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Dead Men Tales: Special Tees

HeatingHelp Administrator Posts: 634
edited February 2022 in THE MAIN WALL

Special Tees

In this episode, Dan Holohan tells us about the inventive tees used in early hot-water heating systems.

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  • retiredguy
    retiredguy Member Posts: 883
    Great educational story about the development of what became known as the "mono-flo tee.

    Thanks Dan
  • Larry Weingarten
    Larry Weingarten Member Posts: 3,233
    Now I'm thinking about biting into a crisp apple and paying close attention to the sound of it! :p

    Yours, Larry
  • DanHolohan
    DanHolohan Member, Moderator, Administrator Posts: 16,490
    Thanks, guys!
    Retired and loving it.
  • ccstelmo
    ccstelmo Member Posts: 29
    Try this one - and you can slap me upside the head if you want but it worked for me. This is not about heating but plumbing.

    When I was comin' up (resort towns in the Rockies) I eventually noticed that we were replacing a lot of leaky, pin-holey, copper pipe in hot water recirculating systems. After reading some of Dans' stuff I got it in my head that those pin-holes were caused by entrained air tumbling along inside the pipe. I suppose now that oversized recirc pumps had a lot to do with it too, but my thought then was that fresh water, heated in the water heater, was releasing micro-bubbles into the stream, that they conspired and all got together and traveled in a pack and were abrasive to the interior of the pipe (especially down-stream from elbows). (BTW, about that time, and because of this, I got seduced by pipe bending (as in Holsclaw) over the use of elbows).

    OK, Fast forward. I got retired and had enough scratch to build my own dream house in the mountains. Off the top of my 80-gallon heat exchange tank was a big fat 1-1/2" tap. It's a big house, a bed & breakfast, actually, and there's multiple recirc lines going hither, thither, and yon. I didn't want 'em deteriorating - ever - so the wheels started turning in my head.

    Ever heard of a twin-ell? I expect so. I got a brass one. Rare bird at the time. Rarer still now. It's a (dare I say it?) DWV fitting. Kinda like a hybrid tee, right? I modified the twin ell by silver-soldering a baffle into the branch. (I sense a lot of you guys are rolling your eyes about now. Give me a chance - stay with me.

    So I came off the top of the tank, set a union, short piece of pipe, and a 1-1/2"X1"X1-1/2" tee. The 1" run continues vertically to a 1" valve with a 1" tee set vertically above that. The 1-1/2" branch is directed into the horizontally baffled branch of the vertically set twin ell. One run of the twin ell continues vertically through a 1-1/2"X1/2" reducer to an automatic air vent above. The other run, the downward one, goes into the trap part of a DWV p-trap (GASP) and comes out vertically to an 1-1/2"X1" reducer with a 1" valve above it then makes its way vertically into the branch of the 1" tee aforesaid. (BTW: selected joints are silver soldered because of shallower DWV sockets.)

    So here's what happens. The 1" valve directly above the 1-1/2"X1"X1-1/2" tee is closed. The water in the tank is in motion because of the recirc pump. The air drops out of the cold supply water when it's heated and, entrained, heads for the 1-1/2" tank outlet above. Then it enters the tee, and is directed out the branch toward the twin-ell branch. Because it's air, it wants to gather at the top of the 1-1/2" pipe (a wide place in the road) and does. And just about then it enters the horizontally baffled twin-ell branch, is captured within the twin-ell and, divorced from the water by the baffle, gets directed upward to the air vent. The water, captured lower in the twin-ell by the baffle, is directed downward, exits the trap vertically, and heads toward the branch of the 1" tee above and the house beyond.

    Every once in a while when I'm down in that mechanical room I hear that air vent open and spit out air. It's been doing it now for 14 years. I smile. No pin-holes for me.

    Larry Weingarten
  • DanHolohan
    DanHolohan Member, Moderator, Administrator Posts: 16,490
    @ccstelmo, that is a GREAT story! Thanks for sharing it with us.
    Retired and loving it.