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North Marin Water District

Water Quality - Frequently Asked Questions


No, NMWD water is not fluoridated. Consult your dentist or pediatrician about your children’s fluoride needs.
NMWD’s Novato water is considered moderately hard.  Some appliance manuals refer to hardness in grains per gallon.  Your water hardness ranges from 5 to 7 grains per gallon (hard water exceeds 8.8 grains per gallon).  West Marin water hardness ranges are 3.8 to 8.0 grains per gallon.
Yes, we test our water annually for MTBE.  None has been detected.
Every winter and spring, the NMWD Water Quality Laboratory responds to numerous calls from concerned customers, particularly in Novato, about cloudy tap water.  This is a normal, naturally-occurring condition during this time of year and the water is safe to drink.  Entrapped air is typically the only cause of cloudiness.  The cloudiness should clear first from the bottom of the glass with the small air bubbles moving up toward the surface. 

Much of Novato’s water originates from 60 to 80 feet below the gravel beds adjacent to the Russian River.  At that depth, the water is under significant pressure especially when the river levels above the gravel beds are high.  In addition, this source water is very cold.  When water is both cold and under pressure, it is capable of holding significant amounts of dissolved oxygen or entrapped air.  When the water gets to your tap, it is generally a few degrees warmer and opening the faucet releases the pressure. 

To obtain clear drinking water, we suggest that customers draw tap water into a bottle and store it in the refrigerator.  It takes only a few minutes for the air bubbles to clear.

If you have any questions or are experiencing cloudy water that does not clear as described, please call the NMWD Water Quality Laboratory at (415) 897-4133, ext. 8520.

Two methods used by most are:

1. Boiling – boil vigorously for 3 minutes

2. Chemical treatment – use common household bleach.  If water is clear, add 2 drops per quart and let stand for 30 minutes.  If water is cloudy, add 4 drops per quart and let stand for 30 minutes.

This information is also provided in your local phone book.

When advised, water used for drinking, cooking, making any prepared drink, ice cubes or brushing teeth should be properly disinfected as noted above.

We test water in all our hydraulic pressure zones at least once a month.  If you are a NMWD customer and you are concerned about noticable odor or change in taste, call the NMWD Water Quality Laboratory staff at (415) 897-4133, ext. 8520.  Our staff may come to your home and collect samples to help identify any problem.

We want to know about water quality conditions so that we can determine the reasons and correct any potential system problems.

Water softeners remove calcium which can cause water spots.  Some individuals like soft water, others do not.  San Francisco has very soft water; San Diego has very hard water.  The NMWD water supply is moderate.  Using a water softener is a personal preference.  Most water softeners exchange two molecules of sodium for every calcium molecule removed, thus adding sodium to water consumed.  Consider this in your decision.
NMWD's Water Quality staff determines that complaints of bad tasting water result from the garden hose connections.  Luckily we have never determined that severe health effects have resulted; however, that condition has occurred elsewhere.

The most serious danger comes when a garden hose, connected to a faucet, has its free end in contact with a hazardous substance.  The substance could simply be bacteria-laden garden mud or dirty water in a child's wading pool.  The more serious contamination potential is from garden chemicals you use in spray attachments on your hose.

The bacteria and chemicals can get into your water pipes if there is a pressure drop in the water supply that could cause the hose, acting like a soda straw, to backflow or suck up whatever it was in contact with.  

When we get calls that a customer notices an odd taste in the water, we generally ask certain questions: "What kind of taste?” "Any particular time?” "How long has it been occurring?”  From experience, we have traced down the culprit on many occasions to the customer's garden hose, which has been fitted with a spray gun or other type of hose end shut-off valve.  In these cases, either the attached hose faucet is not turned off or it has a leak that allows the water in the hose to backflow into the house plumbing.  This occurs more frequently if the hose has occasion to get hot and expand, which results in intermittent plastic- or rubber-tasting water in the house. 

A REMEDY... Buy an inexpensive hose backflow prevention device.  These brass couplings fit at the hose faucet and prevent contaminated water from flowing back up into the pipes.  The cost is nominal but is a worthwhile investment.


·        NEVER submerge hose ends in buckets, tubs, pools, or sinks.

·        ALWAYS keep the hose away from possible contaminants.

·        ALWAYS disconnect spray attachments when not in use.

·        USE a backflow prevention device on hose faucets.

Discuss this issue with your medical doctor! There is always a small chance that tap water may contain something which may affect an immuno-compromised individual.  It is recommended by some medical doctors that immuno-compromised individuals filter tap water through a 1 micron filter or drink bottled water.
Cryptosporidium is a microbe that can cause a short-term intestinal illness in healthy individuals.  It can be very dangerous for immuno-compromised individuals because there are no drugs to kill the microbe.  Cryptosporidium is removed from water by filtration.  NMWD Novato water is filtered.
A cross connection is a condition that exists when a potable water pipe is connected to a non-potable pipe or another source of water (such as a private well).  A cross connection is dangerous because the connection makes it possible for non-potable and sometimes hazardous liquids to flow into the potable supply.  Under unusual pressure circumstances, it is possible that contaminated water could backflow through the water meter and contaminate the NMWD supply.

California health regulations require that property owners, who have the possibility of a cross connection occurring on their property, prevent any potential backflow by installing a backflow prevention device, either a "double-check valve" or a "reduced-pressure principle assembly."

For residential properties, state health guidelines cite some of the following conditions as warranting investigation and generally the installation of a device at the service meter:

·    Solar water heating systems

·      Auxiliary water system such as a well, a water storage tank, piped spring or creek water

·      Dock or pier with piped waterline or hose connection

·      Irrigation system with fertilizer feed

·      Spas or swimming pools without an "air gap" at entry of fill water.

If you have a spa or swimming pool and don't know if you have a proper "air gap," we are available to inspect it for you.  Our backflow prevention specialist will be glad to provide guidance to any of our customers on preventing backflow conditions or information on how to go about getting a backflow prevention device installed.  The backflow specialist can be reached at (415) 897-4133, Ext. 8603.