Water Quality

COVID-19 Update

We want to reassure residents that the coronavirus is not spread through tap water. NBRID uses a microfiltration membrane plant for treatment and chlorine post treatment to eliminate pathogens (this includes viruses) to ensure drinking water is safe. Your drinking water is tested regularly to ensure it meets all safe drinking water standards.

For questions about the coronavirus, please visit - https://www.countyofnapa.org/2739/coronavirus


Monitoring and Testing

NBRID’s raw water supply comes from Lake Berryessa from a deep intake pump station location just to the north of the water treatment plant. Before this water reaches your tap, NBRID operators take many steps to ensure it meets drinking water standards. This includes performing regular testing; NBRID provides water testing up to the water meter. Beyond the water meter, the plumbing system belongs to the customer. If you are concerned about your home's private plumbing, you can have your drinking water tested by a private laboratory.

NBRID takes its responsibility for providing the community safe and reliable drinking water very seriously and ensures that the water supply meets or exceeds all U.S. Environmental Protection Agency's and State Water Resources Control Board safe drinking water requirements. The water system is monitored 24/7 and maintained by a team of highly skilled operators, engineers, technical experts, and administrative staff. In addition, NBRID actively monitors the watershed for any potential changes in water quality. 

Disinfection Byproducts

The District’s Water System is currently meeting the regulatory standard for Disinfection Byproducts (DBPs) in Drinking Water. The City of Napa created an FAQ for DBPs (PDF) that may answer your questions about what they are and why they are formed in drinking water.  

The byproducts of interest for our water system are Trihalomethanes (THMs) and Haloacetic Acid (HAA5). Levels of HAA5 in our drinking water have remained within compliance since testing began in earnest in 2004. During the past year, however, you should have received quarterly notices in the mail regarding the presence of THMs above the maximum contaminant level (MCL) caused by the reaction of chlorine with organic matter in potable water. The District is pleased to report that the water system’s current running annual average (RAA) fell below the MCL of 80 ppb (parts per billion) set by the EPA and regulated by the State Division of Drinking Water, and the District is now in compliance with regulations. Should this change during any sampling event in the future, we will notify you once again through another mailing.

NBRID - Jar Testing

District staff have spoken with many customers about the complex nature of THMs, their presence, causes, and steps the District has been taking to prevent their formation. District Engineers and Operations staff are constantly adjusting treatment processes and looking for new and unique ways to reduce the possibility of THM formation in the system.  Use of the of the above pictured Jar Testing apparatus is common to fine-tune chemical doses (coagulant and disinfectant) to optimize treatment for removal of THMs and its precursors (dissolved organic matter reacting with chlorine, etc.).  

The following is a list of all projects recently completed to assist with removal of THM precursors and also THM once is has formed:

•  Precursor Removal:

  • Pre-Settling Tank at the Water Treatment Plant (2020) 
  •  Pre-Treatment Pressure Tanks to increase flocculation (2017)

•  THM Removal:

  • Aeration and Mixing at the 500,000 gallon tank (2020)
  • Aeration and Mixing at the 70,000 gallon clearwell tank (2020)

Regulatory Documentation


Annual Water Quality Report

Our drinking water routinely meets or exceeds water quality standards set by the Environmental Protection Agency and the State Water Resources Control Board. Every year, pursuant to the Safe Drinking Water Act, NBRID publishes and distributes a Water Quality Report, which lists regulated constituents found in our drinking water.

To find out more about water quality reporting and/or to view our Annual Quality Reports, please follow the links below:

Hydrant Flushing

The District flushes the water system through it’s hydrants throughout the year. 

Hydrant flushing is an important maintenance activity to clean and flush District water mains. Fire hydrants are opened to move a large volume of water at a higher-than-normal velocity through the mains. This procedure mobilizes particles and minerals that have settled over time and flushes them out of the system. This activity assists the District in maintaining the highest quality of water in the public water system.

Hydrant flushing is also used to find hydrants that need maintenance or need to be replaced. It is expected that all of the District’s hydrants will be flushed at least twice during the year – with additional hydrant inspections happening prior to warm, dry weather months.

Lead & Copper Rule

NBRID’s drinking water is very low risk for lead contamination. Our water mains are typically AC (asbestos-cement) and steel, and service lines are typically copper or plastic. Lead service lines are not common, and all new household plumbing fixtures are required to be lead free. 

Even with the unlikely occurrence of lead pipes or lead solder connecting pipes, the Lead and Copper Rule requires water systems to test water from customer faucets to ensure no leaching of lead or copper from household plumbing is occurring. We are required to conduct this testing every three years.

Our most recent lead and copper sampling event occurred at the end of July 2020 and all results were well below the MCL for both lead and copper; the system is in compliance with the Rule.

Reporting a Problem with your Drinking Water

Before reporting a problem, please note whether your concern is with the water’s color, taste, odor, pressure, or something other, and be prepared to answer the following questions:

  • Is the problem in the hot water, cold water, or both?
  • Is the problem observed at all faucets?
  • Do neighbors see a similar problem?
  • Is there construction activity nearby?
  • How long have you noticed the problem?

Call the District main office at (707) 259-8600, or the District’s operations team at (916) 584-1893.

Helpful Sites

You can find more information about the topics above by following the links below: