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Non-toxic water inhibitor for closed loop DHW system?

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davidd
davidd Member Posts: 84
I have a ModCon boiler and an indirect water heater (single walled coil). It has always been in the back of my mind that I'm would end up with treated water making its way into the potable water if the coil in the indirect water heater develops a leak.

I've been using the Rhomar 922 inhibitor. I can't find any information on whether it is considered toxic if it makes its way into the potable water. Is there a list somewhere of inhibitors that are safe for aluminum heat exchangers and safe if they end up in the potable water supply?

Thanks,
David

Comments

  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 8,167
    edited March 2023
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    Under normal operation the DHW pressure will migrate into the treated boiler water. That is because the open system DHW is at a higher pressure (35 PSI to as much as 80 PSI) than the closed loop water pressure (Less than 30 PSI on most residential systems) So I would not worry about that. The only time there may be a problem is if you develop a coil leak at the same time that you loose potable water pressure. Then you would not know about the leaking coil and you could get some reverse migration from the treated 12 PSI boiler water into the potable water @ zero pressure water in the tank.

    What is more likely is the potable water pressure from the tank coil leak will push the over 35 PSI pressure into the boiler water causing the 30 PSI relief valve to blow off regularly.

    Mr. ED

    Edward Young Retired

    After you make that expensive repair and you still have the same problem, What will you check next?

    GGross
  • davidd
    davidd Member Posts: 84
    edited March 2023
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    @EdTheHeaterMan ,

    Thanks for the reply. My concern was that the leak could be present and unnoticed, and then if the well pump were to fail without us knowing, the potable water pressure could go to less than the boiler loop pressure, and we could be drinking some of the boiler water.

    However, I didn't think through about the fact that it would blow the pressure relief valve on the boiler loop. That's my way for this to not go unnoticed. I'll set up a sensor and alarm system on the pressure relief valve (which is good to have regardless).

    I'd think that if a leak happens, not only will the pressure relief valve blow once, it will continue to blow, because the well pump will not switch off until it has filled the well pressure tank. And the well pressure tank can't reach full if a gusher is occuring at the boiler relief valve.

    All this is hypothetical, and I'm guessing I won't see it happen in my lifetime. However, by putting an alarm on it, I'll not only be notified if a leak develops in the indirect water heater coil — I'll also be notified if the pressure relief valve gets week and blows at a lower pressure than it should.

    I really appreciate you walking through all that and pointing me in the direction of the pressure relief valve. Thanks!

  • hot_rod
    hot_rod Member Posts: 22,476
    edited March 2023
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    I have seen pink colored water come out of a faucet of a failed indirect on a glycolled boiler. So there could be some contamination. That is why codes sometimes require double walled HX when using fluids like ethylene glycols.


    Good question about the conditioners. I don't know if they get scrutinized like glycols by the FDA.

    GRAS is one term used, generally regarded as safe. By whom🤓


    should be a SDS sheet with the product, what does it say?

    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • kcopp
    kcopp Member Posts: 4,448
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    nother option to adding an inhibtor would be flush your system out and fill w/ a demineralized water. I have done a number of systems w/ the Axiom filter and it is great. Takes most all the nasties out of the water.

    In the UK they are now pushing this water standard (may even be maditory)

    https://axiomind.com/axiom_products_cat/h2o-demineralizer/

  • hot_rod
    hot_rod Member Posts: 22,476
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    I agree on DI water. I'd check occasionally for magnetite which would indicate oxygen is getting in.

    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • davidd
    davidd Member Posts: 84
    edited March 2023
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    My boiler has an aluminum heat exchanger. I don't think I'm going to be able to avoid an inhibitor.

    Does that pink water taste like bubble gum? 😀

    Generally regarded as safe by anyone not drinking that water!

    I thought I looked at the MSDS sheet, but I could be getting confused with something else. I'll check it out and report back later.

  • hot_rod
    hot_rod Member Posts: 22,476
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    some aluminum boiler ship with a conditioner, tells you how important it is.

    Blending it with crappy water pretty much destroys some of that conditioner package, however.

    Clean the system, fill with good water, add aluminum conditioner


    The warranty probably addresses water quality and treatment?

    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • davidd
    davidd Member Posts: 84
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    I've only used distilled water in the boiler, from day 1. And I ensured the pH was correct, as per the manual. However, the correct pH for aluminim is a lot lower than for iron, so there is that to consider.

    The Rhomar products are listed in the Buderus manual as supported.

    I don't remember if the warranty talks about water quality, but it is past the warranty period. I just figured since I was going to be doing a full flush and clean on the system, and a full load of fresh water, with inhibitor, I'd see if anyone knew about the safety of the inhibitor, should it sneak into our water supply.

    Some information from the MSDS for the 922 product:

    ...

    SECTION 5 – HEALTH HAZARD DATA
    PRIMARY ROUTES OF ENTRY ( ) INHALATION ( ) INGESTION ( ) SKIN ABSORPTION ( ) EYE ( X ) NOT HAZARDOUS
    ACUTE EFFECTS:
    INHALATION: Not likely – no adverse effects.
    EYE CONTACT: May cause slight irritation. SKIN CONTACT: None
    INGESTION: May cause gastrointestinal irritation.
    CHRONIC EFFECTS: None known.
    Medical Conditions Generally Aggravated by Exposure: None identified.

    ...

    ...

    EMERGENCY FIRST AID PROCEDURES
    Eye Contact: Irrigate with water for 15 minutes.
    Skin Contact: Wash off and rinse thoroughly with water.
    Inhalation: Move to fresh air.
    Ingestion: DO NOT INDUCE VOMITING. Drink 3-4 glasses of water. Get immediate medical attention.

    ...

    ...

    ORAL TOXICITY: Gosselin- 1, LD50 (oral rat)
    Hodge and Sterner – 6, LD50 (oral rat

    ...

    Typically LD50 values are given in mg/kg. If this is 1 mg/kg or 6 mg/kg, I certainly wouldn't want to be drinking it if I was a rat. For comparison, household bleach has an LD50 of over 8,000 mg/kg. Having said that, it would be highly diluted in the boiler water.

  • kcopp
    kcopp Member Posts: 4,448
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    If you dont belive me here is a european comany.

    https://elysator.com/wp-content/uploads/brochureSorbox_en.pdf

  • davidd
    davidd Member Posts: 84
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    Those look like a nice addition for people who use tap water. But are you saying they somehow provide the same corrosion inhibition to aluminum heat exchangers that inhibitors do?

    In my particular case, I'm not concerned about lime and chlorine, since I only use distilled water. The inhibitor helps to bring the pH to appropriate levels too, since distilled water, when exposed to air, becomes slightly acidic. I'm fortunate, since my closed loop is relatively small. With my hydronic coil in the air handler, I don't have piping around the house to emitters. It seemed like a no brainer to me to use the distilled water instead of dumping our well water into the system. We do have a water softener, but I wouldn't have been following the boiler recommendations by using salt softened water.

    So for my particular situation, a magnetic direct separator seems like the better approach, rather than a water demineralizer.

  • hot_rod
    hot_rod Member Posts: 22,476
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    I think the ph range is tight for aluminum regardless of glycol or conditioners. Get a small ph stick meter and test yearly. It's easy to adjust ph up or down on a small capacity system


    For your small capacity system a Sorbox may be overkill. Good fill water, DI or distilled, a ph balance, and a conditioner specific to aluminum


    Water quality gets a bit more complicated with all the different metals in a system. The conditioners get expensive when they blend so many different ingredients for aluminum / multi metal systems


    with a Caleffi DirtMag you get an excellent dirt and partial separator and the magnet

    Other brands offer good mag separation but not always particle seperation

    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • davidd
    davidd Member Posts: 84
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    @hot_rod,

    What do you recommend as a pH adjuster. I've just used the Rhomar 922 to adjust it, but that's not a fast adjustment.

    When looking for more literature on 922, I came across this article. Seemed timely on multiple fronts. 😀

    https://www.phcppros.com/articles/12745-no-more-dirty-water

  • hot_rod
    hot_rod Member Posts: 22,476
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    you can get ph

    adjusters from the hydronic conditioner suppliers. Probably some quart sized containers would last you years.


    I suspect these are not far off of the pool chemical ph up or down? Soda ash or acid?

    May be some additional ingredients in the hydronic specific adjusters

    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • davidd
    davidd Member Posts: 84
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    I found the Rhomar pH boost after sending that last message. I've been relying on the pH buffering in the 922 solution, but it just takes more time to raise the pH. The buffering is good, but it would be nice to be able to make a fast adjustment sometimes.

    I did look at the MSDS for the Rhomar boost product. It is only green food coloring, water, and caustic pot ash (potassium hydroxide).

    I too thought it might contain some special sauce. Doesn't appear like it does. That's in the 922 product.

  • hot_rod
    hot_rod Member Posts: 22,476
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    A small amount of 922 in the potable water? Maybe the same as drinking Dr Pepper, or diet soft drinks🤔

    Or and energy drink that are considered fluorescent colored battery acid, in the beverage industry.

    If it is enough of a concern, double walled HX are still available with a vented space to detect a leak.

    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • davidd
    davidd Member Posts: 84
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    Just to be clear, it is the Rhomar pH boost that has the potassium hydroxide in it. I doubt the small amount of that mixed in the boiler water and then mixed in the potable water would cause any major problems.

    The Rhomar 922, which was the original concern, has a confusing MSDS. The LD50 status look alarming, but that could simply be an omission of the units of measure.

    My indirect is single walled. SuperStor makes a double wall. I wasn't given that option by the installer and the topic didn't come up. I probably would have paid the extra for the double walled unit at that point in time, but I'm not concerned about it enough now to pay for a switch. By putting an alarm on the pressure relief valve of the closed loop, my family will be notified before anyone slurps down some inhibitor. 😝

    You mention vented spaces to detect a leak in a double walled unit. Does that mean a leak from one wall will fill up the space between them and leak out the top or bottom of the water heater?

    Thanks,

    David

  • hot_rod
    hot_rod Member Posts: 22,476
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    Here is what it looks like on a BPHX. On some indirect tanks there was a coating over the HX tube with a cord for the leak path, oput the top of the tank. The BradfordWhite CombiCors used that method. Some have a coil in a coil.

    There are a few areas in the country that still require double walled HX for potable water, Minneapolis I think is one? So some manufacturers still offer double walled indirect tanks.

    More cost and a bit lower performance with that space.

    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    fenkel
  • kcopp
    kcopp Member Posts: 4,448
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    Thats what i am saying. They have been doing it over there for years w/o issue.

  • davidd
    davidd Member Posts: 84
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    I guess the question would be whether they are doing it with aluminum heat exchangers or stainless steel.

  • davidd
    davidd Member Posts: 84
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    Thanks for the diagrams. Helps to visualize what is going on.

    Thanks for pointing out the topic of codes. I looked up the Minnesota codes. Here is what I found:

    603.5.4 Heat Exchangers. Heat exchangers used for heat transfer, heat recovery, or solar
    heating shall protect the potable water system from being contaminated by the heat-transfer
    medium.

    603.5.4.1 Single-Wall Heat Exchanger. Installation of a single-wall heat exchanger shall
    meet all of the following requirements:
    (1) Connected to:
    (a) a low-pressure hot water boiler limited to a maximum of 30 pounds-force per square
    inch gauge (psig) (207 kPa) by an approved safety or relief valve; or
    (b) a steam system limited to a maximum of 15 psig (103 kPa).
    (2) The heat-transfer medium is either potable water or contains fluids having a toxicity
    rating or Class of 1.

    (3) Bear a label with the word "Caution," followed by the following statements:
    (a) The heat-transfer medium shall be water or other nontoxic fluid having a toxicity
    rating or Class of 1 as listed in Clinical Toxicology of Commercial Products, 5th edition.
    (b) The pressure of the heat-transfer medium shall be limited to a maximum of 30 psig
    (207 kPa) by an approved safety or relief valve.
    The word "Caution" and the statements in letters shall have an uppercase height of
    not less than 0.120 inch (3.048 mm). The vertical spacing between lines of type shall
    be not less than 0.046 inch (1.168 mm). Lowercase letters shall be compatible with
    the uppercase letter size specifications.

    603.5.4.2 Double-Wall Heat Exchanger. Double-wall heat exchangers shall separate
    the potable water from the heat-transfer medium by providing a space between the two
    walls that are vented to the atmosphere.

    The bolded words are what this thread was all about. We still haven't determined if Rhomar 922 is a low enough toxicity so as to not worry about it. I'm not sure how to determine if it would have a toxicity rating of 1.

    The other night I was thinking about looking up the specs on the double walled SuperStor tanks vs the single walled. I assumed they'd either have a lower heat capacity or they'd upsize the coils to counter the inefficiencies.

    David

  • hot_rod
    hot_rod Member Posts: 22,476
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    give Rhomar a call? There are a few different groups and terminology use in describing toxicity of fluids.


    Possibly different interpretations?

    It comes down to what you are comfortable with

    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • davidd
    davidd Member Posts: 84
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    @hot_rod wrote:

    give Rhomar a call? There are a few different groups and terminology use in describing toxicity of fluids.

    That's probably the best course of action. I'll try to find time to do that during the work week.

    Thanks,

    David

  • hot_rod
    hot_rod Member Posts: 22,476
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    A few unknowns, how toxic is the product? How much would it be diluted if a HX fails?What's the odds of a failure?

    You can also run straight water, no conditioners. If so start with deionized water.

    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Derheatmeister
    Derheatmeister Member Posts: 1,572
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    You may want to read the German VDI 2035 or the None Chemical portion of the new ANSI H1001.1

    We have used this None Chemical approch for many years even on small residential applications in conjunction with Sacrificial anodes with Great results.

    We only had problems with a manufacturers Mixed Resin that shall remain unnamed .

  • davidd
    davidd Member Posts: 84
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    Thank you. What are the sacrificial anodes made out of when trying to protect an aluminum heat exchanger without adding chemical inhibitors? And how do you introduce the anode into the hydronic loop?