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Thread: New water heater, existing water softener, expansion tank needed?

  1. #1
    DIY Junior Member dhancock's Avatar
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    Default New water heater, existing water softener, expansion tank needed?

    Good evening folks, I just found this site this evening and I have found a lot of good information. I have been searching through the forum to find an answer to my question but after an hour or two, I didn't find one so I thought I would ask.

    I am looking to replace our water heater which is about 12-15 years old and seems to be on it's last leg. Anyway, in doing some research, I have seen the need for expansion tanks in certain cases. We have a well and a pressure tank, then water goes to a water softener and then to the water heater. I don't see any type of valve that would limit back-flow.

    My question is, does the water softener produce a closed system?

    We have had no problems with the TP valve being activated or any cracked parts or replacement of components on the water softener, which could indicate too much pressure. Since I am going to the trouble of installing a new water heater, I feel I should install an expansion tank if it is needed.

    Please excuse my ignorance but I didn't even realize there was any such thing as an expansion tank until tonight.

    Thanks for any help you might be able to give.

    Darin

  2. #2
    Illinois Licensed Plumber SewerRatz's Avatar
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    Illinois revised their code recently to require a expansion tank to be installed in all new water heater installations and replacements.

  3. #3

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    That is a great question and I can give you some limited help as I am not a water treatment system expert, there is at least on on this forum however.

    First off, the well tank is not designed to be an expansion tank but it will help you in this situation. Since you have a well I am assuming that you don't have a backflow preventer valve. Normally when you have a backflow preventer valve as required by many water companies these days, you need to add an expansion tank to the hot water heater.

    There is another issue concerning quick closing valves like the ones on clothes washers for example. They require an anti-hammer device to be installed nearby.

    Hope this helps but I don't think you will need one. It is always best to contact your local code department to ask if they have any special requirements.

    Also, you can install an expansion tank if you would like to regardless of whether or not one is required.
    http://www.inspectpa.com/forum/forum.php
    My answers are based mostly on the ICC codes. Advice given is my personal opinion and every person performing work should acquire a permit from his/her jurisdiction and get the work inspected. My opinions are not directions to follow for DIYs or professionals

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    Illinois Licensed Plumber SewerRatz's Avatar
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    AS Jar said it would not hurt to install one, and they are not all that expensive.

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    In the Trades Gary Swart's Avatar
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    An expansion tank is needed when there is a check valve or back flow preventer in the incoming water supply. Most frequently this is in a city water supply when a pressure regulator valve is installed. A PRV has a check valve built in. What happens is water expands when it heats. When there is a check valve in the supply system, this expansion has no place to go so it raises the pressure in the water heater and pops the temperature/pressure relief valve on the water heater. If there is no check valve, this expansion is easily absorbed back into the city water main so there is no need for an expansion tank. I do not know if a water softener has a check valve or not. I have not read any comments by softener experts about them so my gut feeling is they do not. If your well pressure tank does not have a check valve, then I would assume you do not need an expansion tank. True, they are cheap enough (around $50) but it would be a waste if not really necessary.

  6. #6
    Moderator & Master Plumber hj's Avatar
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    Default softener

    A softener does not create a closed system, and the storage tank acts as a large expansion tank. Requiring an expansion tank on every system is using a shotgun approach to a specific problem. It is the same reason everyone has to pay for the FVIR burner system because a few idiots were able to blow themselves up and/or burn their houses down.
    Last edited by hj; 01-12-2009 at 04:38 AM.

  7. #7
    Illinois Licensed Plumber SewerRatz's Avatar
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    Reason they want an expansion tank on all new and replacement of water heaters is that many cities and villages been changing out the meters and yokes. the new meter yokes have a built in duel check. Of course most of the municipalities fail to inform the home owner they need an expansion tank after the fact.

  8. #8
    In the Trades Gary Swart's Avatar
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    Are there no exceptions when the home is on a well? I do understand the logic of requiring them on homes connected to city mains.

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    Forum Admin, Expert Plumber Terry's Avatar
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    Are there no exceptions when the home is on a well?
    Most wells have expansion tanks.

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    DIY Junior Member dhancock's Avatar
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    Thanks for all of the good information. I finished the basement about 3 years ago and the inspectors were out to take a look at my work about 4 different times. They took a look at the water heater setup and they didn't mention anything about our county (or state) code requiring an expansion tank.

    The cost of the tank would not be an issue but where I would put it would cause some problems. The pressure tank, water softener, and the water heater are all setting right next to each other so I would have sort of difficult time even getting even a small 2 gallon, or so, tank in there.

    I may still give the building department a call just to make sure one is not required.

    I watched the video on here with the exploding water heater, and having such an old water heater (with a less than perfect TP valve I'm sure) has made me sort of nervous.

    I will keep you posted on what I find out. Thanks a lot for your information.

    Darin

  11. #11
    Retired Defense Industry Engineer jadnashua's Avatar
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    My local building department requires both an expansion tank, a vacuum breaker, and a tempering valve on all new WH installations, or replacements. Just depends on where you live.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  12. #12
    Master Plumber Redwood's Avatar
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    Quote Originally Posted by dhancock View Post
    I watched the video on here with the exploding water heater, and having such an old water heater (with a less than perfect TP valve I'm sure) has made me sort of nervous.
    There are a number of things way beyond the expansion tank that would have to occur to launch a water heater like the video.

    But yes water heaters are serious business!

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