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  1. Rickard

    Rickard New Member

    Joined:
    Feb 10, 2008
    Messages:
    66
    Loc:
    Western NJ
    How much flow restriction will I get using a 3/4" flow check valve on a 1 1/4" pipe. It would be on the main line coming off the wood boiler with a taco 007 pushing it. I see the price of 1 1/4" flow checks and at $40 plus I'm more than 1/2 way to a Taco 007 with the check built in. Could I run two 3/4"in parallel ( I have a bunch of 3/4" flow checks lying around)?

    Thanks

    Dean

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  2. jebatty

    jebatty Minister of Fire

    Joined:
    Jan 1, 2008
    Messages:
    4,511
    Loc:
    Northern MN
    You will get a lot, but the decision rests on how much flow you need. In general, a 3/4 restriction will limit the system to approx 3/4 flow, but pipe resistance, turbulence, and other factors will impact the actual result. In cross-section area, it would take 3 3/4" lines to equal 1 1-1/4 line.

    I use 1-1/4 to 1 through an hx on the boiler side, Taco 009; and 3/4 on the hx storage side, Taco 007, about 3' of head, and a 50 micron filter. With a new filter my Taco 007 flow is about 5-6 gpm through the 3/4 line.
  3. Eric Johnson

    Eric Johnson Mod Emeritus

    Joined:
    Nov 18, 2005
    Messages:
    5,732
    Loc:
    Central NYS
    Why don't you buy a 007 with an integral flow check? They cost about $40 on Ebay and you kill two birds with one stone. I wouldn't restrict a 1.25-inch line down to 3/4.
  4. Rickard

    Rickard New Member

    Joined:
    Feb 10, 2008
    Messages:
    66
    Loc:
    Western NJ
    Thanks Guys

    wishful thinking isn't working.

    Dean
  5. BrownianHeatingTech

    BrownianHeatingTech Minister of Fire

    Joined:
    Oct 5, 2007
    Messages:
    1,253
    Loc:
    Northwood, NH
    As Eric said, just get the IFC pump.

    As far as actual flow, you'd need to know your GPM, water temp, and the CV of the flow check, and then you could calculate the restriction. It would take more than 3 3/4" flow checks to equal a 1-1/4" flow check, in most cases.

    Actual "maximum flow" through piping is quite high. If you can buy a big enough pump, you can cram an awful lot of water even though 1/2" pipe. The point at which you cannot flow any more fluid through a given orifice is called choked flow, and it's an impressively-high number.

    But when you start upping the flow rate, you introduce velocity noise, component damage due to cavitation, and your pump size (and, therefore, cost) requirements shoot up dramatically in order to combat the friction.

    Joe
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