Question regarding check valve in water-feed line

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Old 05-02-11, 12:33 PM
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Question regarding check valve in water-feed line

Hi all,
Need some help here. Pointers. Would appreciate any feedback.

Have a boiler installation. The issue I need help with is the Automatic feed line.
This line has installed (in the order mentioned next) a ball valve, followed by a Watts-9DM3 (backflow preventer), then by Watts-1156F (feed water pressure regulator), finally by a second ball valve. There sure is also a bypass line with a ball valve for quick fill.

At any rate, the local building inspector is asking that a check valve be installed downstream from the Watts-1156F valve.

The issue is: the 9DM3 backflow preventer already has 2 check valves incorporated in it.
Why do we need another check valve? Where can I find the appropriate code page(s) that state(s) the need for this additional check valve?

Thanks in advance for any light any of you could bring to the table in this regard.
 
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Old 05-02-11, 01:22 PM
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Maybe it's the bypass line that adds the requirement for an additional backflow preventer. Have you asked the inspector why he wants another one?
 
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Old 05-02-11, 01:54 PM
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Some township codes do not recognize the 9D as a check valve. I think its actally a dual check. I will try to find the code for you. I think its a township thing though.

Mike NJ
 
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Old 05-02-11, 03:45 PM
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it needs to be a metal seated swing check downstream of feeder and backflow. make sure you put it between the iso valve and the feeder in case you need to replace it without disturbing the system
 
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Old 05-02-11, 03:49 PM
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RDSTEAM isnt the 9D actually a better check valve the a metal swing check? My old boss always argued with the inspectors on this. ( probably why he failed insections so often)

Mike NJ
 
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Old 05-02-11, 04:22 PM
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I think Droops might be onto something here...

The fast fill bypass you mentioned; where is is located in relation to the other components?

I'm betting that you've got the 'combo' unit, 9D and 1156 combined with a close nipple between them, and your bypass line spans them both, right?

Let's use the scenario of the domestic water pressure failing... if someone opened that ball valve on the bypass, would the 9D protect from backflow? If so, maybe the inspector would be satisfied if you moved the tee for the fast fill bypass between the 1156 and the 9D.

I can't imagine any town not accepting the 9D. After all, it's designed with the atmospheric vent so that you KNOW if one of the other checks is leaking! You will see water coming out the vent! With a standard metal swing check, you wouldn't have a clue.

Why do you even need the fill bypass? The 1156 has a fast fill included.

There is also a check valve in the 1156 I believe.

Paul, is this a 'pop quiz'? Did we pass?
 
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Old 05-02-11, 06:13 PM
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the photo trooper requested

Everybody: Thank you kindly for your time. It's nice to be back. I haven't posted in a looong time. Below is the photo trooper requested. I hope it gives more light and helps solve the mistery of the inspector's request. BTW, I was not at the site when he came. All I got was a short list of things he wanted done. This being one of them

Trooper: great seeing you're still around!

Gang: I'm more knowledgeable with air systems. I can handle boilers, but when it comes down to the little details at times I get stuck wondering "why"...just like this time.

 
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Old 05-02-11, 06:16 PM
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code book on boilers

I would love to be able to put my hands on a copy of the code. Where can I buy it? an electronic version is perhaps available? My interest is specifically on the code as it applies to boilers and boiler installation requirements.

Thanks!
 
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Old 05-02-11, 06:39 PM
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The bypass is the problem, I'd just get rid of it. As Trooper states, the pressure regulating valve has a "fast fill" feature so the bypass is just more plumbing. If that bypass valve were to leak even slightly there could be a backflow under some (admittedly remote) conditions.

As for the "boiler code" there really isn't one. Codes are suggestions and have no force of law UNTIL adopted by the local or regional governmental body having jurisdiction in your area. These governmental bodies generally have some committee, group or agency to promulgate the regulations and these generally adopt a model code BUT they may add to or delete from the model code. What this means is that what is allowed and what is prohibited is a matter of local or regional law and therefore it is impossible for someone on this board to make any absolute statement as to what is allowable or prohibited. Your local code may be on available on-line or it may be available for purchase. Local libraries may also have the local code available.
 
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Old 05-02-11, 07:48 PM
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This is what I got from the code. I bet if you remove the by-pass you will still fail.

Section IV HG-705

The makeup water pipe shall be provided with a check valve near
the boiler and a stop valve between the check valve and
the boiler or between the check valve and the piping system.


In lieu of a check valve in the makeup water line, a back flow
preventive device may be used if it meets the requirements
established by the Boiler Regulation Advisory on Backflow
Preventers issued by the BB&PVC. (Bureau of Boiler and Pressure Vessel Compliance )


And this is from the BB&PVC

The BB&PVC has determined that a standard
backflow preventer, as required by the Plumbing Subcode,
would not prevent the backflow of water from a boiler into
the potable water system due to the fact that the seats on
the backflow preventer check valves would not be able to
withstand the high-temperature hot water from the boiler
should there be a break in the water supply system which
would cause a back siphonage from the boiler into the
potable water system. Typically, backflow preventers are
rated at 140 degrees to 180 degrees Fahrenheit. Check
valves are rated at 250 degrees Fahrenheit. The ratings
of the backflow preventers and check valves were verified
through the manufacturer of the devices.
Also, with the use of a reduced-pressure backflow
preventer assembly, should the check valve in the backflow
preventer fail due to the high-temperature water backflow
from the boiler, the backflow would discharge through the
relief vent, which puts the boiler at risk for a dry-firing
condition and could result in a catastrophic failure or a
boiler explosion. This would also apply to a double check
valve assembly should the assembly check valves fail due
to the high-temperature water which would backflow into
the potable water supply.

Mike NJ
 
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Old 05-03-11, 06:29 AM
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That's interesting. My question is how much water would flow back from the boiler towards the domestic supply before the checks close and stop the flow? I would think it happens fairly quickly, and, at least in my setup, the makeup water line doesn't get hot. I wonder if this is just theoretical or it has been seen in the field. If this municipality is that up to date with their codes, you would think the require a LWCO. If the do, I would think that would would take care of such a situation. Back flow preventers aren't new, right? I would think they function for what they were designed for.
 
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Old 05-03-11, 07:07 AM
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you would think they require a LWCO
It should have LWCO. All boilers after 2001. I believe thats when the code changed.

Also I am with Trooper and Furd. Since you have to take all that apart to add the check I would remove the by-pass.

Mike NJ
 
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Old 05-03-11, 08:59 AM
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Mike is correct about the temp ratings being the requirement for the check valve. Some parts of the backflow preventer are plastic which could distort in the presence of very hot water allowing reverse flow. I read a more elaborate explanation of this several years ago.
 
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Old 05-03-11, 09:57 AM
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I know you cant win with the inspectors but the watts 9D m3 and m2 is rated at 250F. Is it worth the argument?

http://media.wattswater.com/ES-9DM3_M2.pdf

I guess this is what you need.

Stainless Steel Swing Check Valve (T-750) - Check Valve made by Legend Valve

Mike
 
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Old 05-03-11, 02:41 PM
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im pretty sure its code in nj now, because we went on a check valve tear about a year and a half ago. had to put thse suckers in EVERYWHERE!!! it was commercial accounts though. not sure if its mandatory in residential.
 
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Old 05-03-11, 02:43 PM
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the boiler does have a Guard Dog LWCO, and at least one of the two built-in Watts dual check valves have plastic seats (as per specs)...don't quite remember the material for the second one.

Thanks to all. I have enough ammunition from the threads you kindly shared here.
 
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