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Thread: Supply lines ran overhead..air lock concern?

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    Water system engineer riverside67's Avatar
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    Default Supply lines ran overhead..air lock concern?

    I am building a new home and my plumber wants to run many of the supply lines to the bathrooms ,and outside spigots, overhead instead of under the slab. I am concerned about air becoming trapped inside the lines ultimately reducing the volume of the supply lines.

    I have voiced my concerns to him and he does not seem to convinced there would be any problem. I am very familiar with air in lines as I am a water system engineer. I was asking him what about installing a spigot in each line at the high points overhead...This way we could manually release any air pockets, as needed, in the attic via the hose spigots. This would only be upon first charging of the line and upon any repair of the lines that would've drained them. Of course, trapped air in the lines could also contribute, but to a much lesser extent.

    Anyone have any familiarity with such a situation of a solution?

    Thanks!

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    Forum Admin, Expert Plumber Terry's Avatar
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    You are thinking of a closed system like a boiler would have. A closed system has air bleeds.
    You have an open system. As soon as you open the hosebib, it will flush the entire line out.

    Closed,
    For boilers, hot water heating systems and warm water radiators, they need an air bleed

    Open,
    For faucets, they have an air bleed, the faucet itself.

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    Water system engineer riverside67's Avatar
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    The supply lines will run over the ceiling and then will come down the walls to the sinks, showers, tubs, etc. Do you think all the air will be forced out through these fixtures? I believe some air will be trapped in the line above the ceiling, even if it is just air from the water. Over time this can accumulate is the segment above the ceiling can't it?

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    Forum Admin, Expert Plumber Terry's Avatar
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    No.
    Many re pipes are done that way and many new homes and condos.
    A first floor condo usually have the pipes run overhead and then dropped down.
    That's why the journeyman runs the waste and vents and leaves the water supply to the apprentice.
    You can't screw up water.

    Even "air chambers" will become waterlogged.
    Last edited by Terry; 05-23-2010 at 07:28 PM.

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    Journeyman & Gas Fitter Doherty Plumbing's Avatar
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    Like Terry said you won't have a problem. The force of the rushing water through the pipes will PUSH out all of the air.

    You have nothing to worry about.

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    Forum Admin, Expert Plumber Terry's Avatar
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    A radiator system is on a "closed" loop.
    The only outlet is an air bleed.

    Home plumbing is not a loop, it filled with outlets. Everytime a faucet is turned on, water rushes out of the ends.
    You home is a giant "water fall" producing machine. If you turn on all the faucets at once, you can call your insurance agent to come over and see the lake you create.

    A closed loop won't do that.

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    Water system engineer riverside67's Avatar
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    Hmmm...

    Water distribution systems are designed with air relief in mind at all high points in the system. Sometimes a customer's service/meter IS the high point...i.e. when the customer uses water through his system any air at the end of the main will be drawn out of the main. This does not mean that the customer's system will remove all of the air from his own system.

    Ok so here's a real world example. I was installing my irrigation system, composed of a 1.5" pvc trunk line. This trunk line ran across 300' alongside my driveway. Midpoint was a highpoint in the driveway..i.e. beginning and end of trunk line was lower than mid point by about 1'. When I went to flush the line (obviously full of air) I found that the volume at the end of the line was not what it should have been considering the line size and pressure...I thought oh crap, there is a high point where the air is being compressed and it can't get out...that air needs to be able to be blown off somehow...I capped the end of the line to fully pressurize to check for leaks and then cut into the line at the mid (high) point and OMG the amount of air that blew out at me was unbelievable and was under very high pressure. My suspicion was correct. I installed a tee and riser with a valve for future blow offs when needed (repairs, breaks, etc)...

    You see, air can compress but water cannot and after time a bubble of air can get so big that it reduces the ID of the pipe in a specific area, thus limiting overall volume.

    This is one reason why water distribution systems are designed with air valves at strategic locations. We cannot allow a water systems volume to be reduced, especially under fire flow conditions.

    Basically when lines are ran overhead it is like taking a sink trap and turning it upside down and putting it under pressure and expecting all the air to come out...I believe it won't happen.

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    Master Plumber Redwood's Avatar
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    I concur with the statements of the plumbers...

    Engineers I have found tend to focus sometimes on insignificant details...
    This is one of those times...

    In engineering many things are often much more difficult than they seem...
    This is not one of those times...
    Last edited by Redwood; 05-24-2010 at 06:41 AM.

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    Plumber jimbo's Avatar
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    I live in a two story condo. All the water supplies enter the building at a manifold, waist high above grade. The pipes for the first floor units run through their ceiling, and drop down to the sinks,, showers, etc. The supplies for the 2nd floor run all the way to the attic, across the ceilings and down to the sinks, etc.

    Could there be smoke from lefty Luckies mixed with the air in someone's pipes?

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    Water system engineer riverside67's Avatar
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    Redwood, I agree that engineers have a tendency to "over engineer" things sometimes...This may be one of those times and is why I'm here asking plumbers this question. I realize a home is not a public water system and therefore needed to get realistic feedback from plumbers who have encountered such installations. I don't want to overly complicate things for my plumber.

  11. #11

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    It makes sense to me that the floors get busted up and the pipes run in the ground.
    Have you ever worked on a ladder? Pretty scary. So take my advice and break out the concrete and put them below ground. You will be glad you did.

    Have you evers seen a geyser in Yellowstone? They all spray up, not down. 'So I say make the water spray up and not down. Make sense?
    Joe the Plumber

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    Water system engineer riverside67's Avatar
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    This is new construction. No concrete to break, just to pour.

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    Moderator & Master Plumber hj's Avatar
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    The ONLY thing that can restrict the flow of water through an "open" pipe is a physical obstruction, NOT a water pocket. IF your initial pressure AND volume are adequate it will "push" any air out of the pipe. IF the source of the water is inadequate, it will NOT push the air out, BUT the pipe will still deliver ALL the water you have available feeding the pipe. In other words, IF you have a 1/2" pipe feeding into a 2" pipe, it will NOT have either the volume or velocity to purge the air from a high point, but NEITHER will the high point reduce the amount of air flowing IN TO, and OUT OF the larger pipe.

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    Forum Admin, Expert Plumber Terry's Avatar
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    You may want to read the other threads on copper lines developing holes under concrete.
    Copper and concrete are not a real good mix.

    http://www.terrylove.com/forums/show...ab-leak-repair

    Last edited by Terry; 05-24-2010 at 10:29 AM.

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    Journeyman & Gas Fitter Doherty Plumbing's Avatar
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    I NEVER like burying copper lines in concrete if I can avoid it simply because if you do have a problem with one of the lines then it becomes a big problem. Instead of busting open your ceiling and fixing a leak you're tearing out your floor and jack hammering up the concrete hoping you can find where the leak is coming from.... not a good scenerio.

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