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Thread: Water heater and "closed" systems

  1. #1
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    Default Water heater and "closed" systems

    What's the difference between an open and closed system? How do you find the pressure on a hot water heater? Does it have a pressure gauge that I'm missing? How difficult is an expansion tank to install?

  2. #2
    Master Plumber master plumber mark's Avatar
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    Talking expansion tank

    a closed system is one with a check valve in the line that
    restricts the water from backflowing into the cold side of the system...

    A check valve at the water meter or a PRV valve makes your home a closed system.

    Installing a thermal expansion take allows the pressure to expand into the tank....

    they are fairly simple to install on the cold inlet to the
    water heater....as long as it has some support to hold the weight

    pics are available ....

    .

  3. #3
    In the Trades Gary Swart's Avatar
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    Good, straight forward questions!. A closed system is created when there is a check valve between the water heater and the city water main. This is usually in the form of a bell-shaped pressure regulator which is normal located very close to the water pipe's entry to the house. Some new water meters also have a check valve. When water heats, it expands. Since water does not compress, this expansion has to either be absorbed somewhere or the pressure within the closed system will rise to the point that the T/P valve on the top or side of the water heater will trip. While the leaking water is a PITA, this prevents the heater from exploding which could ruin your whole week! A thermal expansion tank is a canister with a rubber bladder that is charged with air pressure to approximately the same as the incoming water pressure as regulated by the pressure regulator valve. It is located in the cold water line somewhere between the PRV and the water heater and acts as temporary for the expanded water. The pressure gauge you refer to is an inexpensive gauge that you can purchase at any hardware or plumbing store. They can be attached to any fixture with a hose thread. You must have one to set a PRV and balance the pressure in the expansion tank. Expansion tank installation is not difficult, but like anything, it does require some basic skill. As noted, the location is in the cold water intake line. You cut it open, install a tee to which you would have already install the adapter to attach the tank to. The tank can be mounted in any position desired, but it has some weight, especially if/when the bladder fails and the tank fills with water, so it must be supported well. The carton it comes in has illustrations of possible ways this can be done. So, about the only skill you need is to be able to sweat copper. Air pressure is adjusted with an air pump through a Schrader valve, just like a tire. They recommend using a bicycle pump rather than a big compressor as the actual volume of air is quite small, but with care and common sense, a regular compressor will work.

  4. #4
    Plumbing Designer FloridaOrange's Avatar
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    Quote Originally Posted by Gary Swart View Post
    Good, straight forward questions!.
    Where's the fun in that?
    Matt
    Semi-professional plumbing designer
    Enjoying life in SW Florida

  5. #5
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    Thanks for the help. I'm a pool technician so I have the basic skills to plumb and I understand the dynamics of plumbing as well. My problem is I had a new hot water heater installed and ever since the install I have HOT water leaking from my bathroom faucet and my shower head. I can also feel a hot pipe in the floor all of a sudden. I'm hoping with some advice as to what's causing this problem and a little luck I can fix this problem myself. I was told the pressure might be to high so it's forcing water out at the weak points. How would I check the pressure exactly? I also thought it could need an expansion tank or it might be a faulty valve or two somewhere? I'm looking for some help as to where to start. Thx>

  6. #6
    Plumbing Contractor C NUMB's Avatar
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    I would start by fixing the faucets in the bathroom, may have some debris in the hot side. Additional pressure on the hot side should not be coming out of any faucets, it would pop the relief valve open first. The line feeling warmer in the floor may be due to water running thru non stop to those leaking faucets. I also would install an expansion tank at the heater just to be safe.
    I'd Rather Be FISHIN'

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