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Louisiana code for Backflow preventer on solar hot water systems

michael_34 Member Posts: 304
I have been talking with a gentlemen in New Orleans about solar thermal. He is having problems selling the systems because the Dept. of health demands that a backflow preventer is put on the main water line coming into the house, thus creating a higher cost to the customer.

I understand why back flow preventers are put on residential and commercial water systems, (kind of, I don't understand where contamination would come from) But why, on a solar thermal system would you need a backflow preventer on the main water system coming into the house?

Here is a link about the Louisiana code:<a href="http://www.lses.org/problems-heating-up-for-solar-water-heater-installations-in-la/">http://www.lses.org/problems-heating-up-for-solar-water-heater-installations-in-la/</a>




  • hot_rod
    hot_rod Member Posts: 22,505
    the intent

    is to prevent any heat transfersolar fluid from getting into the public water supply.

    With an approved, non toxic solar fluid there should be no concern.

    The potential for an installer to use automotive, EG or even some heat transfer oils does exisit, which causes some AHJs to error on the safe side.

    The same goes for double walled heat exchangers that some codes still require and enforce.

    Always label your solar systems with a tag, or mark right on the tank,  to indicate the fluid you used.  This helps the inspectors as well as any future service tech.  I believe the SRCC OG-300 (operating guideline) requires that label.

    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • michael_34
    michael_34 Member Posts: 304
    edited September 2011
    Thanks HR


    My only response regarding the DHH letter pertaining to the backflow preventer issue is that it is absurd at best. What contaminants are they protecting against? If all direct systems are outlawed by the DHH, subsequently all systems will have a heat exchanger (double walled, yikes!). I do not know the failure rates of heat exchangers, but I have seen some in solar and boiler systems that are well over 20 years old. The heat exchanger may have lost efficiencies, but still had containment.

    The backflow preventer is the tip of the iceberg in the DHH requirements. The outlaw of direct open loops mystifies me. It's the city, states water supply that is being used. The only contaminants that are in the water, they have put in (sodium fluoride, chlorine and other heavy metals). If they are so worried about the potential of the HTF from a solar system contaminating the potable water supply, then only allow water and propylene glycol to be used as the HTF. Outlaw the use of ethylene glycol as a HTF.

    I know some states and cities municipalities require a backflow preventer on all new construction. And I still do not understand that, but to penalize one small certain area of water connection (solar in this case) is misguided

    I guess it our jobs to educate the folks that make the rules.

    Thanks again HR

  • VJW
    VJW Member Posts: 1
    Codes in other jurisdictions

    I haven't seen the specifics of the Louisiana code, but I am pretty aware of the International Plumbing Code and the Uniform Plumbing Code, which blanket most of the U.S.. Here's how they deal with this:

    The Uniform Plumbing Code (UPC) is the most stringent. It specifies that a double-walled heat exchanger is required for systems that utilize a nontoxic heat transfer fluid with a pressure relief valve rated higher than 30psi. There is an extremely gray area in "Engineered Systems" that allows the PRV to be rated below the minimum potable pressure (in a well system, this is realistically 0psi). Oregon was granted an exception to this portion of the code (here's the explanation they gave to the board: http://www.cbs.state.or.us/bcd/boards/plumbing/boardpack/08/20081017/Plumb_101708_VIIc.pdf), allowing adherence that is more representative of the International Plumbing Code (IPC).

    The IPC allows a single wall heat exchanger as long as the HTF is nontoxic. It's pretty cut and dry.

    I would suspect that the LA code has some basis in one of these codes (or maybe the NSPC). If so, hopefully they can figure out a way to protect their clients while maintaining affordability.

    Why can't they put in a Watts 7U-2, which runs $45 or so and is pretty low-profile? (http://www.pexsupply.com/Watts-0061791-3-4-7U2-2-Dual-Check-Valve-5461000-p). Of course, this will require a thermal expansion tank at the water heater (if it isn't already required).
  • michael_34
    michael_34 Member Posts: 304
    edited October 2011
    Good info

    Thanks for the info.

    I am actually down In Louisiana now to help them rectify these codes and spread some light on SWH systems.
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