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Calling all plumbers- PRV on main and Expansion

GWGW Posts: 3,428Member
Got a 6 unit apartment with abound 100 psi- need to drop the pressure some. My question- why do some PRVs tend to make the P&T valves blow off some pressure (without an expansion tank) and other PRV installs don't?

This building has 6 basic gas water heaters, 30 gal. It would be a bit of a pain to install 6 small exp tanks, so perhaps i would throw the dart at the wall and guess at a good sized 'medium' tank



Gary Wilson
Wilson Services, Inc
Northampton, MA
www.wilsonph.com
[email protected]

Comments

  • pecmsgpecmsg Posts: 837Member
    PRV's are also a check valve. The expansion cant go beck into the city lines as such an expansion tank is required!
  • Jamie HallJamie Hall Posts: 10,672Member
    As a general rule -- can't comment on specific models -- PRVs also prevent backflow. Therefore... if you have a water heater on the downstream side, you will have a pressure rise when the heater operates. How much? Depends on the system involved. That said, an expansion tank is -- in my humble opinion -- mandatory. I'd throw a dart at the wall myself -- but technically you could size it in the same way you'd size one for a hot water heating system.
    Jamie



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



    Hoffman Equipped System (all original except boiler), Weil-Mclain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
  • Larry WeingartenLarry Weingarten Posts: 1,530Member
    Hello, I d look at the tenants first. Do they get up and go to work all around the same time? If so you need to size a tank based on the total volume of all heaters. If you have retired folks, the expansion tank could likely be smaller. Is there anything preventing back flow other than the reducer? That would mess with using just one tank. My experience with PRVs is the little ball check valve gets stuck closed, preventing backflow from expansion. Hope that helps.

    Yours, Larry
  • Intplm.Intplm. Posts: 781Member
    @GW . No need to over think this. Go to the Watts Webb sight. There they describe the two types of PRV's

    Surely you should have an expansion tank. It is needed due to fluctuation in the main when the PRV or even a BFP is installed on some water mains. As you know size does matter.Commonly fixture unit calculations come into play for sizing fixtures/demand issues of the system. Not so much the age or type of occupants.

    You should be able to get the size you need if you like, by rule of thumb. To start go with the water main size first. Then see the webb sight if applicable.It's what I have done for years and has worked out fine.
  • mak62mak62 Posts: 11Member
    Here is Amtrol chart for sizing tanks
  • EBEBRATT-EdEBEBRATT-Ed Posts: 5,921Member
    edited February 16
    Some jobs with prvs don't blow the relief there is enough constant water usage so pressure never builds
  • Many PRV's have a by-pass to sneak thermal expansion back into the main, but I've never seen them work as advertised.

    See one here.
    Often wrong, never in doubt.

    Click here to learn more about this contractor.
  • GWGW Posts: 3,428Member
    Thanks all I have seen many prv installs over the years w/o an expansion tank.

    I did look at my Amtrol app and the result was this crazy expensive commercial expansion tank. It seemed to base its calculation on total gallons of HW and total BTU of the water heaters

    The tenants have all sorts of differing schedules

    I’ll look at the other manufacturers of expansion tanks to see other charts

    Thanks
    Gary Wilson
    Wilson Services, Inc
    Northampton, MA
    www.wilsonph.com
    [email protected]
  • hot_rodhot_rod Posts: 11,684Member
    Really not much value in the bypass PRVs anymore as most public water systems want some degree of BFD on every connection. The city or water department supplies potable water to the building, once it goes into a building it is no longer considered potable to them and they really don't want if flowing back into their mains under any condition, not knowing what is may have contacted inside a home or building, lawn sprinkler, fire protection, etc.

    I think it is wise to have a thermal expansion vessel on all systems as they either do or will have BFDs.

    There are other pressure protection options, Watts used to make a "governor" a toilet ballcock with a mini PRV, but they had a habit of wasting a lot of water down the overflow tube every time they pop, off when they fail. Homeowners were unaware of the amount they could dump until they got the water bill :)
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
  • GWGW Posts: 3,428Member
    Watts toilet fill valve, wow. I’ve been out of the loop for a while, never heard of that
    Gary Wilson
    Wilson Services, Inc
    Northampton, MA
    www.wilsonph.com
    [email protected]
  • hot_rodhot_rod Posts: 11,684Member
    GW said:

    Watts toilet fill valve, wow. I’ve been out of the loop for a while, never heard of that

    Looks like they have been discontinued, too much water waste potential, I suppose.

    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
  • GWGW Posts: 3,428Member
    edited February 23
    Our big plumbing job this week- when the water dept finally got the water off i said, 'give me 6 minutes to change the valve, well, make it 7". I didn't time myself but I spun the old and new really quick-like











    Gary Wilson
    Wilson Services, Inc
    Northampton, MA
    www.wilsonph.com
    [email protected]
  • I like that - a valve on each side of the union. You can tell when someone does a lot of service work - they pipe it smart for the next guy.
    Often wrong, never in doubt.

    Click here to learn more about this contractor.
  • pecmsgpecmsg Posts: 837Member
    Next thing is get Sparkey in there too fix the grounding issues!
  • GWGW Posts: 3,428Member
    Yes Alan I wear all hats
    Gary Wilson
    Wilson Services, Inc
    Northampton, MA
    www.wilsonph.com
    [email protected]
  • GWGW Posts: 3,428Member
    Hey pecmsg I’m not super inclined in the finer points, what could be better? Other than it’s ugly? (This is my rental property, trying to pimp it out here and there)
    Gary Wilson
    Wilson Services, Inc
    Northampton, MA
    www.wilsonph.com
    [email protected]
  • Danny ScullyDanny Scully Posts: 1,193Member
    edited February 24
    @gw, what’s with the one foot in one foot out with pro-press. Dive it already! 😉 Let me guess, getting rid of old stock?
  • GWGW Posts: 3,428Member
    edited February 24
    I'm a switch hitter. I solder when I want/need smaller patterns and such. Plus I'm a cheapie---I will solder ball valves and male adapters for pukers here and there. And PP caps--I would rather stick my hand in the mouth of a big cat fish than press on caps- them things are expensive (wow i need to read to see what my sausage fingers are typing)
    Gary Wilson
    Wilson Services, Inc
    Northampton, MA
    www.wilsonph.com
    [email protected]
  • Danny ScullyDanny Scully Posts: 1,193Member
    edited February 24
    Don’t miss the forest for the trees @gw. The only thing you can realistically control is your labor time...then again you’re doing fine and have been for quite awhile so do whatever you want :lol:
  • GWGW Posts: 3,428Member
    edited February 24
    I guess-- we all get to chose the battles. For Example-Cutting tubing: I don't like the battery (Milwaukee) cutter---too slow. I can cut copper twice as fast with my #15. It's not just the 'cut time', it's the fact that i can put my cutter wheel exactly where i want- no need to 'mark the pipe". My guys love the Milwaukee. But they pull their Sharpie out of their pocket, mark the pipe, put their sharpie back, get the Milwaukee on there, watch the tool spin for 20 seconds, and it's done. I can do it in half the time.
    (edit- probably faster than half the time)
    Gary Wilson
    Wilson Services, Inc
    Northampton, MA
    www.wilsonph.com
    [email protected]
  • Danny ScullyDanny Scully Posts: 1,193Member
    You should still mark the pipe @gw :wink:
  • GWGW Posts: 3,428Member
    Danny, what's got a finer edge, a sharpie or a cutter wheel? C'mon it's a wheel right? I think I'm the only dude that can cut w/o marking. I've tried to teach my guys but it's like grabbing an eel, it just takes some getting used to.
    Gary Wilson
    Wilson Services, Inc
    Northampton, MA
    www.wilsonph.com
    [email protected]
  • pecmsgpecmsg Posts: 837Member
    GW said:

    Hey pecmsg I’m not super inclined in the finer points, what could be better? Other than it’s ugly? (This is my rental property, trying to pimp it out here and there)

    There should be a solid ground from the meter thru the panel to a ground rod and the cold water main.

    What is all those wires doing there?
  • GWGW Posts: 3,428Member
    There are 7 elec meters, does that make it better? It's a 6 unit, which is what prompted the initial discussion. i didn't know how to work with 6 water heaters possibly blowing off the pukers
    Gary Wilson
    Wilson Services, Inc
    Northampton, MA
    www.wilsonph.com
    [email protected]
  • I love my Milwaukee tubing cutter. What makes me faster than your #15 is my BIC retractable marker. No cap to remove and replace.



    Bring your #15 to the gathering in August and we'll put it to the test.
    Often wrong, never in doubt.

    Click here to learn more about this contractor.
  • hot_rodhot_rod Posts: 11,684Member
    I agree with measure the tube, put your thumb nail at the cut location, slide the Reed cutter up against the fingernail and spin away.

    A sharp cutter wheel makes quick work of copper cutting.

    Although for production work my old 10" miter saw with a 80 tooth, non ferrous blade chops burr free copper in a few seconds, always straight. Even faster than a portaband.

    Wear ear plugs and safety glasses..
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
  • "Although for production work my old 10" miter saw with a 80 tooth, non ferrous blade chops burr free copper in a few seconds, always straight. Even faster than a portaband."

    Did you mark the measurement with a Sharpie? Now, that'll slow you down.
    Often wrong, never in doubt.

    Click here to learn more about this contractor.
  • GWGW Posts: 3,428Member
    edited February 26
    Alan Yes! Do I sense a wager in the air? A fun little competition perhaps?

    HR I’ve seen the thumb nail method, it’s good, yet I can stick my wheel right on any point on the tape measure; 100% accuracy., one less motion of the hands too (I have the tape and the cutter in each hand as I approach the pipe)

    If I’m really hauling I will snap the tubing like a Sheetrocker snaps Sheetrock. But I can’t give out too many of my tricks just yet. New construction plumbers rule the roost with speedy piping (I’m a happily retired N/C plumber)
    Gary Wilson
    Wilson Services, Inc
    Northampton, MA
    www.wilsonph.com
    [email protected]
  • hot_rodhot_rod Posts: 11,684Member
    good method, I've nicked a few tape measure blades that way, you have steadier hands.

    "Although for production work my old 10" miter saw with a 80 tooth, non ferrous blade chops burr free copper in a few seconds, always straight. Even faster than a portaband."

    Did you mark the measurement with a Sharpie? Now, that'll slow you down.

    I memorize where on the lettering on the tube the cut needs to be. Like the T in type L. :)
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
  • CanuckerCanucker Posts: 543Member
    > @Alan (California Radiant) Forbes said:
    > I love my Milwaukee tubing cutter. What makes me faster than your #15 is my BIC retractable marker. No cap to remove and replace.
    >
    >
    >
    > Bring your #15 to the gathering in August and we'll put it to the test.

    I didn't realize there was going to be plumbing and heating based carnival games. I don't think I want to miss that
    You can have it good, fast or cheap. Pick two
  • SuperTechSuperTech Posts: 938Member
    Good thread here... I just wanted to add that I was very disappointed with the performance of the Milwaukee tubing cutter, I don't even use it anymore. I can definitely get the job done faster manually.
  • hot_rodhot_rod Posts: 11,684Member
    Canucker said:

    > @Alan (California Radiant) Forbes said:

    > I love my Milwaukee tubing cutter. What makes me faster than your #15 is my BIC retractable marker. No cap to remove and replace.

    >

    >

    >

    > Bring your #15 to the gathering in August and we'll put it to the test.



    I didn't realize there was going to be plumbing and heating based carnival games. I don't think I want to miss that

    Lead wiping and pouring a proper lead joint? Or is lead verboten?
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
  • GWGW Posts: 3,428Member
    HR I was cutting 10 footers today of 1/2 3/4 and 1” copper (we mostly haul 20s, but the 5 year old van needed a trip to the shop today), the thumb nail was the way. Too much bend in the tube to do my trick. But 10 feet down to 6” or so (to small of a piece I need to so it the slow way), I can bust a move

    And yes indeed, eyeballing the letters. I normally do that with PVC
    Gary Wilson
    Wilson Services, Inc
    Northampton, MA
    www.wilsonph.com
    [email protected]
  • GWGW Posts: 3,428Member
    Carnival? That’s not very flattering geesh
    Gary Wilson
    Wilson Services, Inc
    Northampton, MA
    www.wilsonph.com
    [email protected]
  • GWGW Posts: 3,428Member
    HR you’re old enough to know how to wipe a joint ? No way!
    Gary Wilson
    Wilson Services, Inc
    Northampton, MA
    www.wilsonph.com
    [email protected]
  • hot_rodhot_rod Posts: 11,684Member
    I don’t know if that is a positive or negative, knowing how to handle lead👀
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
  • Larry WeingartenLarry Weingarten Posts: 1,530Member
    edited February 27
    Hi, To @hot_rod 's comment about lead wiping, Here's what an apprentice of yore did for his test. All wiped joints! :o

    Yours, Larry

    ps, He may be hiding his burned hands!


  • hot_rodhot_rod Posts: 11,684Member

    Hi, To @hot_rod 's comment about lead wiping, Here's what an apprentice of yore did for his test. All wiped joints! :o

    Yours, Larry

    ps, He may be hiding his burned hands!


    A wind powered chocolate fountain?
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
  • GWGW Posts: 3,428Member
    “Handling lead”

    Ok pouring a simple XH or SV lead and oakumn joint is pretty cake, but you can wipe a joint?
    Gary Wilson
    Wilson Services, Inc
    Northampton, MA
    www.wilsonph.com
    [email protected]
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