Laing Hot Water Recirculation Method-minimizing air in line

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by gplumb, Feb 5, 2007.

  1. gplumb

    gplumb New Member

    Messages:
    32
    Location:
    North Carolina
    I have looked into using the Laing method of connection, but they are the only pump manufacturer that specifies the use of the air vent near the pump (before pump if connecting to drain and after pump if connected to cold inlet). They also want the pump mounted below the top of the tank. They seem more concerned about air in the line damaging the pump then the the other pump manufacturers. Does anyone follow the advice about mounting their pump or other manufacturer's pumps below the tank top. Does anyone install the air vent (Watts FV-4M1)? To install it an air scoop has to be built out of 1 1/4" pipe and a threaded fitting put on it. My plumber said it would cost around $50 just to build the air scoop. Is there an auto air vent that already has the scoop?:)
  2. Gary Swart

    Gary Swart In the Trades

    Messages:
    7,358
    Location:
    Yakima WA
    I have a Laing 303 and have it installed exactly as specified. Yes, they do seem very concerned about keeping air out of the pump. I figure they make the unit, and they should know how it should be installed. I don't know where you get the idea you need some kind of "air scoop" and what purpose it would serve. The auto vent valve just bleeds small amount of air out of the line as needed. The hose bib is for major system bleeding after the lines have been drained for some reason. You are not drawing air into the system, and the tiny amounts that bleed automatically are not even noticed. Just go by the installation diagram.
  3. gplumb

    gplumb New Member

    Messages:
    32
    Location:
    North Carolina
    Re: Auto Air vent

    In the spec sheet installation instructions (http://www.watts.com/pro/_productsFull.asp?pid=664&ref=1) for the Watts FV-4M1 auto air vent the air scoop is "for the venting of air while the fluid is circulating in the system." Without the air scoop "the air will not be vented while the fluid is circulating in the system, but it can vent when the system is shut off." So it depends if you have the vent mounted at a high point in the system so air reaches the vent when the system is not circulating. From the Laing installation diagram, when the recirc line feeds back to the cold inlet, they mount the vent above the water heater after the pump. Why the difference? When the recirc line goes back to the water heater drain, the vent is mounted before the pump, and it is at a low point in the entire system. It seems that at least in the latter case the air would not rise to the air vent during periods of non-circulation so you would want to install an air scoop to vent during circulation. Maybe to be safe the air scoop should be used with either installation method. Maybe Laing will have to answer the question about whether they intend the use of the air scoop. :)
  4. Gary Swart

    Gary Swart In the Trades

    Messages:
    7,358
    Location:
    Yakima WA
    You should contact Laing Customer Service and get their take on this air scoop. I had never heard of this until now, and I'm not really sure it's needed. At least I have never used one, and the Laing site and installation guide makes no mention of it. I've had no problems with my system for 3 or 4 years. Kindly report back if you contact Laing and get an answer from them.
  5. got_nailed

    got_nailed DIY Senior Member

    Messages:
    277
    I was searching there site and I don’t see any air scoop’s on there site. I just want to see what it looks like…
  6. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,134
    Location:
    New England
    Laing may or may not actually make an air scoop. There are various manufacturers that make air extraction devices. One is Spirovent.
  7. gplumb

    gplumb New Member

    Messages:
    32
    Location:
    North Carolina
    Lainng doesn't make one but recommends the Watts FV-4M1. Unfortunately they don't offer a simple air scoop for 1/2" or 3/4" copper pipe for ptoable water. They do make a cast iron air scoop in 1" - 3" sizes for hydronic heating systems. The Spirovent from Spirotherm is for hydronic heating systems, is very expensive and may not be suitable for potable water. I still haven't found anything equivalent to the Watts, but they only make an air scoop so you have to build one from pipe. :)
  8. Rancher

    Rancher Guest

    What about the Watts AS-B air separator..


    Series AS-B
    Air Separators
    Sizes: 3⁄4", 1" and 11⁄4" (20, 25 and 32mm)
    Series AS-B is all bronze and perfect for radiant heating applications. It's unique separates and collects even the smallest micro-bubbles for fast efficient and continuous removal from all hydronic systems. Series AS-B has tappings for the installation of expansion tank, air vent and for boiler fill piping. It also includes 1⁄2" FV-4M1 air vent.


    And it says it comes with the vent...

    Rancher
  9. gplumb

    gplumb New Member

    Messages:
    32
    Location:
    North Carolina
    Thanks but as I said in my post "Unfortunately they don't offer a simple air scoop for 1/2" or 3/4" copper pipe for potable water." They give instructions in the FV-4M1 air vent installation sheet on how to construct such an air scoop from copper pipe. The Series AS-B is for hydronic heating systems and is not rated for potable (drinkable) water. It also has a 3rd pipe connection for the heat system and a 4th for an expansion tank. For the typical recirculation system with a 1/2" return line, a 1/2" air scoop would be needed. Laing recommends the use of the 1/4" FV-4M1 when using a 1/2" return line.:)
  10. dubldare

    dubldare Plumber/Gasfitter

    Messages:
    286
    Location:
    MN/ND
    Get the biggest one you can and use bushings, black iron ones. :D
  11. gplumb

    gplumb New Member

    Messages:
    32
    Location:
    North Carolina
    ??????? I think you replied to the wrong thread.:)
  12. Rancher

    Rancher Guest

    Sorry I don't see anywhere that it's not rated for potable water, it does say it's "designed for efficient separation of air from water in hydronic heating sytems". It's made out of Bronze, that's about as safe for potable water as you can get... They also say the FV-4M1 air vent is for Hydronic Heating Applications, so perhaps you shouldn't use it with a homebuilt air scoop...

    Rancher
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