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One Pipe Gavity Pump Selection

NYplumber Member Posts: 503
One Pipe Gavity Pump Selection

Hi there wallies!

Last year thanksgiving we installed a steamer with a drop header & all the fun stuff. This past thanksgiving we installed a replacement boiler in a converted one pipe gravity system. The boiler that was being replaced got water damaged from the hurricane. Sand was all over the fire side, not to mention the salt water had already started doing its job on the metal surfaces. The boiler that was there was around 40 years old. Pretty clean for a boiler that didn't have any cold water protection.

The boiler we installed has a bypass loop to protect against return water under 140*f. Seems to be running fine except for one quirk. The basement isn't heating up!

From the reading I have done, these systems are picky with flow and need to be moved real slow, like lazy water gravitating up and down in the large mains. The current pump there is a 007. With the low head loss I figure it should be moving water pretty much at the high flow of its curve.

So, do I need more pump, or less pump?

The boiler is a 140k input. Radiator style is convectors pictured below. House has very old windows, and down the block from the beach (hence the sand in the boiler), so a boiler of this size wasn't much of an overkill. There is only a basement and first floor.

The gravity mains have interesting t's that I photographed for the enthusiast viewing pleasure. Return t's seem to be standard black t's.

Another interesting note, I have never had to bleed a radiator on a system I piped, however this one had much air days later in the upstairs radiators, even though piped away from ponpc. With all that air, the house heated up from the ambient cold to a toasty 70 in just a few hours after the install was completed, but the radiators were only luke warm, most likely due to air. The homeowner noted, that radiators that were never hot were now hot, while radiators that were previously hot, now only got like warm.

So, with that said, should I bump up to a 0010, get a steeper head pump, go with a vdt, or just keep it as is and figure out why the basement can't get flow. (Basement radiators look to be on the same main as the upstairs.)

Thanks in advance!


  • NYplumber
    NYplumber Member Posts: 503
    edited December 2012

    When it is thanksgiving afternoon, you get creative with the expansion tanks when a larger one isn't immediately available.

  • kcopp
    kcopp Member Posts: 4,431
    the picts...

    don't help much.... but I am going to say that does not look like a gravity system. Gravity systems would have no diverter tees. Also typically they would have large cast iron rads, no head loss... not convectors.

     Do you have just 1 circulator doing all the pumping? Boiler loop and out to the mains?
  • icesailor
    icesailor Member Posts: 7,265
    Chrome It:

    Growing up in Hollywood in the time if "American Graffiti", and actually having been around some of the stunts in the movie (They claimed it happened in Van Nuys but it happened in Glendale), there was a saying: "If it don't go, chrome it". The same now happens in hydronic heating. If it worked for years before, and you do something to the system, "Pump It Up". Put a bigger pump on it Try one of those really big high volume, high head pumps. Prove all those old dead wet heads wrong, that a bigger pump would have made those Mono-flow and gravity systems work better. And the best part of over pumping a Mono-Flow system is that the high volume, high speed water travel will make LOTS of turbulence. Especially if you crank the high limit setting to 200 degrees to make it heat faster. Then, the negative pressures in the higher parts of the system will make steam and fill the upper heat emitters with air. Even though, the longer and slower the pumps seem to run, the better the system seemed to work for the old dead guys.

    From an old guy who will one day join the ranks of old dead wet heads, raise the system pressure to 18# to 20#, drop the high limit to 180 degrees or below,  and let it run for a while. It will work. It ALWAYS worked. If it has a tankless and needs the higher water temperatures to give suitable DHW, install a storage tank. The old boiler probably contained a lot more water and stored more energy that the new "Flash In The Pan Boiler".

    Or continue on your path. It might work for you. It never worked for me, and I've never seen it work for anyone else. But it might work for you.
  • NYplumber
    NYplumber Member Posts: 503
    one pump

    Pumping through the boiler and out to the rads like the old system.
  • NYplumber
    NYplumber Member Posts: 503

    I'm not sure if your being cynical or just have a tad of humor. Not saying I need more flow, but more head pressure may force water through the large interesting flow T's and down into the rads due to the larger pressure differential, because low head and moderate flow isn't doing the trick.
  • icesailor
    icesailor Member Posts: 7,265
    "Head" aches:

    Where is all this air coming from? That's what I want to know. I have old systems that run for years and have never had a radiator bleed key inserted. Because the painters always paints the valves shut.

    If you open an air vent on the top floor and you don't get a rush of steady air, you don't have enough pressure in the system.

    It has always been my understanding that the function of a circulator pump isn't to raise the head pressure in a heat system, but to create enough pressure to overcome the piping resistance in the system.

    If you look at that Tridicator Gauge thingy on the boiler, it reads temperature AND Pressure in PSI and head/feet of water above the gauge. My old dead wethead boss used to tell me to never trust a gauge.

    But, if you look at the pressure in PSI Gauge and read the corresponding scale on the other side that says something about "altitude" or "Head in Feet", take a tape and measure from the center of the gauge and UP until you get to the radiator air vent on the highest radiator. Or, take the PSI Gauge and multiply it times (X) 2.31. That tells you how high water would be in a column of water, 100' +/- in the column. If your level isn't considerably above that vent, you will get air. If you have auto air vents, they will suck air. AND REMEMBER THIS!!!!! If the Extrol tank is too small, it will be doing it all the time. If you have a #30, add a #60 in tandem with it.

    A  bigger pump isn't the solution. Especially if it was working for many years before you were born. Just because someone came up with their better idea for a bigger pump, doesn't mean it is needed.
  • icesailor
    icesailor Member Posts: 7,265

    The Venturi or Flow Tees were usually connected to a main that was larger than the risers. To keep the flow as unrestricted as possible. But unlike the "Jet" well pump, where the pump, pumps 4 gallons into the nozzle, and 5 gallons come out of the venturi, this doesn't happen in mono-flow or venturi tees. A small amount of water gets "diverted" through the "nozzle" and comes back into the flow on the other side, depending on how the tees are placed. The same amount of water that enters the first tee, will be going out the second tee. REGARDLESS. It is physically impossible to do it any other way.

    If you opened the flow check, and let the system run for a day on "gravity", the whole system would get hot.

    You don't get the point of the ferris wheel. It is in balance. Whether it is laying on its side, or standing vertical, it takes about the same amount of HP to spin it either way. In a closed system, you need to stop thinking about getting water up to the third floor shower head. The hydronic heat system is always in balance. Just like the steam system. Hot steam is light and rises. Condensed steam is cooler, heavier and falls. Its the in between that we utilize
  • Steamhead
    Steamhead Member Posts: 16,823
    edited November 2012
    I don't think this was ever a gravity system

    one-pipe gravity would never have had basement radiators. It was barely possible to make basement radiation work on 2-pipe gravity systems.

    Those tees look like Taco Venturi fittings. They were used in a system called "Taco-One" which was Taco's answer to the B&G "Monoflo" system. Think "diverter-tee", not one-pipe gravity.

    You need more pump here. You're not developing enough ΔP to make the tees do their job. Start with at least a Taco 0010.

    What circ was there before? Are you certain the water is flowing in the proper direction?
    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
  • NYplumber
    NYplumber Member Posts: 503

    Thanks Frank for the post!

    The system is flowing in the correct direction. I wasn't sure if it was a gravity or monoflow style, but regardless I had a feeling there had to be a greater delta-p on the system to make it work. Thinking it was a gravity, I was hesitant to start with a 0010 due to fear of over pumping.

    As for the other posts here, there are no auto vents in the system, and no 'new' air being introduced. I was just curiouse as to why the air wasn't being eliminated on its own after the innitial fill as is usually the case. An undersized pump as Steamhead pointed out. Right size pump, the air will be entertained in the water.

    I will replace with a 15-58 and start on speed one to see how things heat, then bump up to higher speeds if needed. Speed one may be sufficient due to the high head characteristics of the pump.
  • Gordan
    Gordan Member Posts: 891
    You can't power-purge a diverter tee system

    Those bleeders are there with good reason. Dan H has a great "how come?" writeup on the quirks of series-parallel circuits which I highly recommend you take a couple of minutes to read. It's informative as well as entertaining, just as we've come to expect of our host!
  • NYplumber
    NYplumber Member Posts: 503
    which book

    Is it in the how come book? I have most of Dans books as they are the cat in the hat books in comparison to the techy books in the office library, and always enjoyable to read.

    As for not being able to power purge, I have power purged many b&g monoflow systems, then turned them on and let the pump do the rest of the work.

    I have the 0010 on the truck and will report shortly how it works.
  • Gordan
    Gordan Member Posts: 891

    I'm glad it has worked for you; it's never worked for me. Water has a shorter path along the main than up and down the risers and the pressure nearly equalizes across the tees. Since the risers are empty there's gravity adding to the pressure differential along the branch, and the water simply doesn't want to go there. It's like trying to purge a radiant system with all the loops open, only worse.

    What HAS worked is simply filling from bottom to top and bleeding each emitter from bottom to top, and from supply to return. After a while, you repeat it to just get rid of any remaining bubbles, although typically not much air will come out.

    Dan's article is actually right on this site... it's what originally got me here when I was trying to figure out diverter tees many years ago!

  • NYplumber
    NYplumber Member Posts: 503

    Moving more water at more head cured the lack of heating woes.

    Thanks for the help.
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