Water heaters do condensate at times.
I had an AO Smith GCV 50 300 ProMax 50 gal gas water heater installed last weekend. There appears to be a minor leak under the bottom lip on the back side of the tank opposite the burner. Plumber returned mid week and explained it was condensation between the inner tank and the insulation and would disappear over the next several weeks. The leak appears to be less now, maybe 1 oz or less per day. Is this normal?
Thanks in advance for your advice.
Water heaters do condensate at times.
When you say condensate are you referring to the Flue condensate from the burner gas or condensation on the exterior of the inner water tank?
Is this going to rust out my tank prematurely?
I'm referring to condensate...take your pick as both apply in your case. It can cause a tank to fail prematurely. I'm not saying yours will. You can read about it in your owners manual.
The more you drain the WH, the more the cold water in the tank can cause condensation. Also, when the burner first turns on when the tank is cold, the moisture produced when the gas is burned can condense. Once things get hot enough, it stays as vapor all the way out the flue. If the flue isn't adequate, you might be getting some spillover, too. One good test is with a smoking candle or cigarrette - see if the smoke is sucked up the flue while the burner is on. If it is lazy or backdrafts, you need to address that.
Important note - I'm not a pro
Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014
Condensation occurs when moist air contacts a cool surface, which is below the dew point for the amount of moisture in the air. The only place condensation should occur in a water heater is in the flue when the heater is initially filled with cold water. The combustion gases will condense water which will drip on to the burner causing a "sizzling" sound. After that, the water entering the heater will be partially heated on its way to the bottom of the heater, so it should never cause condensation. Besides that, the insulation around the tank will keep any moist air away from the tank. One property of a small leak in a metal tank is that it can "rust over" and stop, at least until the rust spot gets larger. I have removed the insulation from many tanks which failed because of leakage, and some looked like they were shot with a machine gun because there are so many "old" rust spots on them.
Licensed residential and commercial plumber
Sounds odd to me. I wouldn't expect any tank surface condensate to last for long once the tank reached temp. The only way I could see actual surface condensate posing such a problem is in a humid room with the tank being rather cold to start and sitting like that for a day or two before any heating was done. (HJ's already well covered the flue gas condensate of a cold tank.)
Here's the problem: "condensate" in the insulation requires air movement to form, you need relatively humid air to come in contact with a surface at or below the dew point. But there isn't all that much water in any given volume of air that can condense, so it would take a lot of air flow in this very restricted space for that much condensate to form in the insulation. After the tank heats up the inside wall temp is WAY past the saturated air temp, so the water will begin vaporizing easily with any air movement. So if it were really "condensation" on the tank walls it would tend to remedy itself as quickly as it occurred.
Perhaps the installer leaked a lot of water into the insulation during the install... With little air flow in the insulation, it could take a while to dry out. Of course, some thread leaks or pin hole leaks in otherwise "good" vessels will seal themselves off as well, but are likely to bite you later.
However, I wouldn't put any faith in this being just condensate or installation water until I had carefully checked all fittings/projections off the tank to make sure none were leaking water. There are a number of threaded connections on tanks, and threaded connections are common sources of leaks.
Of course there could be a pinhole leak leak in a seam weld, etc. Since it is insulated and jacketed the only way to know is by deduction. If it keeps dripping from the insulation and you can't find a leak in any projections/connections, then an actual hole in the tank is likely and you will want a warranty replacement.
I'm assuming based on your description that this isn't a simple T&P valve drip (typically caused by the lack of a thermal expansion tank.)
" water entering the heater will be partially heated on its way to the bottom of the heater, so it should never cause condensation."
WTF????????????? LOL Electric heaters can condensate also......they dont have a flue.
I'm going to add two links to service bulletins. One gas and one electric. Please read them before anyone steps off the deep end and responds to my post.
Last edited by Hackney plumbing; 04-01-2012 at 05:14 AM. Reason: add links to keep the peace and to share knowledge.
quote; the majority of nonleaker returns
Have you EVER returned a leaking water heater to the manufacturer? The only thing I ever send to him is the rating plate with the serial number. The heater goes into the scrap heap. NO ONE looks at it or tests it. They do not explain HOW the damp air gets in contact with the heater's exterior when the insulation is bonded to it. It looks like a bunch of "engineer speak", with little relevence to the real world.
Licensed residential and commercial plumber
HJ in a humid climate condensation problems are compounded. While I agree the foam insulation has helped in very humid climates they can still sweat. Remember you live in a fairly dry climate......here you can almost drink the air on alot of days.
OK...everyone calm down. We all know that there can be condensation on the BOTTOM of a gas tank, especially on first start up when the tank is "ice cold" so to speak. In winter, if someone flat runs the tank out of hot...filling a bath or something, the incoming water is not going to get warmed up much as it goes towards the bottom
NOW....the OP here described a drip in an area that I would not immediately suspect as condensation, so I don't know if we have answered his question. I hope if the issue persists, he gets another plumber to look at it.
I still don't know what is causing the small leak. I did try the smoke test and the flue draws well, no visible condensation in the hood on top of the heater. I will wait another week or 2 to see if the leak dissapears and if not will call the plumber who installed it back. Thanks to all who expressed their opinions.
Adding to the condensing flue gas, it will happen in the flue within the tank as well when the tank is fully cold. I've directly observed the drops. It is more obvious on the top of the chamber itself, but the flue pipe will also produce droplets at least in the lower sections. (It's a fairly standard partial condenser configuration where the gas velocity is not so high as to entrain the liquid drops out the top.) Until the flue wall temp exceeds the saturation temp of the flue gas this condensation will occur.
I don't believe "condensate" is a proper verb. It is a noun. In this case "condensate" is being used as a verb to describe the condensation occurring on the outer tank surface. It's a new usage form that seems to be creeping up as a way of describing the situation in fewer words, but since it is already a noun it doesn't sound right. One could use the verb dew or sweat/perspire or refer to it as dewing or sweating but these verbs often imply specific mechanisms: sweating carries the connotation of liquid emerging onto a surface from within, and dewing is associated with cooling from radiant heat loss. There is probably a better verb to replace this use of condensate, but I can't think of it at the moment.
Had an intern engineer once who kept putting a superfluous "tate" at the ends of many verbs, particularly "orient." He was a sharp guy though...a bit quirky, but bright.