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Backflow preventer with vent

Ron Jr.Ron Jr. Member Posts: 527
I know many towns around here require the backflow to have a vent . But why ? You'd think the built in check in a pressure reducer and a ventless backflow would be more than enough on a typical residential boiler . After having one with a vent flood someones finished basement , I think all BFPs with a vent are an accident waiting to happen .


  • icesailoricesailor Member Posts: 7,265

    If there is a leak through the back-flow, like it is leaking out of the boiler, it is supposed to leak out of the vent hold. The instructions, like T&PR valves say to pipe the overflow to a safe location.

    There was a discussion here of on another forum where the discussion was that you aren't supposed to leave the fill valve to a boiler open, that it should be left off. That came from B&G. That they won't be responsible for water damage if a fill valve is left open.
  • STMFTR420STMFTR420 Member Posts: 1

    Depends on which type is required, a RPZ style maybe required by the local authority, so a vent relief is a part of the device and needed, also the local authority might need a DC with vent just because there is no way to test them other than finding water from the vent.

    You would need to speak to the code enforcement officer to see if there are any alternatives for you to use.

    Remember this is a life safety device, any deviation could result in illness or fatality.
    Ok, but it's gonna cost ya!
  • Ron Jr.Ron Jr. Member Posts: 527
    edited March 2013
    Life safety device

    With what I see coating domestic pipes in some towns around here , I'd rather be drinking boiler water ! :)

    It's overkill for a vented backflow on these residential boilers , plain and simple . 3 separate failures have to happen for boiler water to back into the domestic ..........

    1 - pressure on the domestic side has to go lower than the boiler side .

    2 - the check in the pressure reducer has to fail .

    3 - the double check in the ventless backflow preventer we use has to fail .

    Chances of all 3 happening are nil . And most homes around here have no easy way to pipe these vents to a safe location . I'm all for safety but some codes just don't make sense considering the potential damage that can be done with an unnecessary relief line . And we all know how often these things vent out water .......
  • Charlie from wmassCharlie from wmass Member Posts: 3,922
    It has happened

    That's why we have the code. People have gotten sick and died, as we know code is often written in blood. When I was learning Mass code I I was taught the times and places I have forgotten those details by now though.
    Cost is what you spend , value is what you get.

    cell # 413-841-6726
  • RobGRobG Member Posts: 1,850

    I agree with Charlie. If someone plugs a leaking relief valve (we've all seen or heard of it) a couple of things could happen, If the system supply is shut off the person has created a bomb. If the supply is open and a non-RPZ installed the back pressure can blow the checks and start using the potable side as the expansion tank. It's rare, but not unheard of. To quote Steamhead "you can't fix stupid".

  • Ron Jr.Ron Jr. Member Posts: 527
    People have gotten sick and died ?

    From a system that had a backflow preventer and a pressure reducer ? 
  • Robert O'BrienRobert O'Brien Member Posts: 2,938
    i never saw

    I never saw a BFP on a residential boiler until 1999 and I've never heard of someone getting sick,much less dying in all those years before that!
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  • Ron Jr.Ron Jr. Member Posts: 527
    Haven't seen a BFP or LWCO on any water boiler

    up to maybe 10 years or so ago when we started installing them on everything . With the exception of the Blueray .

    Bob and I work where there is arguably more residential boilers per square than anywhere in the country . I never heard of someone getting sick or dying from boiler water poisoning .

    And to tell you the truth , how could you possibly diagnose boiler water as the culprit ?
  • Charlie from wmassCharlie from wmass Member Posts: 3,922
    The issue started with antifreeze

    poisoning from hot water systems. Vented BFP are required here for all hot water boilers that are hard piped to the potable water and for steam boilers that are connected with automatic feed valves. We are taking over 20 years ago when I was taught about the specific cases so it may take me a bit to find them in writing. With steam boilers there is the chance of live steam coming out the potable water faucets if a backflow occurs with no water pressure and the boiler producing steam. Think of this, if that basement had not flooded the people may have been drinking that water. Also since it was a failure of a plumbing part then it is usually covered by the home owners insurance.
    Cost is what you spend , value is what you get.

    cell # 413-841-6726
  • Ron Jr.Ron Jr. Member Posts: 527

    It wasn't a basement that got flooded . It was their living room , kitchen , hallway and a bedroom . All on the first floor of a slab house .

    And the vented backflow preventer failed . The fill was left on , the street side pressure never went lower than the boiler side . It vented and kept going . Dumping water from the domestic , not the boiler . The PRV stopped boiler water from backing out .

    I'm all for safety . I just think a vented backflow on residential systems are ridiculous when a double check , ventless backflow works just as well . And no potential for catastrophic damage .
  • Charlie from wmassCharlie from wmass Member Posts: 3,922
    Ron two questions

    Why was the vent not piped to a drain or a safe location where spillage could be seen but cause limited issues? We use catch pans and drains for any system not in unfinished space.

    Why did no one shut off the valves when they saw the water leaking?

    one reason vented BFP are used is they let you know a bad condition is occurring so you can address it.
    Cost is what you spend , value is what you get.

    cell # 413-841-6726
  • Ron Jr.Ron Jr. Member Posts: 527
    Charlie , I don't know

    why there was so much damage . Maybe the homeowners were at work . Maybe they were sleeping . Doesn't take too long to flood a slab house .

    The boiler is under the stairs in the middle of the home . No drain in the immediate vicinity . I guess you can concievably tap into a drain line down a nearby plumbing wall . If you want to rip open the kitchen or the bathroom and spend half a day ( and half a day's expense ) running the drain line .

    Like I said , it's ridiculous to require a vented backflow on a system that has 15 gallons of water in it . It's beyond overkill when every boiler we install has a pressure reducer AND a double check ventless backflow . The code needs to be changed . And when this crap keeps happening and people really start complaining and suing everyone involved , something might just happen ....
  • Charlie from wmassCharlie from wmass Member Posts: 3,922
    Ron I respectfully disagree

    I think a flooded house is much better than a sick person.
    Cost is what you spend , value is what you get.

    cell # 413-841-6726
  • Ron Jr.Ron Jr. Member Posts: 527
    You think

    a vented backflow is that much safer than a ventless ? 

    I will have to respectfully say no .

    And i will have to respectfully state that the chances of boiler water backing out of a system that has a PRV and ventless BFP are nil .
  • Charlie from wmassCharlie from wmass Member Posts: 3,922
    Yes I know they are safer

    I have seen many checks and double checks fail to prevent reverse flow. The vent does get peoples attention most times.
    Cost is what you spend , value is what you get.

    cell # 413-841-6726
  • Jamie HallJamie Hall Member Posts: 6,701
    Back 40 years ago

    when I was pretending to be a building inspector, we required vented RPZ backflow preventers or an air gap (depending on the application, obviously -- there are some things you just can't air gap!) on...

    residential hot water and steam boilers

    soda machines


    washing machines

    hose bibbs

    and a whole slew of other things.  Generally, anything which either did or could contain chemicals you might not like (such as antifreeze) or which did or could have low pH (like soda machines).  My recollection is that it was National Plumbing Code at the time -- and that we made ourselves very unpopular in some circles by doing it.  Which didn't change our minds...

    so the requirement has been around for quite some time, at least in some locations!

    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England.

    Hoffman Equipped System (all original except boiler), Weil-McClain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
  • icesailoricesailor Member Posts: 7,265
    Jamie's Correct:

    Jamie's correct.

    And you guys better get over it whether you like it or not.

    EPA now requires check valves on all new water systems to stop potable water from an unknown source from backing out of dwellings and into municipal potable water systems.

    During times of storms or flooding, when power is lost, there may not be enough pressure  to keep the pressure up in a public water system. When the Government started funding sewer treatment plants, they funded water supply systems too because it was cheaper to run sewer and water at the same time in the same trenches. Some of these areas were prone to flooding and other natural disasters.

    History then showed that with a lack of pumping power, potable water system couldn't be maintained and cross connections developed thereby contaminating the systems through sewerage that couldn't removed.

    Now you need expansion devices on water services inside buildings. I find heating system on occasion that have ethylene glycol inside. A small amount of that will kill a person.

    The house could have had no BFD, the fill valve on and a flooded house from a stuck relief valve.
  • Ron Jr.Ron Jr. Member Posts: 527
    edited March 2013
    You guys better get over what ?

    Not sure exactly what you mean with that statement ...........

    And I highly doubt you're reading fully what I've been saying in this thread . I'm not advocating doing away with backflow prevention .

    We use a pressure reducer valve and a ventless backflow preventer on every boiler install . You have a better chance of being hit by lightning , twice , then having water back out of a system with these 2 devices . A vented backflow is a pointless extra that has the pontential of doing major damage to a home .

    Thank you for the history lesson in cross contamination Ice . But how does it pertain to my post ? Is there irrefutable proof of  boiler water backing into any municipal water supply from any system that had a prv and ventless bfp ? Any links ? Or are we going by heresay ? ........  I'm all ears ......... :)
  • Ron Jr.Ron Jr. Member Posts: 527
    When you say

    you've seen MANY checks fail to prevent reverse flow , how exactly did you observe this ?

    Did you observe ventless backflows behave this way also ? If it's a matter of testing ventless backflows , it's fairly simple . Just shut the boiler fill valve and crack open the union on the inlet side and see what happens ..........

     I have never seen a backflow fail and let water flow in reverse to the street side . I've seen MANY fail by dumping street water through the vent , while the boiler water stayed where it's supposed to . 
  • Jamie HallJamie Hall Member Posts: 6,701
    The point, Ron

    is not that there is some sort of "proof" that the type of arrangement which you advocating is, or might be, unsafe.

    The point is that there is no way that I know of -- or knew of at the time -- to check an RPZ which does not have a vent.  If an RPZ vent is dripping, it's toast -- but it still is preventing backflow.  I've seen them.  Yes, I agree that if a vented RPZ fails in certain ways, somebody is going to get wet.  Sometimes even very wet.  That is unfortunate -- but it is rare for an RPZ to fail catastrophically.  The few I've seen failed drip for a while, and hopefully someone is paying attention.

    The possibility of a failed RPZ which retains an intact connection to a contaminated water source, however, can affect a number of people, not just one building.  There is, for example, an area in a town near where I live where the public water supply pressure more or less routinely drops below atmospheric.  Yes, I know it shouldn't, obviously, but that's a different problem.  If someone in that area has ethylene glycol in their heating system, or a chromium based antioxidant in their boiler water, or is spraying a nice pesticide, and the pressure drops and there is no backflow prevention... did I mention that there is an elementary school in this area, as well as about a hundred houses?

    Anyway -- it is or was code.  Tell them to check the vent from time to time...

    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England.

    Hoffman Equipped System (all original except boiler), Weil-McClain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
  • Ron Jr.Ron Jr. Member Posts: 527
    Jamie , you are missing my point

    All along I was talking about residential homes with water content much , much lower than any commercial building . And or course I agree with you that anything commercial must have a vented backflow . The chances of chemicals and much more water backing out than a residential boiler are well worth the chance of the vent leaking .

    I am well aware of the consequences of what CAN happen when boiler water backs out of a system , so thank you for sharing .

    I will say this once again . I do believe every residential boiler should have a backflow preventer . And I know the chances of a pressure reducing valve AND a ventless backflow preventer both failing is in the range of zero . I truly believe a vented backflow is past the point of overkill in residential homes when you have 3 checks ..... ......1 in the prv and 2 in the ventless .  I know for a fact a fraction of boilers in the Long Island area have backflow prevention .  Not once have I heard of cross contamination . Not saying it's right , just saying it's not heard of . And FYI , backflow testing on residential homes here is not required . And in the homes that do have a vented backflow , you'd be amazed how many have a plug where the vent is supposed to be .......    ( after inspection I would assume ) .
  • Charlie from wmassCharlie from wmass Member Posts: 3,922
    One sick child

    Have you seen a truck loose it's brakes on a long hill and crash? They build run away truck ramps yet it hardly ever happens. One sick child, one dead person, these are not worth a hundred flooded houses. Do you not think that we have few cases because of the codes we have?
    Cost is what you spend , value is what you get.

    cell # 413-841-6726
  • icesailoricesailor Member Posts: 7,265
    Checks in PRV's:

    Because I always replace them, and a RPZ Backflow is required, I have changed more PRV's with defective checks than I can remember or count.

    But I have also seen more improperly installed RPZ backflows than I can count. That was before Watts started selling Combi units, 9-11S's. "Heaters" that connected the potable water to boilers would usually install the backflow AFTER the PRV/1156F there it belongs BEFORE the PRV/1156. In Massachusetts, the code stops at the backflow. What ever happens after the Backflow is of no consequence. After the backflow, it isn't a plumbing code issue. If you don't like backflows, present it to code writing officials and AHJ's. Until then, install LWCO's and shut off the fills.

    I remember a huge discussion here back a while ago about leaving fill valves open or closed. B&G said to absolutely leave them closed because they would not be legally liable  for a failed back flow and subsequent damage.

    You still need a backflow.

    Also, you can't buy Cast Iron Watts S1156F's any more. Especially as 9-11F Combi's. The cast iron would crud up the SS screen and block the flow. I'm convinced  that Watts quietly eliminated them because of the clogging problem. I saw quite a few boiler failures because of PRV's not filling a leaking boiler and them turning into a steam pot. Brass ones used to be very expensive and suddenly, you couldn't get the cast iron ones, there was no change in number, and brass was the only ones you can get. At the same price as the old cast iron ones.

    With the new "No-Lead.Brass" rules, will we now have plastic backflows? Remember, the plumbing code stops at the backflow.
  • icesailoricesailor Member Posts: 7,265
    Cross Connection Contamination:

    Just because no one appears ill, doesn't mean that someone isn't exposed.

    Where I work, the wealthiest needed to have trophy landscaping to go with their trophy homes. Irrigation companies started up to provide water to make this happen. They decided that it was legal for them to connect to the potable water systems for their water. No code, permits or inspections. Some had heads above the C/L of the backflow's  but at least they had backflows. They would install a boiler drain so they could winterize the systems by blowing compressed air into the systems. Some of their installers put the drain BEFORE the backflow. On more than one occasion, the blow out crew connected the air hose to one of these wrongly placed connections, shut off the backflow and turned off the air. After a 1/2 hour or so with no pressure in the irrigation system, someone discovered that they had pumped hundreds of cubic feet of high pressure air into the municipal water system. You should see what can happen in a house next door.
  • billtwocasebilltwocase Member Posts: 2,385

    I too have seen too many fail as Ron is talking about. It's the vacuum relief side that is failing, not water flowing in the wrong direction. There is one that is notorious, and 9D comes to mind. Years ago here, a simple check valve was the norm, then someone suggested breaking the vacuum in the domestic. I see where Charlie is coming from too, but that is not what Ron is talking about. The vacuum side is what's failing, so why not be able to go back to a check valve and separate vacuum breaker? There is, or should be one in the home if there is a water heater.
  • Ron Jr.Ron Jr. Member Posts: 527
    One sick child ?

    No need to get melodramatic . Of course I don't want to see a child get sick from cross contamination .

    But " thinking " we have cases of cross contamination with a prv and backflow .......  and it actually being the truth are 2 separate things . Your runaway truck analogy really isn't the same issue . We KNOW truck brakes fail and we know what happens when they do . Do we have a true case of cross contamination from the setup in question ?
  • HillyHilly Member Posts: 368
    too important not to have

    Has anyone posting on this topic become AWWA certified for backflow prevention testing? These items do 'FAIL' and that is why they require annual testing forever. If there is anything feeding the system other than potable water then the BF device has to be RP (or RPZ as some have referred to them) I remember my plumbing instructor telling us about going to a house call in the '80s where the lady complain the tap water was a greenish colour. Not to mention the countless ones we hear about from the AWWA course agenda.

    Also if there is a drip on the RP's vent that doesn't mean it is failed completely. There are multiple security measures put into these devices, a drip on the vent could mean the relief port opened for an acceptable reason and is in need of repair. And even if that is failing and the most downstream check is failing, it doesn't mean that the most upstream check isn't still functioning 100% and protecting the household and municipal supply from contaminations.
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