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Thread: Opinion on expansion tank installation. Picture included.

  1. #31
    Retired Defense Industry Engineer jadnashua's Avatar
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    If you don't have a closed system, you don't need an expansion tank. Many homes have an open system, so any expansion has free access to the whole supply system - you'd never see a pressure increase as it would dispurse throughout the entire system feeding your house and neighborhood. BUT, exactly for that reason that water could get pushed back into the supply from a house, and it could have gotten polluted in the house, many locations are now routinely installing a check valve in or at the water meter turning those once open systems into closed systems. So, you could have been living there for decades with no problems, the utility company does some 'routine' work on your meter, and now suddenly you have a closed system, and things leak because of the expansion and resulting pressure increase. If you have a leaky valve (say a toilet valve or anything that drips a little), that may be large enough to relieve any pressure buildup. But, if you're good about maintenance and don't have any leaks, since water doesn't for all practical purposes compress, it will expand and create increased pressure. This will often trip the T&P valve at the WH. But, it might just burst a weak supply hose to the toilet, washing machine, or a sink. That's the thing...those items are not designed to be stressed by high pressure on a periodic basis...an expansion tank is.

    So, while you may get along quite fine without one, the circumstances could change quickly, and you need one.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  2. #32
    DIY Senior Member SteveW's Avatar
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    Yep, get the part about open vs closed systems.

    The question is still: why does it seem like now (like the last 10 years?) there is more of a concern about thermal expansion?

    I never heard anything about this 10 years ago. Was it happening but people didn't recognize it?

    Or has something changed, like more check valves being used? Or water companies using higher pressures, leading to more of us needing PRVs?

  3. #33
    General Engineering Contractor ballvalve's Avatar
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    Quote Originally Posted by master plumber mark View Post
    Watts sells expansion tanks for a profit and a living and have a vested interest in telling the public that you cant live without them....... but yes you can....

    Their are literally a hundred million homes without them in this country that have worked perfectly fine for decades and decades... and now all of a sudden the world is going to come to an end if one is not installed on your system..

    In this city alone their are literally tens of thousands of water heaters installed on the second floors of the homes without thermal expansion tanks.... all built around 1995..and after to this date..

    those plumbers ignored the thermal tanks but did install alluminum pans and piped the pan and the t+p line to the flooor drains in the room... they have mostly all worked fine till the heaters started leaking.....


    if you have dramatically high pressure you should consider one,, and also a PRV valve to kick it down to 70psi...



    Sometimes I have wondered which congressmen watts had to bribe to make thermal expansion tanks code...

    If you are not willing to service the system yourself, its just a matter of time
    before that Expansion tank becomes a liability when it gets waterlogged....

    also, those Watts pressure releif ballcocks scare the dickens
    out of me and I wont trust them...



    this is what a water heater looks like after 10 years of service in Indiana
    with no one ever flushing it out.....
    http://www.youtube.com/v/mjWDyaQGDiY...ram%3E%3Cparam


    thanks, I have been saying that here for a long time. Funny that redwood did not attack you for being low on grey matter for speaking the truth about this.

    And all toilet valves are pressure relief valves around 160 psi!

    And the utube is a POS saying the heater needs replacement each 6 years. It needs MAINITENANCE every year.

    Dont change your engine oil and just trade it in every 5 years would work too.
    Last edited by ballvalve; 05-28-2011 at 02:28 PM.

  4. #34
    Master Plumber Redwood's Avatar
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    Anyone that would think it is okay for a T&P Valve to dribble relieving the pressure from thermal expansion is either in the business of selling water heaters and wanting to increase his sales due to early failure of the water heater from metal fatigue and cracking of the glass lining increasing corrosion or short of the grey matter!

    That's my story and I'm sticking to it!

    I think the reasoning is sound in both cases.

  5. #35
    Retired Defense Industry Engineer jadnashua's Avatar
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    Many utilities are now installing check valves when retrofitting meters and on new installations. As areas are being built-up, to provide decent water pressure to all of the customers, many utilities are adding pumps, towers, and raising the pressures. This means more PRV's are being installed. So, yes, you could have lived there for decades with no problems...things change, you change with it, or suffer the consequences. Just because you've 'always' done it one way, does not mean that it necessarily still works and is the best way. Change with the times, or suffer the consequences...if you have a closed system, the accepted solution is an expansion tank. Live with it.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  6. #36
    DIY Senior Member SteveW's Avatar
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    Quote Originally Posted by jadnashua View Post
    Many utilities are now installing check valves when retrofitting meters and on new installations. As areas are being built-up, to provide decent water pressure to all of the customers, many utilities are adding pumps, towers, and raising the pressures. This means more PRV's are being installed. So, yes, you could have lived there for decades with no problems...things change, you change with it, or suffer the consequences. Just because you've 'always' done it one way, does not mean that it necessarily still works and is the best way. Change with the times, or suffer the consequences...if you have a closed system, the accepted solution is an expansion tank. Live with it.
    Again, I am on the same page as you - I am not arguing; I insisted on having an expansion tank put in when my WHs were replaced, even though several local plumbers seemed to think I was crazy.

    I heart expansion tanks!

    Just wondering why now the awareness of this problem. Your explanation makes sense to me - expanding neighborhoods, higher water pressures, and water companies that are using more check valves to prevent contamination.

    Makes sense to me.

  7. #37
    Master Plumber master plumber mark's Avatar
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    Default 6 years is a little short....

    actually , my buddy from DUNBAR PLUMBING made that video for me....

    and me and my buddy REDWOOD disagree all the time,,,,
    I dont take it personal...

    I would have probably stated 7 or 8 years between change outs..

    Yes , I do have a vested interest in installing water heaters....

    and I am going out right not at 8 pm to install a
    50 galllon PRO RHEEM.......

    and I am gonna install it in a pan,
    and I am gonna run the drain to the sump pump...
    and I will offer them a thermal expansion tank for another $150 dollars, but they will probably decline my offer becasue it
    sits right by the sump pit....

    and you dont want to know what I am chargeing them tonight....

    so talley---ho..........up, up and away I go.....

    .


  8. #38
    Moderator & Master Plumber hj's Avatar
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    quote; So - under certain circumstances, it appears that having some sort of thermal expansion relief (expansion tank or other mechanical device like the Watts pressure-relief ballcock, etc.) could potentially make it less likely for a WH to rupture.

    EVERY water heater MUST have an approved temperature AND PRESSURE relief valve, so a "thermal expansion relief valve" would be redundant. They release at a "safe" 150 psi,, but if you do NOT wish to install an expansion tank, you CAN install ANY pressure only relief valve somewhere in the system with a set point equal to your desired maximum pressure and it will discharge any time the pressure rises to the point. Which is EXACTLY what Watts "TERV" does.

    quote; And all toilet valves are pressure relief valves around 160 psi!

    Absolutely NOT true, and if the heater's T&P valve is functioning properly , HOW would the pressure get to 160 psi anyway?
    Last edited by hj; 05-29-2011 at 07:56 AM.

  9. #39
    DIYer, not in the trades LLigetfa's Avatar
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    Quote Originally Posted by hj View Post
    EVERY water heater MUST have an approved temperature AND PRESSURE relief valve, so a "thermal expansion relief valve" would be redundant. They release at a "safe" 150 psi...
    ...in theory, as long as they still work. When I took out my 10 year old tank, I tried releasing the TPR to break the vacuum and it was seized shut.

    Now, my system is not closed so any expansion would be absorbed by my iron filter precipitation tank so the only real risk was of a runaway flame boiling the water in the tank.

    My RO filter could also absorb some of the expansion.

  10. #40
    Master Plumber Redwood's Avatar
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    This link is a post that discusses pressurization cycles on a pressure vessel, and metal fatigue caused failure. Incidentally it is also in a thread muddied up with the rambling thoughts of a thick headed engineer...

    These engineers come and go but for each one that goes, we always seem to get another willing volunteer to take his place muddying up threads with their senseless wisdom....

    It is a "Strange Day Indeed" when plumbers start agreeing with their senseless ramblings....

    Pressure Cycling on pressure vessels is real and it does cause fatigue of the metal. Sooner or later the metal cracking or the damage to the glass lining from this flexing allowing corrosion damage to occur will cause a failure of the tank. An expansion tank will hold the pressure constant vs. the relief allowing it to fluctuate between the supplied pressure and the rated opening pressure of the valve. In the case of relying on the T&P as Master Mark suggests is okay this could make the minimum pressure cycle to be 70 PSI. Incidentally the pressure cycle on a jet airliner taking off at sea level and going to it's cruise altitude at 30,000' is only a 10.34 psi cycle and we can see the consequences in the linked thread.

    It's plain and simple Expansion Tanks Work!

    Instead of the tank going through pressure cycles and being subjected to metal fatigue and an early failure, the tank pressure remains constant. A relief valve can work, we have been through this discussion with BallValve, however it is not the best choice. An increase in pressure supplied or a failure of the valve can lead to a very high water bill without you ever knowing the water was flowing down the drain. These valves do not last forever, and someone is placing way too much value in a $50 valve over a $50 expansion tank. Even with a relief valve as proposed by our esteemed engineer friend a water supply system that has a supplied pressure of 40 psi would go through a minimum of a 35 psi pressurization cycle to the opening pressure of the relief ball valve with every heating cycle, incurring the metal fatigue and shortening its service life. Neither device protects against runaway heating, that is the job of the BTU rated T&P valve. With the price being equal and one having the ability to waste large volumes of water while subjecting the water heater to life shortening pressure cycles, it is like a no-brainer to me but that doesn't always work with engineers.

    The use of the Governor 80 Ballcock is remote from the water heater and is easily isolated out of the equation with shut off valves leaving no protection. In addition someone doing toilet repairs can easily not know what they have and replace this uncommon ballcock with a Fluidmaster 400A removing what little protection it afforded. We've been through that argument as well. There are many ballcocks that will not open at 160 psi as our esteemed engineer believes in his senseless ramblings above...

    Simply stated a properly installed Thermal Expansion Tank is the best available solution for thermal expansion.
    Last edited by Redwood; 05-29-2011 at 08:36 AM.

  11. #41
    General Engineering Contractor ballvalve's Avatar
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    Certainly expansion tanks work and reduce pressure flucuations - until they fail, and that is a definite. And homeowners dont give a whit about checking them while trying to keep up with all the other more obvious failures in life like a flat tire.

    A large percentage of homes in america do not have city supplies, and many that do, dont have a regulator. So before installing the bag in a can with no visible failure indicator, the plumber should evaluate the supply system. [many do not because they want that extra 200 bucks on the job]

    A sys with the ex tank, which holds pressure to lets say 70..... then a 100 psi relief valve... then the final solution the valve on the WH. Now you know when the ex tank has failed, if your 100 psi, 7$ valve drips.

    I do not advocate the watts ballcock. Seems a bit stupid. However, the screw on relief valve for a hose bib [the drain valve?] is interesting.

    The watts ballvalve-relief valve combo should be standard practice, set above the max accumulation of the ex. tank.

    The point about all toilet valves being relief valves is that the cheap plastic will blow at high pressure, long before the water heater tank.

    Why install a 10 or 15 year waterheater and 5 or 7 year ex tank? Give your customer a failure indicator.

    This has nothing to do with 'engineering' but all to do with common sense.

  12. #42
    Master Plumber Redwood's Avatar
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    Quote Originally Posted by ballvalve View Post
    Certainly expansion tanks work and reduce pressure flucuations - until they fail, and that is a definite. And homeowners dont give a whit about checking them while trying to keep up with all the other more obvious failures in life like a flat tire.
    You are absolutely correct! Most things do work until they fail! You're thinking expansion tanks fail far more often than they actually do. Properly installed and sized they have a long service life. In my own home I have an expansion tank on the boiler and water heater and am in my mid 50's. I can count the replacements of both on less than 1 hand...

    Quote Originally Posted by ballvalve View Post
    A large percentage of homes in america do not have city supplies, and many that do, dont have a regulator. So before installing the bag in a can with no visible failure indicator, the plumber should evaluate the supply system. [many do not because they want that extra 200 bucks on the job]
    The visible sign of failure for a thermal expansion tank is the T&P valve leaking a small amount of water. There is no visible sign of failure on a relief valve until you receive an enormous water bill for dumping water down the drain.

    A plumber should always troubleshoot the system to determine if an expansion tank is needed as well as other causes for a T&P discharge.

    Quote Originally Posted by ballvalve View Post
    A sys with the ex tank, which holds pressure to lets say 70..... then a 100 psi relief valve... then the final solution the valve on the WH. Now you know when the ex tank has failed, if your 100 psi, 7$ valve drips.
    Except you will not see the valve dripping as they are plumbed to a drain. Also your $7 valve is actually much closer to $50 or, more....

    Quote Originally Posted by ballvalve View Post
    I do not advocate the watts ballcock. Seems a bit stupid. However, the screw on relief valve for a hose bib [the drain valve?] is interesting.
    You did advocate it in the past. Your relief valve that screws onto a hose bibb or, drain valve is not useable for the same reason as the ballcock... It can be isolated by a valve and kept from affording protection to the water heater.

    Quote Originally Posted by ballvalve View Post
    The watts ballvalve-relief valve combo should be standard practice, set above the max accumulation of the ex. tank.
    I agree to disagree with you on this subject.

    If you want that in your home that is just hunky freakin dunky... Put it in! But I would not advocate that for a majority of sensible people it is a redundancy that is not needed.

    Quote Originally Posted by ballvalve View Post
    The point about all toilet valves being relief valves is that the cheap plastic will blow at high pressure, long before the water heater tank.
    Maybe... Maybe not... Did you engineer it?

    Quote Originally Posted by ballvalve View Post
    Why install a 10 or 15 year waterheater and 5 or 7 year ex tank? Give your customer a failure indicator.
    Again, your figures of failure on expansion tanks are vastly overrated...
    If you are experiencing expansion tank failures at this high a rate you should either learn what you are doing wrong on the installation. Or, stop hiring CraigsList Plumbers... Clearly something isn't right!

    Again the relief valve has no visible sign of failure, but the expansion tank failure will result in a small t&p valve discharge.

    Quote Originally Posted by ballvalve View Post
    This has nothing to do with 'engineering' but all to do with common sense.
    I agree! When are you going to get some?

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    Last edited by Redwood; 05-29-2011 at 06:14 PM.

  13. #43
    Master Plumber master plumber mark's Avatar
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    Talking What is a thermal expansion tank cost installed??

    yes, their is a possiblilty that a thermal expansion tank
    may extend the life of a water heater, a year or two...

    that is if it does not become waterlogged in 6 years or less.. and someone checks the pressure levels in them every year or so......(not gonna happen)

    we do offer them when we install a heater, but on average most everyone does not care to spend the extra money for a variety of different reasons.

    the larger thermal tank is worth about 60 bucks, ....what does everyone think is a fair price to install one while doing the installation??

    I offer them installed for $150....
    and another 250 for a prv valve....

    and their are places in town that attempt
    to get about $600 for both...

    we are getting on average about 10 years out of Rheem gas heaters in this area without the help of thermal tanks....with averge pressure rangeing around 80psi....

    very few people actually drain or clean out their heaters, and less that that number will ever check the pressure on thermal tank

    so....after about 9 years, with the lime buildup and sediment buildup inside the heaters.....the efficinecy of the heaters starts crashing...

    at what dollar amount does it all become a mute point???


    so what do people charge to install one at time of installation??



    come on....lets figure this out




    Redwood...I wish I were an einstein and could make up some fancy graphs
    showing some wiggley lines on it with the cost of the thermal tanks
    vs.. the drop of co-efficiency of the water heater after 10 years,,,
    divided by the ......mass of the ass of your old lady......
    taking showers every day.......

    then we could finaly get this questioin answered....

  14. #44
    Moderator & Master Plumber hj's Avatar
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    quote; in theory, as long as they still work. When I took out my 10 year old tank, I tried releasing the TPR to break the vacuum and it was seized shut

    And I suppose you had NOT tested it during those 10 years. THAT is the reason it is recommended that WE test the T&P valves on our customer's water heaters whenever we are in the building. They may not like it when it proves defective by either NOT opening, or not closing when the lever is released, but it will prevent a situation such as a "10 year old heater with a frozen T&P valve".

  15. #45
    Moderator & Master Plumber hj's Avatar
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    quote; BUT, exactly for that reason that water could get pushed back into the supply from a house, and it could have gotten polluted in the house,

    Just as the expansion tank only has to absorb a SMALL amount of water to eliminate thermal expansion pressure, the amount of "backflow" would be in the range of a few inches, and NO WHERE near enough to force "water from the house" back into the city main. The ONLY water which would be pushed back into the main would have been between the main and water meter and would NEVER even have been near the house.

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