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Backflow Preventer Location

hausfxr Member Posts: 1
I’m heating my home with an in-floor hydronic system I installed myself. I got lots of advice from online forums 10 years ago and markedly diffing opinions on system configurations and components, and I ultimately decided on the simplest design that would be easy for a DIYer to complete. The system seems to work perfectly and so far my only real complaint is that the Water Furnace ground source heat pump makes a bit of noise for the first 10 seconds or so after starting, but it’s not that bad if you keep the utility room door closed – my HRV is louder than the heat pump after that initial startup.

The system has been inspected five times by the City of Portland Oregon: once at HVAC final for the my basement renovation when I first installed the system six years ago; once more at the plumbing final for the basement; again at HVAC rough-in for the upper floors in 2017; once more at upstairs plumbing rough-in; and, finally, at HVAC final last summer. There were five different inspectors, and all of them discussed the hydronic system briefly and I got the impression that for some of them, this was their first time seeing a hydronic system or at least my particular setup. All approved the work as is.

I got what we hoped would be our last inspections for finish plumbing and occupancy the first week of December, and this inspector really took a long time looking at my heating system and I had to explain the different components to him. I could tell he was struggling with understanding it and finally he said we needed a backflow valve somewhere in the system, but he could not tell me where. I gave him a copy of the diagram of the existing system and he said he’d talk to his supervisor and get back to me. After two weeks of not hearing from him, I contacted plumbing inspections and talked with a senior inspector (turns out he was the inspector who did the upper floors plumbing rough inspections, so we’d already discussed the hydronic system, but I did not mention that to him in our latest contact). At his request, I sent pictures of the system. His response was this:

“Looking at the pictures for the backflow protection I cannot tell if it is the proper type or in the proper location. There should be what is called an R.P device on the potable water as it enters the system. The device pictured is not a RP and I cannot tell if it is properly located. Please finish the rest of the corrections and call in for you final inspection.”

Doing some online research, I found the portion of the code and other references describing separation of non-potable water systems from the potable water with an RPZ valve, but could not find any specifics on its proper location. Not sure it’s relevant, but my hydronic closed loop system has just water in it and no glycol – all of the ½” PEX loops are continuous with no metal fittings from the manifold supply to their return, so the PEX lines (theoretically) could freeze solid and never leak. But in any case, the potable water needs protection from the stagnate closed loop water. I then sent the attached diagram to the inspector with proposed RPZs and I have not heard back from him in three weeks.

So, here’s my thought and reason for describing the inspections regime experience in such depth on this posting. It appears that neither the senior inspector or the inspector who looked at the system most recently know exactly what is required to meet the code. I know that if I just put the RPZ in and call for an inspection, the field inspector will be satisfied. However, I want to put it in the proper place that protects both my potable water and the City’s water and I know someone out there knows both best practice and code requirements. Any advice would be appreciated.

As a side note, the company who installed the heat pump and 120 gallon water heater, Total Energy Concepts, Inc., did not hook up the existing plumbing to it or the electrical for the water heater’s heating element. After they left and did not return, I called them and they said they never do that and that I would need a licensed plumber and electrician to complete the job. It sounded dubious, but since their proposal only said to install the heat pump and water heater and nothing about attaching those to the existing system, I ended up doing that myself. It means they would be off the hook for protecting the existing water system from any contamination from their system if that is required. It never occurred to me to ask if they did complete hook up. Not sure if that meant that none of their technicians where licensed to do the work, but they had no problem running electrical to their heat pump. I’ve been the construction field all my life, and I’ve had almost universal good experience with HVAC contractors, so this was a first for me. Sure, they sometimes get behind schedule, but most all strive to provide the best service.


  • mikestooneat
    mikestooneat Member Posts: 11
    From you drawings you will need two . One as located in first drawing and one as located in second drawing.
  • Jamie Hall
    Jamie Hall Member Posts: 18,924
    You have to have one at location A in the second drawing. I'm honestly not sure about location B; if I were the inspector I wouldn't require one there. but the point is debatable.

    If they do require one there, or if there is a pressure reducing valve on the house service line, you must have an expansion tank on the hot water line to the house.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • SeanBeans
    SeanBeans Member Posts: 487
    If you put one in location B, is there a place nearby you can drain it if it happens to drain out? Some places may require a floor drain or sump pump near the building backflow. I’m not sure about residential but a lot of the multi family buildings here in Denver require both, including a sump pump and/or floor drain.
    delta T