How is fluoride controlled by PWD?

Fluoride is added during water treatment. The major use of sodium hexafluorosilicate and fluorosilicic acid is as fluoridation agents for drinking water. PWD uses fluorosilicic acid in the treatment of its water since it is a high purity source of fluoride. This chemical meets strict NSF International standards for use in potable water.

PWD maintains a level of 0.6 – 0.8 mg/L, total fluoride in the drinking water. Fluoride is very stable, so that this level reaches every customer in the City.

PWD has operators and chemists 24/7 at its treatment facilities to constantly monitor the level of fluoride that is being added to the water.

Can I get too much fluoride?

Yes. The following is a summary of a report from the Committee on Fluoride in Drinking Water, National Research Council (Fluoride in Drinking Water: A Scientific Review of EPA’s Standards, 2006, National Academies of Sciences):

Exposure to fluoride can cause a condition known as enamel fluorosis. Depending on the amount of fluoride exposure (the dose) and the period of tooth development at which the exposure occurs, the effects of enamel fluorosis can range from mild discoloration of the tooth surface to severe staining, enamel loss, and pitting. The condition is permanent after it develops in children during tooth formation (from birth until about the age of 8). Severe enamel fluorosis occurs at an appreciable frequency, approximately 10% on average, among children in U.S. communities with water fluoride concentrations at or near the current allowable concentration of 4 mg/L. The prevalence of severe enamel fluorosis is very low below about 2 mg/L of fluoride in drinking water.

Fluoride is readily incorporated into the crystalline structure of bone, and will accumulate over time. Concerns about fluoride’s effects on the musculoskeletal system are focused on a condition called skeletal fluorosis and also on increased risks of bone fracture. Skeletal fluorosis is a bone and joint condition associated with prolonged exposure to high concentrations of fluoride. Fluoride increases bone density and causes changes in the bone that lead to joint stiffness and pain.

The US Centers for Disease Control (CDC) published its report on fluoride in 2001 (Recommendations for Using Fluoride to Prevent and Control Dental Caries in the United States, MMWR August 17, 2001 50(RR14);1-42) which summarized the following: Concerns regarding the risk for enamel fluorosis are limited to children aged < 8 years; enamel is no longer susceptible once its pre-eruptive maturation is complete. Fluoride sources for children aged < 8 years are drinking water, processed beverages and food, toothpaste, dietary supplements that include fluoride (tablets or drops), and other dental products. Children aged > 6 years are considered past the age that fluoride ingestion can cause cosmetically objectionable fluorosis because only certain posterior teeth are still at a susceptible stage of enamel development, and these will not be readily visible. In addition, the swallowing reflex has developed sufficiently by age 6 years for most children to be able to control inadvertent swallowing of fluoride toothpaste and mouth rinse.

Why is fluoride in my tap water?

For your health. The Philadelphia Water Department began adding fluoride to the water supply system, as a service to the Philadelphia Health Department, in compliance with the Philadelphia Health Code (ordinance 6-214), established December 5, 1951, and under permit provisions of the Commonwealth of Pennsylvania, Department of Public Health, issued July 22, 1952, at a concentration of 1.0 milligrams per liter (mg/L).

In January, 2012, the amount of fluoride added to the water was decreased in cooperation with the Philadelphia Health Department and the Pennsylvania Department of Environmental Protection so that customers now receive water containing 0.7 mg/L, as per new recommendations from the U.S. Public Health Service. The Philadelphia Water Department does not have the authority to cease feeding or alter the concentration unless directed by the Health Department of the City of Philadelphia, as stipulated by the Philadelphia Health Code.

Many public health agencies and experts endorse adding fluoride to the water as an effective method of preventing tooth decay in communities where natural fluoride levels are low. The “optimal” concentration range of fluoride in drinking-water for preventing tooth decay was set at a range of 0.7 to 1.2 mg/L more than 40 years ago by the U.S. Public Health Service, though they revised this range to the single value of 0.7 mg/L in January, 2011 in recognition of the increasing prevalence of fluoride exposure from other sources (such as toothpastes and processed beverages) and because regional differences in water consumption have evened out in recent decades.

The US Centers for Disease Control (CDC) published its report on fluoride in 2001 (Recommendations for Using Fluoride to Prevent and Control Dental Caries in the United States, MMWR August 17, 2001 50(RR14);1-42) which summarized the following:

Fluoride’s ability to inhibit or even reverse the initiation and progression of dental caries is well documented. The first use of adjusted fluoride in water for caries control began in 1945 and 1946 in the United States and Canada, when the fluoride concentration was adjusted in the drinking water supplying four communities. The U.S. Public Health Service (PHS) developed recommendations in the 1940s and 1950s regarding fluoride concentrations in public water supplies. At that time, public health officials assumed that drinking water would be the major source of fluoride for most U.S. residents. The success of water fluoridation in preventing and controlling dental caries led to the development of fluoride-containing products, including toothpaste (i.e., dentifrice), mouth rinse, dietary supplements, and professionally applied or prescribed gel, foam, or varnish.

The CDC also stated that:

The laboratory and epidemiologic research that has led to the better understanding of how fluoride prevents dental caries indicates that fluoride’s predominant effect is post-eruptive and topical and that the effect depends on fluoride being in the right amount in the right place at the right time. Fluoride works primarily after teeth have erupted, especially when small amounts are maintained constantly in the mouth, specifically in dental plaque and saliva. Thus, adults also benefit from fluoride, rather than only children.

Finally, the CDC summarized the following:

Widespread use of fluoride has been a major factor in the decline in the prevalence and severity of dental caries (i.e., tooth decay) in the United States and other economically developed countries. When used appropriately, fluoride is both safe and effective in preventing and controlling dental caries. All U.S. residents are likely exposed to some degree to fluoride, which is available from multiple sources.
Because frequent exposure to small amounts of fluoride each day will best reduce the risk for dental caries in all age groups, the work group recommends that all persons drink water with an optimal fluoride concentration and brush their teeth twice daily with fluoride toothpaste. For persons at high risk for dental caries, additional fluoride measures might be needed.

The American Water Works Association (AWWA) supports the recommendations of the World Health Organization (WHO), American Medical Association (AMA), Canadian Medical Association (CMA), Centers for Disease Control (CDC), American Dental Association (ADA), Canadian Dental Association (CDA), and other professional organizations in the medical community, for the fluoridation of public water supplies as a public health benefit. AWWA supports the application of fluoride in a responsible, effective, and reliable manner that includes monitoring and control of fluoride levels mandated by provincial, state, and/or federal laws and that is subject to community acceptance through applicable local decision-making processes. AWWA is committed to regular reviews of the most current research on fluoride and the positions of the medical and dental communities.

Even if PWD did not add fluoride to the water, small amounts would still be present. The natural level of fluoride in Philadelphia’s rivers is only about 0.1 – 0.2 mg/L.

Does PWD monitor for Chromium 6?

Chromium 6 is not regulated by Environmental Protection Agency (EPA) and PADEP. In 2014 PWD performed special monitoring as part of the Unregulated Contaminant Monitoring Rule, a nationwide monitoring effort conducted by EPA. Unregulated contaminants are those that do not yet have a drinking water standard set by EPA. The purpose of monitoring for these contaminants is to help EPA decide whether the contaminants should have a standard. PWD’s results averaged 0.34 parts per billion with a range of 0.30-0.42 parts per billion. The standard set by California is 10 parts per billion. Thus PWD’s results are substantially lower. PWD continues to follow the EPA’s ruling on this to ensure that we provide the highest quality water to our customers.

My water has a color to it, what should I do?

If your water has a brownish or rusty color, the color is a result of the presence of iron or rust. Most of the pipes in Philadelphia used to deliver water to your home are made of iron. Older mains can impart rust to the water. Newer mains are lined with cement to lessen the contact between the water and the iron mains. However, when there is an upset in the system such as a water main break, or when a valve is operated or water flow is changed, rust may be stirred up. When this happens, the water is unpleasant to look at and taste, but it is not harmful.

A rust problem is usually short-lived, and should be gone in a day or less once it is flushed from our water distribution system or your home plumbing. Do not wash clothes when water appears rusty because the rust will stain the fabric. Flush your cold and hot water, once the discoloration is gone, to make sure the rust does not accumulate or stay in your plumbing.

Should I buy bottled water or a home filter device?

The Philadelphia Water Department cannot recommend brands of products to buy. It is up to the customer to make a choice.

The main reason people might prefer bottled water is because bottled water does not contain chorine to control bacterial growth, and it therefore does not have the chlorinous flavor that tap water may have. But remember that bottled water can sit on store shelves for a long time before it is sold.

Home treatment devices are generally of little use in Philadelphia unless you have special needs, such as a laundry service that would benefit from softer water. Some carbon filters can remove the chlorinous flavor. Treatment systems must be properly maintained (filters changed in due time) or they will cause more problems than they prevent.

Home treatment devices should also be certified (for example, they should display an NSF seal) proving that they can do what they say they do.

Please refer to the Pennsylvania Department of Environmental Protection for more information.

What is that musty or earthy taste in my water?

Earthy and musty off-flavors in water occurs worldwide, and aside from the chlorine flavor of tap water, are the most common flavors noticed by our customers. They come from nature and have no known health effects at their natural levels.

Earthy and musty odors can be found in natural waters and in soils, as well as in beets and in corn (because they are grown in contact with soil). In waterways, when certain algae grow in abundance in what we call an algae bloom, high levels of these odors can be produced. Certain types of soil bacteria that also grow in water produce these chemicals, but they are less common in our waters.

The treatment needed to remove earthy and musty natural flavors can cost thousands of dollars a day. The most common treatment is to add carbon to the water as it is being treated, to absorb or soak up the flavors. However, these problems usually come and go, lasting for a few days to a few weeks.

The level of these flavors in water can be as low as 5 nanograms per liter (that is 5 parts-per-trillion – like 5 seconds in 320 centuries, or 5 pinches of salt in 10,000 tons of potato chips). Yet, highly sensitive people can still taste them. Sensitivity varies greatly among people. Many people are unable to detect one or the other flavor at their natural levels. Some people can detect both, equally well; the human senses are far more complex than anyone can understand.

Why does my tap water taste like chlorine?

Chlorine is added to water at the treatment plant to disinfect the water or rid it of harmful bacteria and germs. Chlorine is again added to the water before it leaves the treatment plant to prevent bacterial growth in the miles of pipelines from the plant to your home. There is always chlorine in the water but at very low levels.

In the 1970s, the Philadelphia Water Department began changing the way we add chlorine to the water supplied to the city. We began to combine chlorine (bleach) with ammonia to form a “chloramine” product. The chloramine product has less of a taste or smell than bleach chlorine. It also lasts longer, and does not cause the pipes to rust as in the case of bleach chlorine – so we have also reduced the rust problems in our water pipes.

So, in one sense, the taste of chlorine is a welcome taste. The presence of chlorine means that the water has been kept fresh.

There are ways to reduce the chlorine flavor in your tap water. A simple solution is to take tap water and store it in the refrigerator so that it is as cold as can be when you drink it. Colder water has less noticeable flavor. But you need to choose a good, clean storage jug, as some plastics impart a plastic taste to water.

There are people who are very sensitive to flavors. They may find it more difficult to ignore the chlorine taste in their tap water, although we have found that most people cannot taste the difference between bottled water and tap water. In the end, your own personal preference determines if you like the taste of your tap water.

How hard is my water?

The hardness of water is determined by the calcium and magnesium carbonates naturally dissolved in it. Across the U.S., there are waters that are very soft (low in carbonates) and waters that are very hard (high in carbonates).

When using soft water, one’s skin and hair feel soapy even after repeated rinsing. Hard water, on the other hand, makes the washing of clothes or the action of detergents more difficult. Very hard water leaves calcium scale or mineral deposits behind when it is heated up, and often needs to be softened.

Philadelphia’s water is moderately hard, and it may vary throughout the city. Depending on natural conditions, hardness could be higher or lower. For example, during a drought the hardness of the water increases as the calcium carbonates in the natural waters become more concentrated.

Hardness is measured in milligrams per liter or parts per million. Some washing machines ask for the hardness in grains per gallon. Soft water has about 1 grain of mineral per gallon. Moderately hard water has about 3 to 7 grains of minerals per gallon. Very hard water has over 10 grains per gallon.

The hardness of Philadelphia’s tap water is typically around 100 to 150 parts-per-million, which translate to about 6 to 9 grains per gallon.

Why have I found white or gray particles in my faucet’s aerator?

Particles can clog aerators and showerheads because of the small screens that often make up these fixtures. These screens may collect particles present in the water. The screens are called aerators because they break up the flow of water as it comes out of the faucet. The particles that get trapped on the aerators can come from a variety of sources. One of the most common sources is the hot water heater.

The same faucet delivers both hot and cold water in most homes. This is why material from the hot water heater can clog the cold water faucet.

There are dip tubes in heaters that direct the water to circulate and get heated. A dip tube is often made of polypropylene, a nontoxic plastic material. This plastic can break apart or disintegrate, and the small pieces can be carried away in the water to the faucet where they collect on the faucet’s aerator.

Why does my water appear milky?

If you have ever shaken up a warm bottle of soda, you know that all of the carbonation or carbon dioxide gas added in the production process wants to come out. If you open the top, the fluid will fizz up and over as the gas escapes to the air.

The same is true for tap water. When cold, such as during the winter, water is rich in oxygen. When it enters our homes, the water warms up and the oxygen wants to escape. You turn on the tap and, like shaking up that bottle of warm soda, the air fizzes up. As the glass of water sits, you will see the water clear from the bottom of the glass upward, as the air bubbles rise and escape into the air. All of these tiny air bubbles give the glass of water a milky appearance under natural or household lighting.

The air bubbles are not harmful and will quickly dissipate.

Why are there black particles in my water?

The most common cause of black particles showing up in tap water is the disintegration of rubber materials used in plumbing fixtures. Gaskets and o-rings can disintegrate over time and some pieces can collect in toilet tanks and around faucets.

Similar problems are often experienced in newly constructed or renovated buildings, as plumbers inevitably disturb the plumbing system when they do their work. A simple flush through the system may easily remedy the situation in most cases.

Why is there pink slime on my bathroom tiles?

Bacteria and molds grow well in moist environments, such as bathtubs, sink drains and bathroom tiles. A humidifier can also encourage mold growth.

These bacteria or molds are common and natural. They can be found in the air, in soil, in water, or on household surfaces. Orange and pink are common colors for many environmental bacteria such as, Pseudomonas and Flavobacterium.

Since the slime is caused by microbial growth on surfaces, cleaning and disinfecting using common household products, along with good hard scrubbing are the best means for controlling the slime growth.

It is a good idea to stay on top of these slime growths and scrub them away as they appear, as they can be irritants to sensitive people.

Can I get sick from my tap water?

The Philadelphia Water Department understands your concern. We often hear about people getting sick from water when they travel to foreign countries. Water in foreign countries is often not cleaned or disinfected as it is in the United States.

The Philadelphia Water Department tests the water daily, and in some cases, every three hours or on a constant basis, to make sure that it is free of harmful microorganisms. Philadelphia’s drinking water meets all state and federal safety requirements. The Water Department has an unblemished record in maintaining top quality water.

We do not find people getting sick from drinking the city’s tap water. There are so many other sources of germs that the concern over tap water in our city is minimal, although that is not true everywhere you may travel or for everyone you might speak to. The Philadelphia Water Department is working with the Philadelphia Department of Public Health to make sure that we maintain the healthfulness of water in our city.

Your primary care physician is your best contact for determining the cause of any sickness that you might have.

How can I better understand the levels of elements in my tap water?

The Philadelphia Water Department’s engineers and chemists measure and control what’s in the water, or remove from the water undesirable components. Our customers can find out a great deal about these particles from our annual Water Quality reports.

Tap water ingredients, like chlorine and fluoride, are measured at parts-per-million or milligram-per-liter levels – these are interchangeable terms.

1 part per million is similar to making a line of quarters from Center City to Conshohocken, and then walking that line to find the one quarter that is flipped up heads instead of tails.

Other substances, such as trihalomethanes, are measured at parts-per-billion or micrograms-per-liter levels.

1 part per billion is equal to 1 green apple in a barrel containing 1 billion red apples.

Finally, we also test for potential contaminants at parts-per-trillion or nanogram-per-liter levels.

Such contaminants include the naturally produced chemicals that can give water a musty taste.

1 part per trillion is similar to 1 inch in 16,000,000 miles or 1 penny in 10,000,000,000 dollars.

How corrosive is my tap water?

Water is often said to be the universal solvent. Given enough time, it will dissolve almost anything, including materials used in water mains and building plumbing.

Water mains in Philadelphia are made of iron, while most of the plumbing is made of copper, with a minimal lead content. In a process called corrosion, these metals (lead, copper, and iron) may dissolve from the pipes and get into your drinking water.

The Philadelphia Water Department takes corrosion seriously for two reasons. First, corroded pipes become weak and must be taken out of service. Second, the dissolved metals or corrosion products may degrade the quality of our drinking water (the water can taste metallic) or in the most serious cases they may become a health concern (as with lead).

Although the city’s waters are not particularly corrosive in their natural state, the Philadelphia Water Department adjusts the quality of the water to keep corrosion as low as possible.

There are two ways that we optimize water quality to reduce corrosion. First, we make sure that the acidity, or pH, of the water is around 7.4 units. At 7.4, the water is slightly basic, rather than acidic. The other way that we optimize water quality to reduce corrosion is by adding parts-per-million levels of phosphates to the water at the treatment plants. The phosphate, in combination with the natural calcium and magnesium minerals in the water, coats the pipes internally to prevent the iron, lead and copper from escaping. Phosphate is simply made up of phosphorus (an essential element for all living beings) and oxygen. They are common in the environment, especially as nutrients for plants, and are very useful to us for reducing the corrosion of our pipes and your plumbing.

Should I boil my tap water?

In general, you should not boil your tap water. Your tap water, as delivered by the Philadelphia Water Department, is safe and does not need to be boiled in order to drink it. Boiling water increases the risk of scalding or burns. This risk is typically much more significant than any benefits you might receive from boiling the water.

If there was a need to boil water to rid it of microbial contaminants, such as Giardia, Cryptosporidium and harmful bacteria, then the rule of thumb is to bring the water to a rolling boil for one minute. For example, people who go camping in the mountains are advised to boil their spring water before drinking or cooking with it.

Does boiling improve the taste of tap water?

It is unlikely that you will notice any taste difference. The primary reason for the taste of tap water is the chloramine (chlorine) that is in the water. This gives the water a slight chlorine taste. The chloramine is there to maintain the freshness of water throughout the City. Chloramine is used because it is persistent. Boiling water for five minutes might only reduce the chloramine level by half. It will not get rid of the chloramine. Placing the water in the refrigerator in a water jug will help to reduce the chlorine taste since colder water has a less noticeable taste.

Are there bacteria in my water?

Water, air, food and our environment in general are not sterile. In fact, our immune systems need a certain degree of contact with germs to develop defense mechanisms to guard our health (the basis for inoculations and immunities). However, we should be sanitary and safe from harmful levels of microorganisms.

The Philadelphia Water Department tests the biological quality of the tap water delivered to our customers to make sure it is sanitary and safe. We add chlorine to disinfect our water (free it of harmful organisms).

As a result of our effective water treatment processes, including the use of chlorine, the quality of public health in Philadelphia is high. Philadelphians do not suffer from the water-spread diseases present in many communities around the world. The Philadelphia Department of Public Health educates people on disease prevention, and makes sure that any diseases are treated early on to prevent their spread.

For most people with healthy immune systems, the natural microorganisms in water, foods and the air are not harmful. Those with special needs should consult their primary care physician who can contact us for more specific information.

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