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Automatic Taco air vent

bob eck
bob eck Member Posts: 930
Anyone have trouble with Taco 418 / 419 automatic air vents? A couple of heating contractors was using them on condensing gas boilers and they are only lasting about 4 years. Water leaking right out the top of the air vent. Pressure in the boiler / system no higher than 18 PSI. Contractors checked the boiler expansion tank and they are fine. Boiler relief valves are not releasing any water.
Would a Spirovent spirotop air vent work better and last longer?


  • Ironman
    Ironman Member Posts: 7,385
    I use Spirovent, Caleffi, Supervent and now Webstone MBR's and I've yet to see a Spirovent leak.

    4-5 years makes me question the water quality.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • Alan (California Radiant) Forbes
    I've never used a Spirotop, but Spirovents have a pretty good track record.

    I don't mean to hijack this thread, but I went searching on this topic and came up with this video.


    At about 2:45 in, Ray says that the Spirovent element is manufactured from an old piece of baseboard. C'mon.

    8.33 lbs./gal. x 60 min./hr. x 20°ΔT = 10,000 BTU's/hour

    Two btu per sq ft for degree difference for a slab
  • hot_rod
    hot_rod Member Posts: 22,353
    I'd highly recommend adding a hydroscopic cap to any auto vent installed in critical locations like that. We actually sell vents with these caps to many boiler manufacturer, as an OEM component,

    I would also add a service check valve to remove or eliminate the vent if ever needed.

    The cap fits most brands of vents R59681.

    502243A is a 1/2 auto vent with a hydroscopic cap included,

    502343A gets you auto vent, service check, and hydroscopic cap.
    Page 52 of the Caleffi pricebook.

    We also have an adapter to add a drain tube to air vents, route it out of harms way. NA10204. It turns that metric thread into a 1/4 MPT
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Dave H_2
    Dave H_2 Member Posts: 557

    Is this the vent right on top of the boiler? If so, what is the water quality like? This connection in the system may not see alot of flow past this connection and therefore alot of the "stuff" in the water may collect at this high point and the vent and more importantly the valve mechanism inside the vent.
    Remove the cap and the valve mechanism and see if it's "slimed".

    Clean and replace.

    Dave H.
    Dave H
  • Solid_Fuel_Man
    Solid_Fuel_Man Member Posts: 2,646
    I find that with most of my early installs where I only flushed with cold water and let the system run. The auto-vent (you pick the brand) slimes up with oily sludge. The water in these systems is always clear and no other signs of poor water quality or makeup water to oxidize ferrous components.

    I now power flush to remove initial air, heat the entire system up to operating temp and circulate. Then dump it all by power flushing each zone and the boiler until the entire system is cold. Iv also used Sentinel system cleaner and others on that initial fill before the second flush.

    I believe the slime is from cutting oil and flux. Get that out (kind of like skimming steam guys) and your auto vents will live a happy and long life.

    The spiro vent "having a piece of baseboard" in it really discredits my trust in that video. Ive never had one failure of a spirovent, and I have two at my personal home. I did have one bubble at the seam during an air test. I opened it up and used red Locktite to reseal it. Only issue I've seen with them and I've got dozens out there. I've also had good luck with the little Watts 1/8" auto vents for replacement of systems which have cast scoops. As @hot_rod said, a service valve before an auto-vent sure speeds things up later!
    Serving Northern Maine HVAC & Controls. I burn wood, it smells good!
  • hot_rod
    hot_rod Member Posts: 22,353
    Also avoid the habit of pushing the air release stem until water spits out. we have all done that to assure the tank, boiler, etc is air free.

    However that allows the crappy fluid to get into that valve stem. Dirt, sawdust, teflon tape shards, etc float or get forced up into those high point vents.

    Caleffi vents are designed to hold a small air pocket up top, and shut off tightly.

    That air space keeps the junk in the war from getting into that sensitive needle valve.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream