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  1. #1
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    Home plumbing question...

    When one looks at their water heater...
    They usually see a 'pressure balancing tank' close by (that tank attached to one of the water pipes)...
    As I understand it: The purpose of that tank, is to allow room for the water to expand when the water heater heats it (warmer water occupies more space than colder water).

    My question:
    If one gets rid of their tank style water heater, and replaces it with a tankless...
    Does the water system still need the pressure balancing tank???

    THX in advance for thoughts...
    Appreciate it!
    GA-HVAC-Tech

    Your comfort, Your way, Everyday!

    GA's basic rules of home heating and AC upgrades:
    *Installation is more important than the brand of equipment
    *The duct system keeps the house comfortable; the equipment only heats and cools (and dehumidifies)
    *Cheap is not good, good is not cheap; however expensive is not a guarantee of quality!
    Choose your contractor wisely!

  2. #2
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    Unless your local codes say otherwise, Your house only needs it if you have a check valve on your city supply line. This is most commonly fond in your water meter, or anywhere after a check valve on any line really.

    Even the city water will warm up to room temperature after it enters your house and if you have a check valve installed then even that “small “ temperature increase is enough to put a large strain on your pipes.


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  3. #3
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    Quote Originally Posted by thatguy View Post
    Unless your local codes say otherwise, Your house only needs it if you have a check valve on your city supply line. This is most commonly fond in your water meter, or anywhere after a check valve on any line really.

    Even the city water will warm up to room temperature after it enters your house and if you have a check valve installed then even that “small “ temperature increase is enough to put a large strain on your pipes.


    Sent from my iPhone using Tapatalk
    Yes.

    Also check whether the water pressure reducing valve (PRV) has a thermal bypass. If not, it will act as a check valve. Even with a PRV with this feature, I've seen HWT pressure reliefs go due to a failed PRV.

    http://media.wattswater.com/ES-25AUB.pdf

    Regardless, I always add an expansion tank on cold water line when installing a HWT, no matter the type. They are cheap, burst pipes are expensive.

  4. #4
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    Thread Starter
    THX guys...

    Appreciate it!

    GA
    GA-HVAC-Tech

    Your comfort, Your way, Everyday!

    GA's basic rules of home heating and AC upgrades:
    *Installation is more important than the brand of equipment
    *The duct system keeps the house comfortable; the equipment only heats and cools (and dehumidifies)
    *Cheap is not good, good is not cheap; however expensive is not a guarantee of quality!
    Choose your contractor wisely!

  5. #5
    Join Date
    Apr 2004
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    MN
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    Oddly enough, Ive owned 4 houses throughout the years and rented 2 and none of them have had expansion tanks on the domestic water system. It's just not that common around here. Not sure why?
    A Veteran is a person, who at some point in their life, wrote a blank check payable to the United States of America for payment up to and including their life.
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  6. #6
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    Feb 2004
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    Most locals don't require them on well systems because the system has an exp tank that absorbs any expansion. The code for tanks is fairly recent.
    If HW tanks are replaced the code probably requires them.
    Give me a relay with big enough contacts, and I'll run the world!

    You can be anything you want......As long as you don't suck at it.

    If a person wants to create a machine that will be more likely to fail...Make it complicated.

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  7. #7
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    On Municipal water systems back flow preventers are now required so expansion tanks are needed. The expansion used to back into the mains!

  8. #8
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    Quote Originally Posted by pecmsg View Post
    On Municipal water systems back flow preventers are now required so expansion tanks are needed. The expansion used to back into the mains!
    I liked when backflo preventers were required on boiler systems. They can be nasty.
    I remember a company that would add glycol to boilers w/o backflo preventers. They weren't code at the time but glycol is poisonous. They pointed to the check valve in the water pressure regulator. But a lot of them don't work well and are not a positive shutoff.
    Give me a relay with big enough contacts, and I'll run the world!

    You can be anything you want......As long as you don't suck at it.

    If a person wants to create a machine that will be more likely to fail...Make it complicated.

    USAF 98 Bomb Wing 1960-66 SMW Lu49

  9. #9
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    Food grade glycol is your anti-liability friend. <g>

    PHM
    --------


    Quote Originally Posted by hvacker View Post
    I liked when backflo preventers were required on boiler systems. They can be nasty.
    I remember a company that would add glycol to boilers w/o backflo preventers. They weren't code at the time but glycol is poisonous. They pointed to the check valve in the water pressure regulator. But a lot of them don't work well and are not a positive shutoff.
    PHM
    --------
    The conventional view serves to protect us from the painful job of thinking.

  10. #10
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    Jun 2012
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    If you need glycol in a boiler, you do not want plain make up water! Small leak, after time, just water in system and freeze damage happens.

    Cheapish glycol makeup system: Well pressure/bladder tank plumbed into the make up PRV. Pressurize the air side to 60PSI or so and then pump the glycol makeup solution into the pressure tank. If it leaks, makeup solution is anti-freeze. Annual service to check status of makeup supply as well as service equipment. If it is a big leak, the system shuts down on LWCO (you do have a LWCO, right?)

  11. #11
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    Quote Originally Posted by Juan Madera View Post
    If you need glycol in a boiler, you do not want plain make up water! Small leak, after time, just water in system and freeze damage happens.

    Cheapish glycol makeup system: Well pressure/bladder tank plumbed into the make up PRV. Pressurize the air side to 60PSI or so and then pump the glycol makeup solution into the pressure tank. If it leaks, makeup solution is anti-freeze. Annual service to check status of makeup supply as well as service equipment. If it is a big leak, the system shuts down on LWCO (you do have a LWCO, right?)

    I once worked where boilers were about 35% of the service business. N.Ill and few had antifreeze. Maybe because automotive type was the only available until Dowtherm came around and later the propanol(sp) version. There is an efficiency loss with antifreeze. I think something like 10% but that's just memory.
    To help with the efficiency the solution only has to be down to like 10 degF just where it turns to slush if serious temp drop. Slush won't break anything.
    Give me a relay with big enough contacts, and I'll run the world!

    You can be anything you want......As long as you don't suck at it.

    If a person wants to create a machine that will be more likely to fail...Make it complicated.

    USAF 98 Bomb Wing 1960-66 SMW Lu49

  12. #12
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    Quote Originally Posted by hvacker View Post
    Maybe because automotive type was the only available until Dowtherm came around and later the propanol(sp) version.
    ... Polypropylene.

    At the risk of venturing beyond open forum information, this is a great read for those who service hydronic systems: http://msdssearch.dow.com/PublishedL...038010e417.pdf

    It outlines burst vs freeze protection, which your full post touches on. I should probably read it again for a refresh as winter continues to take hold.

  13. #13
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    Quote Originally Posted by Juan Madera View Post
    If you need glycol in a boiler, you do not want plain make up water! Small leak, after time, just water in system and freeze damage happens.

    Cheapish glycol makeup system: Well pressure/bladder tank plumbed into the make up PRV. Pressurize the air side to 60PSI or so and then pump the glycol makeup solution into the pressure tank. If it leaks, makeup solution is anti-freeze. Annual service to check status of makeup supply as well as service equipment. If it is a big leak, the system shuts down on LWCO (you do have a LWCO, right?)
    (Sorry GA. We're are a little beyond your original, presumably, domestic water heater question... You know how threads go. )

    An oversized expansion tank does make for a cheap make up water solution. Though, I question the 60 psi air side charge. Particularly in the case of a typical 12 psi minimum water/glycol pressure system...

    I would like to suggest that it is best to still charge air side at 12 psi, but then pump up the loop to 20 psi (or more) with fluid. This will result in a residual amount of stored fluid in the ET that can be pushed back into system in the event of a leak. Once at or below 12psi the ET is empty again, with the LWCO shutting system down in the event of further fluid loss.

    The above setup is often used in closed loop geo systems, along with small hydronic heating.

    If you are starting with 60 psi in air side, you will not get a residual amount of fluid in ET until system pressure exceeds 60 psi. This would be considered an unnecessary high pressure and maybe above some boilers MAWP. Even in the case of having an ET and PRV setup dedicated to MUW, as you suggest, 60 psi is not required and will limit the residual fill capacity.

    Now why 12 psi and is it always 12 psi? Mmmm I've probably covered more than we should be in open forum.

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