Water Quality FAQs

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PWP Water Service

How much water is used daily in Pasadena?
PWP customers use, in total, approximately 27 million gallons of water each day.

Is Pasadena’s water safe to drink?
Yes. The water delivered to your water meter meets all state and federal drinking water standards and is safe to use without further treatment. However, you are responsible for plumbing and treatment devices installed on your property. Substandard, illegal, old, poorly maintained or improperly installed plumbing or water treatment devices may adversely affect your water quality.

How does PWP test the water?
PWP is required by state and federal law to regularly test the water. We have a crew of state certified field and laboratory personnel who sample and test the water every day, at at 300 locations around the City. There are over 170 different constituents in the water that are tested by PWP. The amount of each constituent allowed in the water and the frequency with which we test for each constituent is regulated by the California State Water Resources Control Board Division of Drinking Water (DDW) and by the United States Environmental Protection Agency (USEPA).  Review our annual Consumer Confidence Report on Water Quality to learn more about the stringent testing and tough water quality guidelines PWP meets each year.

How can I have my water tested?
If you have a specific concern (e.g. lead contamination from your plumbing), or you would just like to verify our test results, services for water testing are available from commercial and environmental laboratories for a fee. The fee depends on the number of constituents you would like tested in the water. A simple lead test will usually cost around $30-$50. If you would like to test your water for everything that PWP tests for, it will easily cost over $1,000. You can obtain references for qualified laboratories by contacting the California State Water Resources Control Board Division of Drinking Water.

Do water filters work and should I use one?
As with most products, some filters work better than others. If you install a water filter, follow the operating and maintenance instructions very carefully. An improperly installed and/or maintained filter can adversely affect the water quality. There are many types of filters available, each type works differently and will remove different substances from the water. It will be very helpful for you to know exactly why you want to filter the water before you speak to a seller of water treatment devices.

If you choose to filter your water, there are several resources available to assist you in choosing a filter that works properly and will meet your needs. You may call the National Sanitation Foundation International for a list of approved water treatment devices.

How is water quality measured? 
Water from PWP's groundwater wells, imported water from MWD, and purchased water from neighboring water agencies are of high quality. These water sources may taste different because they have different mineral contents. While water quality is measured by chemical and biological analysis, taste is determined by mineral content and the disinfectant processes. Taste may vary depending on where water comes from and how it is treated.

What can I safely pour down the sink or into the toilet?
If your home is on a municipal sewage system, the following can be safely poured down a drain, followed by flush water: disinfectants, rust removers, hair relaxers, water-based glues, drain cleaners, aluminum cleaners, window cleaners, and photographic chemicals. A hazardous waste contractor should dispose of all other liquid home products. A similar type of list has not been developed for homes with a septic tank. Contact the Department of Public Works to get information on the disposal of specific products.

What are the causes of low water pressure, and should low water pressure concern me? 
Temporary low pressure can be caused by heavy water use in your area – lots of lawn watering, a water main break, fighting a nearby fire, etc. Permanent low pressure could be caused by the location of your home – on a hill or far from the booster pump plant – or your home may be served by pipes in the street that are too small.

Low pressure is more than just a nuisance. The water system depends on pressure to keep out any contamination. If the pressure drops, the possibility of pollution entering the drinking water increases. You should report any permanent drop in water pressure to PWP by calling our water emergency hotline.

My water faucet drips a little; should I bother to fix it? 
Yes. Drips waste a precious product, and this waste should be stopped, even though the dripping water may not register on your water meter. To find out how much water you’re wasting, put a measuring cup under the drip and find out how many minutes it takes to fill it up. Divide the filling time into 90 (90 + minutes to fill) to get the gallons of water wasted each day.

How does PWP know how much water I use in my home? 
Most households have a water meter that measures the amount of water used in the home. The water meters are read automatically on a regular schedule. The previous reading is subtracted from the current reading to determine the amount of water actually used.

How does PWP know that my water meter is accurate? 
PWP has programs to routinely test water meters. This is done on a rotating basis to make sure the meters are accurate. Of course, if your recorded water use changes suddenly for no obvious reason, report this to PWP so it can be investigated. Note, additional people in the home, a sprinkler leak and/or excessive lawn watering can make your water bill higher.

Where does the water go when the toilet flushes?
It goes into a sewer pipeline system that flows into the Los Angeles County Sanitation district’s wastewater treatment plant where one of two things will happen following treatment: it will become recycled water for irrigation purposes or discharged into the ocean.

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Drinking Water

Is it okay to use hot tap water for cooking?
Not from the tap: use cold water instead. Hot water is more likely to contain rust and lead from your household plumbing and water heater.

If I want to kill all of the germs in my drinking water, what should I do? 
Boil the water for 5 minutes (use a timer) after it reaches to a full boil on a stove or in a microwave oven. Do not count the time it takes for the water to reach full boiling. This should be done during emergencies only because this process uses a lot of energy and concentrates some chemicals (nitrates and pesticides) if they are present in the drinking water. However, the advantage of killing the germs outweighs the disadvantage of the slight worsening of water quality (concentrating the chemicals).

Why does my drinking water sometimes appear cloudy or milky? 
Air in the water can create a cloudy or milky appearance. Turning on a faucet releases pressure in the water piping system, causing hundreds of tiny air bubbles to form. Like the carbon dioxide in soft drinks, the air bubbles will disappear after a few minutes.

Why does my drinking water sometimes have a reddish or yellowish color? 
Rust in household water pipes or in water pipes under city streets can create the reddish or yellowish color. The rust is a compound of iron and oxygen that is harmless in drinking water but can stain clothes and porcelain fixtures. Some rusting color is most noticeable after pipe repairs or during periods of low water use. To determine the source of rust, let water run from a faucet in your home. If the water clears after a few minutes, the rust may be coming from household water pipes. If the water clears only after a long period of time, the rust may be coming from city water pipes. Learn more on our Troubleshooting [4.6.2] page.

Why does my drinking water taste or smell “funny,” and is make me sick? 
The three most common reasons for bad tasting or smelling water are: a funny taste can come from the chlorine that is added to the water to kill germs; A harmless, smelly chemical---hydrogen sulfide---dissolved in the water causes a rotten-egg odor in some groundwater; As algae grow in surface water sources, they give off harmless, smelly chemicals that can cause unpleasant tastes in drinking water. If you are concerned about the taste of your tap water, please call PWP Customer Service.

What can I do if my drinking water taste or smell “funny”? 
Here are few suggestions you can take if you detect a funny taste or smell in your water;

  • Store drinking water in closed glass container in the refrigerator. Warm drinking water has more taste that cold drinking water.
  • Mix the drinking water in an electric blender for 5 minutes. Mixing the water may remove some of the bad taste but not all of it.
  • Some people are sensitive to chlorine taste and smell. Boiling the water for 5 minutes should remove most, if not all, of the chlorine.
  • Adding 1 to 2 teaspoons of lemon juice to refrigerated water may result in pleasant tasting water.

Why is disinfectant added to the water?
Disinfectants, such as chlorine, stop bacteria from growing in water pipelines. PWP uses disinfectants where necessary throughout the water system. If the slight chlorine taste or smell is bothersome, you can chill your water overnight in the refrigerator or boil it for 5 minutes. The chlorine compounds will dissipate reducing the smell and taste.

Why can’t ocean water be treated to make drinking water? 
Ocean water can be treated but building and operating a desalination plant and transporting the water to Pasadena would be too expensive. The cost of converting saltwater to drinking water has been estimated at $5 to $7 per 1,000 gallons. Ocean water is extremely salty and would take a substantial amount of energy to convert it to drinking water.

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Metropolitan Water District of Southern California (MWD) supplies about 60% of Pasadena's drinking water. In October 2007, added fluoride to their water supply. Before drinking water is delivered to your home or business tap, the fluoridated MWD water will be blended with Pasadena groundwater. Here are answers to frequently asked questions about fluoride in drinking water:

What is fluoride?
It is a naturally occurring compound derived from fluorine, an abundant element in surface water (lakes, rivers & oceans) and groundwater (water from rain that soaks through the soil and into an underground reservoir)

What are the benefits of fluoride? 
According to the Centers for Disease Control and Prevention (CDC), the fluoridation of community drinking water is the most cost effective and safe way to reduce and control tooth decay. More than 50 years of scientific research has led to the conclusion that people who live in communities with fluoridated water have healthier teeth and fewer cavities than those living where water is not fluoridated.

How much fluoride will MWD add to Pasadena's community drinking water? 
MWD's water naturally has 0.1 to 0.4 parts per million (ppm) of fluoride, and they want to increase that amount to 0.7 to 0.8 ppm. Since Pasadena's groundwater has a naturally higher fluoride level of 0.8 to 1.4 ppm, the resulting new concentration will be 0.7 to 1.2 ppm in our community drinking water.

How is "parts per million" defined? 
To put it simply, if there are a million "parts" - teaspoons, for example - then 1 part per million equals 1 teaspoon of a substance mixed in with one million teaspoons of water.

What if I don't want to drink fluoridated water? 
Home water treatment units that use reverse osmosis membrane filters can effectively remove fluoride from tap water. Most bottled water does not contain fluoride; check the label to be sure.

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Soft vs. Hard Water

What is hard water?
Hardness in drinking water is determined by the amount of calcium and magnesium it contains. These minerals are harmless, but they can cause temporary white spots on glasses and make soap difficult to lather. Pasadena’s water has an average hardness of 12.9 grains per gallon and it is considered to be very hard. There is no known health effect that is caused by hard water. Like other minerals, calcium and magnesium are beneficial to human health.

Why does my water sometimes look cloudy and is hard? Is this safe?
Some Pasadena residents have noticed that their tap water can be unusually hard and/or cloudy. Both of these issues can be traced to the drought’s effect on our water supplies. Neither of these issues poses a health risk. The cloudy or milky/white appearance is due to air bubbles. The amount in PWP’s water is higher than normal because the local water table is lower than it has been for quite some time. With lower water tables, PWP’s wells draw more air into the water when it is pumped out. When this water is delivered to customers’ taps, it often comes out appearing cloudy, or milky/white. This will clear in a few moments if allowed to settle. PWP water quality officials want to reassure Pasadena residents that there is no cause for concern about the health impacts of hard water.

How does water become hard? 
Water becomes hard as it passes over or through certain geological formations that contain calcium or magnesium. For example, groundwater becomes hard as it percolates down to the water table though limestone deposits containing calcium, or though dolomite and other magnesium bearing minerals that dissolve into water. Surface water imported to Pasadena is hard because it has passed over similar formations as it flows hundreds of miles from the Colorado River and from the streams in Northern California.

When should you expect hard water in Pasadena?
Because the source of PWP’s water varies at different times of the year, the hardness of our drinking water also varies. Typically, the water is the softest from May to September when we rely on groundwater from local wells. Our water is the hardest from October to April, when PWP purchases more imported surface water from Metropolitan Water District of Southern California (MWD).

How is hard water softened?
Household water softeners typically use salt to reduce hardness in water. As water passes through the unit, sodium atoms in the salt replace calcium and magnesium atoms. Some cities have banned the use of water softeners because they discharge a waste that contains large amounts of chloride. Over time the salt-bearing unit must be changed or recharged to remain effective. In purchasing a water softener, be aware of various recharging procedures, since these vary significantly from model to model. If you do install a water softener, follow the operating and maintenance instructions very carefully.

What are the advantages and disadvantages of soft water? 
Soft water can help maintain the unobstructed flow in water pipes and extend the life of bathtubs, sinks, and toilets by minimizing the buildup of mineral deposits. It can also reduce soapy films on tubs and shower tiles, promote thorough rinsing of shampoos and soaps, and improve the efficiency of water heaters. Washing clothes in soft water requires less soap. Excessively soft water can cause corrosion in pipes. Also, increased levels of sodium in softened drinking water may pose a health consideration for some people on restricted sodium diets.

Why does my dishwater leave spots on my glasses? 
Harmless minerals that remain on the glass when the water evaporates cause the spots that may appear on glassware after it is washed or air-dried. Commercial products are available that allow the water to drain from the glassware more completely. Spots on glass shower doors appear for the same reason.

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PWP Water Supply

Where does tap water come from?
There are two major sources of tap water: surface water, and groundwater. Surface water comes from lakes, reservoirs, and rivers. Groundwater comes from wells that are drilled into aquifers. An aquifer is an underground geologic formation through which water flows slowly.

Where does PWP water come from?
About 41% of the supply is groundwater from the Raymond Groundwater Basin and is pumped out of 16 deep wells located throughout Pasadena, 58% of the water is imported from the Metropolitan Water District of Southern California (MWD) and consists of a blend of water from Northern California and the Colorado River. The remaining 1 percent is purchased from neighboring water agencies that combine surface water and groundwater.

How is the Groundwater in the Raymond Basin replenished?
Rainfall is the main source of water that replenishes the Raymond Groundwater Basin. PWP and other water agencies only pump water out of the Raymond Basin that is equal to what is naturally replenished. During a drought, however, the groundwater levels will slowly drop because there is little or no rainwater or mountain runoff to replenish the basin.

What is the Hahamongna Watershed Park?
The Hahamongna Watershed Park (HWP) is approximately 1,300 acres of open space extending up the Arroyo Seco Canyon from Devil’s Gate Dam. There are four water wells within the HWP basin owned by the City of Pasadena.

What is the Devil’s Gate Dam?
The Devil’s Gate Dam was constructed in 1920 and renovated in 1998. It is used for flood protection and as a water reservoir to recharge the Raymond Basin Aquifer. The Devil’s Gate Dam is owned by Los Angeles County Public Works.

What are the major components of the PWP water distribution system?
PWP has 16 active wells that feed groundwater into various reservoirs. There are 18 reservoirs throughout the city that hold well water and purchased water from the Metropolitan Water District. Jones Reservoir, PWP’s largest reservoir, can hold about 50 million gallons of water and Lida Reservoir is the smallest with a 0.43 million gallon capacity. The water is disinfected and blended in the reservoir then distributed to the customers through a pipeline network of 502 miles of mains throughout the city.

What is being done to protect Pasadena’s water supply from current or future contamination?
PWP conducts sanitary surveys of the Arroyo and Eaton Canyon streams regularly. These streams supplement our groundwater supplies. The Department of Public Works has waste disposal programs so that customers can remove hazardous materials appropriately.

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What to Do During an Emergency

Water is vital to everyday life, necessary for health and should never be taken for granted. It is very important to be prepared for water emergencies BEFORE they occur. Earthquakes, floods, high winds, droughts and forest or brush fires are events that can create water emergencies. Likewise, broken water mains, power outages, treatment plant breakdowns, and failure of storage tanks or equipment are considered "water system" emergencies.

Learn how to shut off the main water valve to your house. Make sure you know the location of the valve; have the necessary tools to operate it; and mark it with fluorescent paint or tape for locating the valve in the dark.

Purchase bottled water or store water in clean unbreakable containers that can be properly sealed or capped after filling. It is recommended to have at least one gallon of water per person per day (remember to store for pets too), and store enough water for three to five days. Keep water stored in a cool area away from direct sunlight. Water should be replaced every six months.

If you must use tap water during a water emergency, make sure your water has been disinfected by boiling it for 5 minutes or you can use water-disinfecting tablets (4 tablets per gallon), tincture of iodine (12 drops per gallon) or liquid chlorine (8-10 drops per gallon). After treatment, mix the water thoroughly and let it stand for 30 minutes before use. If the water has been chemically polluted, these methods will not disinfect your water: Do not use this water.

For more information about how to prepare for an emergency click here.