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  • Expansion tank placement

    I am installing an expansion tank because the T&P valve on my water heater is opening on each heating cycle. I understand that the tank must be installed on the cold water inlet between the water heater and the backflow preventer on the watermeter. Can it be installed anywhere between those two points or should it be located on the pipe leading directly to the heater? The spot that I want to install the tank so that it is out of the way is before the branch that leads to the water heater/washer. All the diagrams that I see have it located immediatly before the heater. I didn't know if this was nessasary or just for ease of illustration. I appreciate any information or feedback...thanks

  • #2
    You need to install the expansion tank on the cold water line between the shut off valve to the water heater tank and the tank itself. It should be within five feet of the tank. If you need to put it up out of the way mount a 3/4 drop earred ell to a ceiling joist just over the water heater and run your line to that. Then attach your expansion tank to the drop earred ell.

    You DO NOT want to have a valve between the expansion tank and the water heater. Check your static water pressure and be sure to adjust the air in your tank accordingly. If you have a lot of pressure fluctuations set the air in your expansion tank to 2 psig below the top spikes.
    Work hard, Play hard, Sleep easy.

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    • #3
      That is the correct placement for the expansion tank, BUT - if your t & p valve is blowing off you have a problem that one of those will not solve. That is a safety device. Two things can cause that too much pressure or too much heat. Use a pressure guage to check the water pressure at the closest hose bibb or laundry tub near the water heater. If you do not have a pressure guage they are readily available at any home depot for about $7. The watts brand with the red line needle is the best. 55-70 psi is the normal range for city water supply; anything higher should be investigated. Check the temperature of your water heater with a thermometer at the closest faucet. Most t & p valves will open if the water temperature rises above 140 degrees F. If it's too hot the thermostat will need to be replaced. This is easier and cheaper if you have an electric W.H. Gas is more difficult. Let us know what you find out. A relief tank will not fix your problem. Another thing you could try if it's too hot is to turn down the temperature on the thermostat.

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      • #4
        theron, the t&p valve will open due to thermal expansion. anytime you have a closed system, the heating of water will expand on a temperature rise. as cahndler noted the water meter has a backflow preventor on it. therefore the thermal expansion can't get back out to the city main. most pressure relief valves are set to open at 150#psi. not at 140 degrees.
        an expansion tank is basically an air bladder that acts as a shock absorber. the bladder will compress as the temp/ pressure goes up. as long as ther is no check valve on the cold inlet to the heater an expansion tank will work anywhere in the system.
        an expansion tank is required here in los angeles anytime a check valve is used on the heater or main. pressure regulator have a thermal expansion bypass incorporated into them. as long as the city pressure prior to the regulator is less than 150# the excess pressure will go back through the water meter and city main.
        there is a toilet ballcock that has a relif valve incorporated into it. as the pressure goes up, it will discharge into the toilet tank. i can't remember who makes it.
        one last issue. if any fixture drips or runs, a pressure increase will not occure. of course in a tight system, a pressure increase will occure.

        rick.

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        • #5
          I have a water pressure gauge on the water heater drain. The pressure is usually between 70-100, with a spike of 160. The instructions for the expansion tank say to check the pressure with a faucet open, then charge the tank to that PSI, which in my case it falls to about 60. I thought that the static pressure of 70-100 was pretty high. Should I install a pressure reducing valve? I am replacing the 1/2" pipe with 3/4" in the areas I can get to. I am going to leave the gauge on the tank overnight to see the peak psi.

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          • #6
            chandler, i would install a pressure regulator and set it to approx. 60-65 psi.
            do youself a favor and don't oversize the hot water system. you will end up with alot of wasted water when you have to run the hot water faucet at the far end of the house to remove the cold water from the system. try to stay away from a hot water loop, circulating system. if you do try to install a high water thermal loop. it's pretty basic and will work woth no pumps and no power. there will be next to no noise or wear.

            rick.

            Comment


            • #7
              I turned the temperature for the heater down to about 115-120 to try and limit blow off from the T&P valve a while ago. The problem with the placement of the tank is that the house is a old new Englander with a basement hight of about 6 feet, and the water heater is between the washer and dryer in a corner. If I put the chamber with the tank, it's actually obstructing the washer/dryer. Thats why I wasn't sure if the tank had to be that close to the heater or just anywhere between it and the backflow preventer, where I could put in out of the heavy traffic area. The spot I want to put the chamber is about 6 feet away from the heater. All the plumbers I ask in passing at work said the chamber is a must on a closed water system.

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              • #8
                that's correct. an expansion tank is a must on a closed system. infact in colder climate the heater will have to raise the incoming water temperature more. therefore more heat, more expansion. lowering the temperature or incoming pressure will give you more of a gap before you reach the 150#psi discharge rating on a relief valve.
                it's like a cars radiator and the overflow tank. as the car heats up, the water will expand and pressurize the system. at approx. 15# the radiator cap will open to vent into the radiator overflow tank.

                rick.

                [ 10-14-2005, 01:37 AM: Message edited by: PLUMBER RICK ]

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                • #9
                  So I should install a pressure reducing valve and its OK to locate the expansion tank before the branch? I appreciate the information guys, I didn't seem to have this problem before but I installed a new water heater and it started up. I had a guy tell me it could be because of the heat traps that are installed in the inlet to the heater, he said they restrict pressure relief. But it is a closed water system that is real tight, I have no drips anywhere. He was the only one that mentioned the heat traps and everyplace I look tells you to add them if you don't have them. Thanks again!

                  Comment


                  • #10
                    chandler, those little heat traps are a pain in the butt. they can't seal 100% and they tend to go bad. they restrict flow and will eventually get stuck in the closed position. they also can rattle.
                    i would still put the expansion tank near the heater. you can add a tee in the cold and put the tank out of the way of your other appliances. remember that a shut off valve is not allowed on the tank branch. although those tanks will eventually leak. if it's for your own home, i would install a 3/4'' ball valve for the tank to allow for future service. remember if the valve is closed, the tank won't function. a pressure gauge on the branch would also be a good idea.
                    there are 2 and 4 gallon tanks. if there is room use the larger tank. it's based on heater size, btu's, and temperature rise.

                    rick.

                    Comment


                    • #11
                      The backflow device he has threw me off. That can also cause it to do that. I'm not used to working with those because in Kentucky we only have one county where i live that requires them and that wasn't until 2002. I looked in my code book and thermal expansion tanks aren't in there, they are not required in KY. For my personal education I know they go on the cold side right near the W.H., but what are the specifics? You mentioned installing it after the shutoff valve and within five feet i think. The correct orientation for those things is nipple up, right?

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                      • #12
                        In reguards to heat traps, I totally agree - absolutely a pain. I always use di-electric unions to ease installation and removal in the future. I usually use a threaded ball valve so that if it fails in the future it can be easily removed and replaced without worrying about completely draining the system. Unions also give you an advantage when you're soldering so the hot air has somewhere to escape to instead of being locked into the heater.

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                        • #13
                          Chandler35,

                          What is the incoming pressure from your water service?

                          the dog
                          the dog

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                          • #14
                            Properly supported, an approved tank for use in thermal expansion control can be installed at any angle. In the State of Illinois any tank that is not installed within 5 feet of the tank is considered illegally installed. You DO NOT want to install this before the valve to your water heater. If the valve for any reason is turned off then your expansion tank will no longer protect your water heater.

                            If you need to cut in a tee between the tank and shut off and then run a short branch to keep the tank out of the way that can be acceptable, providing the run to the tank is not excessive. It doesn't take that long to install it correctly.

                            By setting the air pressure in the tank to your static pressure you are protecting against real world expansion. If you know your water heater will never ever kick on when you are not running water then the pressure taken while a faucet is running is fine. But we all know that our water heaters do run and cause thermal expansion when no water is being used.

                            If you have static pressure of 70 to 100 then I agree with Rick. You need a reducing valve just after your main shut off valve inside the home. Adjust the reducer to 60 pisg and then adjust the air in your expansion tank to 58 psig.

                            The ballcocks designed to relieve thermal expansion have one major draw back. The lady of the house hears the fill valve running and she calls out a service tech who is clueless to thermal expansion. He tosses in a 7 dollar ballcock and drives off whistling dixie and the homeowner now has no protection against thermal expansion. For this reason this style of protection is strongly discouraged throughout the State.
                            Work hard, Play hard, Sleep easy.

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                            • #15
                              the shut off for the cold water supply is about 6" before the 90 down to the water heater. If I understand you right it would be acceptable to install a T between the two, run about a 8" pipe horizontally so the tank is out of the way and install the expansion chamber on to that? Also, the water meter/backflow preventer from the town supply is on a pipe that runs vertically. Is it ok to intall a pressure reducing valve vertical? I've read that it may cause them to wear faster. Once again, I thank you for the help. I hate to say that I'm trying to save alittle money because it's time to fill the old oil tank.

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