[jlisenbe]

In the case of an expansion tank, will it simply fill with water after years of use once the air inside gets dissolved into the water, much like what happens in the pipes intended to prevent water hammer?

Just a question.

[Hometec]

Gee! I haven't seen any mass failure of water heaters in either my area or the entire West Coast of Florida. Must be your water huh?

Hi Tom,
I am glad that there have been no water heater problems in your area, and hope that there are never any. However, when the water heater exploded in an Oklahoma school, killing a teacher and six students, the sky indeed had fallen for the loved ones and survivors. Please realize that the code is not established on how many things go right, but on what has and could go wrong. What could go wrong is that some jack-leg repairman, or a homeowner with a lack of common sense, could plug the leaking t&p. That type of ignorance of water heaters cannot be attributed to the water here in NC, but probably comes from drinking water from non-closed systems. :) The fact is a water heater has the potential to explode. Everything that a plumber can do to comply with the code should be done to limit that potential.

If you don’t put an expansion tank on a CLOSED SYSTEM, and a water heater explodes for what ever reason, you’re going to be the whipping boy. The Insurance Company is going to subrogate against you and the State Board will take your plumbing license. If people are killed, you will be blamed by the friends and relatives and you may as well move out of the state. Further, it will make no difference what you believed before it exploded, you will carry the doubt and guilt for the rest of your life.

Now, you keep bringing up NON-ClOSED SYSTEMS, which I have not elaborated on. The reason that our code requires expansion tanks on non-closed systems is because they are not going to stay that way long.

Expansion tanks might not prevent water heaters from exploding that have frozen t&p’s, but they buffer the thermal expansion on the closed system, The water heater itself expands and contracts, and that this process is what cracks the glass lining and allows the water to deteriorate the metal. Therefore, it is a given that an expansion tank can buffer the thermal expansion.

And you know this for a fact, how?
It's just got to be something I n the water up there the robs homeowners of good sense. We don't seem to have that problem here.

The following is comes directly from the A. O. Smith Corporation, the largest w/h manufacturer in the USA.

Thermal Expansion as relates to water heaters/boilers is an increase of the volume (or space taken up) by water within the unit, caused by heat. In other words, when water heats it expands or takes up more space. The excess volume of water, because of pressure created, will flow to the place of least resistance. Unless a faucet is open, generally this would be into the cold water pipe (this is why sometimes the pipe above the cold water inlet is warm for a few feet). In a closed system, the excess volume of water has no place to go and builds pressure within the unit. When the pressure reaches a certain point, a safety device called a temperature and pressure relief valve (T & P) will open relieving pressure. Over time (perhaps as little as months or as great as years) this increase and decrease in pressure, without the protection of an expansion tank, can weaken the tank causing premature failure. Generally what is seen is a drip to a stream of water from the T & P that continues until pressure is relieved. Most often reported is a cup to a few quarts of water a day - to every few days. And, usually the release of water is greater after a large amount of hot water has been used - like taking a shower. These symptoms may be evident immediately upon installation or months to years down the road, or even not at all until the water heater fails.

I take no offense at your remarks, Tom. My skin has thickened over the years of dealing with the public and very persnickety plumbing inspectors. However, I hope that you see the benefits of expansion tanks on non-closed systems since they are likely to become closed.
C. H.

[speedball1]

In the case of an expansion tank, will it simply fill with water after years of use once the air inside gets dissolved into the water, much like what happens in the pipes intended to prevent water hammer?

Just a question.

And when the expansion tank loads up with condensate it's the same as if there were no tank there at all. Regards, tom

[Hometec]

In the case of an expansion tank, will it simply fill with water after years of use once the air inside gets dissolved into the water, much like what happens in the pipes intended to prevent water hammer?

Just a question.

Hi jlisenbe,
I confess that I don’t know about air being dissolved into water, but expansion tanks do fail. The primary reason that they fail or fill with water is the air bladder or Strader valve develops a leak. Of course, the tank can also develop a water leak. Air dissolved in water contains approximately 35.6% oxygen compared to 21% in air, so it may not be an issue. However, I believe that water has to boil before air dissolves in water, and that should not occur inside of the expansion tank if it is installed on the correct side, the cold water source. I have seen expansion tanks on well systems that were so old the manufacturer was no longer around, but they were still working. However, I heard that there were some bad problems with expansion tanks in Myrtle Beach, SC. Those problems were due to poor manufacturing. Hope that helps.
C.H.

[speedball1]

I hope that you see the benefits of expansion tanks on non-closed systems since they are likely to become closed.

I believe what I'm fixing on is

on non-closed systems since they are likely to become closed

. That's quite a assumption, how did you arrive at it?
I agree that a expansion tank's necessary when the system's a close onr. But to charge a customer for a installation based on a maybe you'll install a sprinkler and be forced to install a backflow preventer Down here we don't install a appliance or a fixture based on a "MAYBE. Cheers, Tom

[Hometec]

[quote] That's quite a assumption, how did you arrive at it?[quote]

As I previously stated, but I don’t mind reiterating, the code requires expansion tanks on all water heater installs in our state. Closed systems, we agree on. Expansion tanks should be installed on non-closed systems because the code requires it. The reason is because there is a massive effort to make all potable water systems closed. The premise of this effort may be because of the contamination factor from home. However, another reason may be Homeland Security. Instead of a million places where a terrorist can hook a hose to the potable water and send anthrax throughout the neighborhood, maybe they narrow it down to a few access points by installing check valves everywhere. It doesn’t really matter why when the code requires it. The only choice then is if you intend to comply with the code. BTW, I do not charge labor for installing expansion tanks. My w/h install labor price is the same as it was before expansion tanks were required. The motive is not money, but code compliance.
Thanks,
C.H.

[jlisenbe]

HT, I am more familiar with wells. The air in a pressure tank (non-bladder) will dissolve into the water (due, I suppose, to being under pressure) within a few months, and we are talking about a fifty or sixty gallon tank. However, you mentioned that these expansion tanks have a bladder in them, so that would answer my question.

As usual, I am enjoying this exchange. It brings out a lot of truth when these experienced guys debate these issues.

[speedball1]

Thank you Hometec for your explanation. I completely understand your reasoning.

The reason is because there is a massive effort to make all potable water systems closed.

And will this "massive effort" be retroactive? Because it hasn't got here yet, ( we're still waiting) How can I word this? I have had experts on this page who were dtickers for code. if it don't agree with my code it ain't right!! Our answers don't always follow code. We are more about getting the asker repaired This is not to say we promote dangerous plumbing practice. It means if we have a asker with a 100 year old house with "S" traps throughout with a drainage leak we don't attempt to force him to upgrade his drainage to vents and "P" traps. We tell him how to fix his leak. That's what this page is all about. The asker is king and our goal is to get his problem fixed the fastest easiest and cheapest way that he can do himself. Of course when we lay out a plan we follow code but when we answer we kind of tiptoe around it. I don't want to hear, "This is't code in my area". I want to hear, "this is how to repair your problem". Regards, Tom

[Hometec]

I don't want to hear, "This is't code in my area". I want to hear, "this is how to repair your problem". Regards, Tom

Hi Tom,
I apologize for misunderstanding your intention with this site. I read disparaging remarks about licensed plumbers installing expansions tanks as if they were attempting to bilk the public , etc. I can understand your information about s-traps, faucets, and the like coming from the perspective of helping a homeowner with plumbing repair. No one ever died from an exploding faucet or siphoning s-trap. However, when you tell someone to do something that could cost them their lives…maybe you ought to explain the danger as well. I apologize if my posts offended you. Lots of luck with your site.
C. H.

[spudwrench]

I have been a plumber for thirty years. For the record the higher the water pressure you have in your house the more problems you will have with your plumbing. It is always looking for the weak links in your system. I always had more service calls in the parts of town with higher pressure. If you have a check valve in your meter at the curb, you will have too high of pressure in your house. You will need a expansion tank to prevent your pressure from climbing. It is for protecting the whole plumbing system. Not just the t&p valve from opening. High blood pressure may not be what kills you one day but if you want to play the odds you take care of it. For the plumber that never saw a t&p fail, well I have been to three service calls were the water exploded. I don't think these so called plumbers care that they install waters heater wrong and leave your house with 130 psi on your weak plastic ice maker line.

[massplumber2008]

Hi Spudwrench

Nice post, but look at the dates of this thread and you'll see that it is back from 2008. Always check dates before posting, OK (and make sure the question hasn't already been properly answered)?

I hate to see anyone write that much and have it go unappreciated! :)

Have a great day!

Mark

[TomFMB]

I am on city water. The city does NOT have check valves at meter and I do not have a check valve either. The Thermal Expansion Tank is releasing water back out... then brings it back in when pressure drops below city pressure. Consequently I am paying for the same gallon of water over and over. We isolated this, with a licensed plumber, to the Thermal Exp Tank. There is a T&P in place as well and drains into a try if needed and out of the house. Electric water heater. I am planning on putting in a check valve, but city pressure is not all that great to begin with and I have been told anywhere from 6-10 psi drop. Would you add check valve or remove thermal tank? Thanks

[massplumber2008]

Hi Tom...

I would remove the expansion tank to start and watch the little red dial on the meter. I seriously doubt the issue is with the expansion tank and suspect that you have a leaking hot wtaer pipe. Check out the answer I posted at the question you posted at the main plumbing page and leave your answer or any questions back at that thread. Thanks...

Mark