# Does (in code terms) a PRV substitute equally as replacement for a Dual Check Valve?



## DUNBAR PLUMBING (Sep 11, 2008)

Is it overkill to install a Pressure Reducing Valve AND and a Dual Check Valve in the same line? 


Or can the Dual Check be removed, the Pressure Reducing Valve installed in place of it.


Given that some homes are required Dual Checks by authorization of local backflow prevention programs. 


Is this a correct substitute. 

I understand most check valves are dual, but decipher where it reasons both devices on the same line.


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## plbgbiz (Aug 27, 2010)

Don't they serve two distinctly different purposes? How could a PRV serve as backflow prevention or how could a DC reduce pressure?


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## ILPlumber (Jun 17, 2008)

Is a PRV ASSE #1024? NO Your code is going to require a 1024 approved device.

There will be pressure drop over each check of a dual check valve. Maybe a total loss of 4 psi.....


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## Redwood (Sep 8, 2008)

Although a PRV does serve as a check valve in its operation, it acts as a single check, with in many cases an integral bypass, so it is not rated as a check valve for use in back flow prevention


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## ToUtahNow (Jul 19, 2008)

DUNBAR PLUMBING said:


> Is it overkill to install a Pressure Reducing Valve AND and a Dual Check Valve in the same line?
> 
> 
> Or can the Dual Check be removed, the Pressure Reducing Valve installed in place of it.
> ...


If you are installing a Reduced Pressure Principal Device at the same location as an existing dual check (way overkill) the dual check would be redundant (not needed).

Mark


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## ILPlumber (Jun 17, 2008)

ToUtahNow said:


> If you are installing a Reduced Pressure Principal Device at the same location as an existing dual check (way overkill) the dual check would be redundant (not needed).
> 
> Mark


I read it as PRV not RPZ..


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## Titan Plumbing (Oct 8, 2009)

I'm reading it as PRV and double check.........


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## ToUtahNow (Jul 19, 2008)

Matt said:


> I read it as PRV not RPZ..


You might be right I just couldn't figure out why they would be listed together.

Mark


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## ToUtahNow (Jul 19, 2008)

Choctaw said:


> I'm reading it as PRV and double check.........


But how is a dual check a double check?

Mark


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## Titan Plumbing (Oct 8, 2009)

A double check and a dual check both have two checks...that's all I can figure. Hell, IDK if you read the post before he edited it, it made even less sense.


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## ILPlumber (Jun 17, 2008)

A dual check is non-testable. They are required by MOST municipalities. Most are in the meter loop itself.

A double check is a testable device.


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## ToUtahNow (Jul 19, 2008)

Actually a Watts L7 is testable but I still consider all dual checks disposable.

Mark


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## ILPlumber (Jun 17, 2008)

I have never seen one of those in the field. Our cross connection program does not require the annual inspection of dual checks.

Mostly see the 7.


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## nhmaster3015 (Aug 5, 2008)

If you want to know why a PRV ain't a BFP just open it up and take a look at the check assembly.


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## DUNBAR PLUMBING (Sep 11, 2008)

I understand that never will a PRV be the suggestion of protection in backflow means, 


I'm saying if I enter a home, residential service, and a customer has high water pressure. 

Upon inspection I find a non-testable Wilkins 70 dual check valve assembly. Probably a requirement at the time of construction of the home.


Since I know, depending on what pressure reducing valve I install (thermal bypass not)...

is it mandatory to leave that dual check in, install the pressure reducing valve and now have 3 types of components (technically speaking) working as a check valve in that main line.

I have a customer that in order to put in the pressure reducing valve along with gauges to measure incoming and outgoing, the dual check valve's elimination makes easy work of the task. 

If no, then I have to build a myriad of piping that allows to work in such a small confined area, and it will be time consuming.

I'm all about doing it right, to code...but where this home is located, they didn't even require thermal expansion protection when the dual check was installed, which can create all kinds of issues above 60psi and 120 degree water from a heating device.

This would not be inspected, and rarely do I see the requirement for dual checks on residential applications, only commercial where slight degree hazard applies.

So....it was an overkill design, even though I truly agree it is warranted, given back at the time where there were no anti-siphon hose bibbs to speak of. 

At least they was thinking ahead of the game, and the neighborhood would be of the possibility where sprinkler systems would be a possibility. 

That usually dictates with income levels and housing costs usually.


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## GREENPLUM (Jul 27, 2008)

this poll is flawed 


im not voting,,,:laughing:


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## user4 (Jun 12, 2008)

ToUtahNow said:


> Actually a Watts L7 is testable but I still consider all dual checks disposable.
> 
> Mark



Chicago will not recognize that as a certifiable device because it lacks a port to isolate one check from the other for testing on both the inlet and outlet side.

As for the question in the poll, a PRV is not a backflow preventer, and can't be used as such, so it would really depend on what the local code is looking for as protection to the cities water main.


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## nhmaster3015 (Aug 5, 2008)

I suspect Dunby that you is gonna have to hack up the piping and get em both in the line. I sure do like the meter/bfp combo but only the new houses get them.


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## DUNBAR PLUMBING (Sep 11, 2008)

And I don't mind doing it that way...because I'll make more money as a result. I am going to replace that dual check with a new one while we are at it. Springs always break on them, or the rubbers wear out and the clanging begins when the water gets turned off and on.


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## Tommy plumber (Feb 19, 2010)

Matt said:


> A dual check is non-testable. They are required by MOST municipalities. Most are in the meter loop itself.
> 
> A double check is a testable device.


 
True Matt, in backflow class we were taught that RPZ's and DC's are required to be able to be tested and re-certified 'in-line'. Repaired also as you state. That is also why devices cannot be sold w/o (2) ball valves. Must be ball valves, not gates anymore.


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## plumber666 (Sep 19, 2010)

Back on topic, a PRV is in no way shape or form a check valve.


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## Pipe Rat (Apr 5, 2009)

plumber666 said:


> Back on topic, a PRV is in no way shape or form a check valve.


TM I miss ya my man. How ya doin'? :laughing:


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## SewerRatz (Apr 25, 2009)

Tommy plumber said:


> True Matt, in backflow class we were taught that RPZ's and DC's are required to be able to be tested and re-certified 'in-line'. Repaired also as you state. That is also why devices cannot be sold w/o (2) ball valves. Must be ball valves, not gates anymore.


I never seen a brand new 6" Watts 909 with ball valves.


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## Pipe Rat (Apr 5, 2009)

Plumber666:laughing: 1 post :laughing: Hey Brother I am rootin for ya :thumbsup:


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## ILPlumber (Jun 17, 2008)

Piperat said:


> TM I miss ya my man. How ya doin'? :laughing:


Nope.

I'll let him intro himself though.


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## Don The Plumber (Feb 14, 2010)

I know that a PRV is not a backflow preventer, by code, but will it physically stop backflow, say from thermal expansion?


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## Redwood (Sep 8, 2008)

Don The Plumber said:


> I know that a PRV is not a backflow preventer, by code, but will it physically stop backflow, say from thermal expansion?


Yes, unless the PRV has an integral bypass and pressure on the supply side is low enough to allow the pressure buildup from thermal expansion to return to the supply side through the bypass.


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## DUNBAR PLUMBING (Sep 11, 2008)

A Watts N55BU2 only opens up at 135psi, and that's only if the pressure doesn't match or is higher than the pressure pushing back.


I tell customers you cannot rely on the thermal expansion bypass when the pressure is that high. Something bad will come of that.


That's where the thermal expansion tank is golden; it can absorb as little as 1/2 pound of thermal expansion without loss of water through the system, or jacking pressure up beyond a preset setting of the prv.


That's what the whole purpose of the PRV is supposed to provide; not to exceed past it's predetermined setting. 

I replace thermal expansion tanks weekly. Money in the bank.


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