Boiler Antifreeze

To our Valued Customer,

Since at least 1992, but possibly earlier than that, the State of New Hampshire has required that All boilers that have Anything other than clear water in them to be protected by a testable reduced pressure principle backflow preventer or RPZ type Backflow Preventer in order to positively ensure that no fluid from the boiler can be drawn into the drinking water of the house or the community and contaminating you and your community’s drinking water. This is for your protection and the protection of the community drinking water supply. These requirements can be found in RSA 155-A of the New Hampshire State Building Code under

The Plumbing, the Mechanical, and the Residential Code Books.

              The Plumbing Code Book 2009:

608.16.2 Connections to Boilers

               The Mechanical Code Book 23009:

                              1005.2 Potable Water Supply

               The Residential Code Book 2009:

                              M2101.3 Protection of Potable Water

                These requirements need to be met by Anyone who installs, services or maintains a water or steam boiler that are connected to a fresh water supply regardless of whether they are a professional and licensed person or a handyman/maintenance person. The State of New Hampshire allows no exceptions to these requirements.

               This information is to help you to understand our policies regarding the installation of antifreeze into your boiler systems this better.. You may have had anti-freeze for years or just recently added it and you have been told by our technician that you need a  RPZ type backflow preventer. Also, I cannot speak for other company’s policies or why they did not tell you, but I am personally and professionally responsible to do it the right way the first time. Once again this is protection for you, your community, and the environment.  Thank you for your attention to this matter.

When anti freezing any boiler certain considerations need to be addressed


  • Antifreeze requires a certain amount of maintenance after the initial installation we recommend that it be checked after the second year for strength and for PH level we have found that most systems will  require some adjustment at this time
    • It is a water soluble product and does break down in water
      • It does not release or transfer  the heat it carries as easily as water and there can be as much as 17% less heat transfer
        • The molecules of antifreeze are smaller and thus they leak out of places where water normally doesn’t
          • If your system is not piped for antifreeze. There maybe additional costs in installing and maintaining your boiler antifreeze
          • RPZ’s backflow preventers are required to be tested twice a year by a certified backflow tester
                • Aluminum boilers require special aluminum antifreeze
                  • If not properly installed the antifreeze can create sludge problems in certain system types       





Below is pictures of a Non RPZ type Backflow device and a RPZ type Backflow Preventor

Non RPZ Type Backflow Device
RPZ Type Backflow Preventer