Lead and Copper

Corrosion Control Program

(updated December 15, 2023)

The City of Portsmouth implemented a Lead & Copper Corrosion Control Program in 2003 and has been in compliance with its requirements ever since. The general purpose of the Corrosion Control Program is to minimize the potential for water supplied by the City to leach potentially harmful metals such as lead and copper from pipes, fixtures and solder containing lead. The primary source of lead and copper in drinking water comes from internal household plumbing systems, plumbing components within other privately owned buildings, and the service lines feeding these properties. The City of Portsmouth water supply sources do not contain measurable quantities of lead.

Sampling conducted in 2023 throughout the Portsmouth water system found 16 locations with measurable concentrations of lead out of 121 residential locations. Of these 16 detections, only one exceeded the action level concentration of 15 parts per billion (ppb), while another was measured at 9 ppb, and the remaining tested below 4 ppb. This left a total of 105 water samples with no traces of lead (see figures below).

Fig 1. Portsmouth Water System's lead testing results from 61 residential samples collected and tested between January 1, 2023 and June 30, 2023.


Fig 2. Portsmouth Water System's lead testing results from 60 residential samples collected and tested between July 1, 2023 and December 31, 2023.


The following is a summary of the lead and copper compliance testing results and sampling schedule for the Portsmouth Water System since the Corrosion Control Program has been in place:


Corrosion Control Inhibitor 

To reduce the potential for City water to leach lead and copper from plumbing systems, a corrosion control inhibitor is added to the water supply. The corrosion inhibitor used by the City of Portsmouth is an orthophosphate/polyphosphate blended chemical that is a National Sanitation Foundation (NSF) Standard 60 additive approved for drinking water. The inhibitor creates a coating on the walls of distribution pipes and house plumbing to minimize the potential for metals (including lead and copper) to leach from pipes into the drinking water. It adds no noticeable taste to water. The optimized concentration in the Portsmouth water distribution system is 1 mg/L – as orthophosphate.

Ongoing Monitoring 

Portsmouth Water Treatment Operators continuously monitor the concentration of orthophosphate in the system. Automated analyzers, field measurements, and laboratory verification samples are analyzed to ensure optimized concentrations are maintained in the system. Additional water quality parameters that are factors in the corrosivity of water include alkalinity, hardness, dissolved solids, and pH. pH is continuously monitored and adjusted in the same fashion and frequency as orthophosphate, and alkalinity is monitored daily. The remaining parameters are monitored quarterly from the supply sources and selected locations throughout the distribution system.

Compliance Sampling 

As part of the Corrosion Control Program development, locations of representative residential household sampling sites are identified based on the five-tier priority ranking defined by the US Environmental Protection Agency (USEPA). Only those sampling sites that are approved by the New Hampshire Department of Environmental Services (NHDES) can be used for compliance sampling. The current tiered priorities are based upon the following site characteristics:

  • Tier 1 – Lead service line (LSL) Single Family
  • Tier 2 – LSL Multi-Family Home
  • Tier 3 – Galvanized requiring replacement
  • Tier 4 – Lead solder pre-1986
  • Tier 5 – Other representative site

During the first two years of the Corrosion Control Program, lead and copper compliance samples were collected two times per year at the 30 selected sampling sites. Upon confirmation of the effectiveness of the Corrosion Control Program, sampling was reduced to annually from 2005 through 2007, and to every three years thereafter. In 2018, due to the upgrade at our Greenland Well facility, the City of Portsmouth was required to sample 60 residences for lead and copper twice in 2018 (January to June, and July to December). This sampling requirement was subsequently reduced to 30 residencies, every year.  

Because a new groundwater source was added to the Portsmouth Water System toward the end of 2022, the sampling requirements doubled in quantity and frequency this year. This increase in monitoring is due to the blending of new water, with new characteristics, combining with existing source water traveling through the distribution system.

Public Outreach 

All of the participants in the residential compliance sampling program receive results of the lead and copper analyses with an explanation. Lead and copper results are available on the NHDES OneStop website.

Information about Portsmouth’s Corrosion Control Program has been distributed annually since its inception. Lead and copper information is summarized in the Portsmouth Water Division Annual Water Quality Reports.  

Testing Lead in Drinking Water in Schools and Daycares 

New Hampshire Senate Bill 247, signed into law on February 8, 2018, requires that all schools and licensed childcare facilities test for lead in drinking water at all locations where water is available for consumption by children. The first round of testing was completed by July 1, 2019. On July 8, 2022, House Bill HB-1421 was signed by the Governor. This law reduces the acceptable lead standard for schools and daycares from 15 ppb to 5 ppb, and sets forth sampling and remediation requirements. Any locations that have 5 ppb or higher of lead must be remediated. These programs are being administered by the NHDES and they are working directly with schools and daycares to gain compliance with this rule. All sample results are available on the NHDES website.