Water heater leak troubleshooting for dummies

[T.G]

Originally Posted by forgop

Never had a hot water tank issue before. Small stream of water coming from the bottom of the tank. I shut off the gas and the supply line. The supply line shows visible condensation, but no actual drips. When shutting off supply line, leak from bottom stops. Therefore, I've eliminated that it's a hole at the bottom, but somewhere in the supply to the tank. There's no physical evidence of a leak, so if the leak is actually concealed inside the tank enclosure, is it pretty much in need of replacement?

I've thought about going with tankless, so I don't know if this is my sign or what.

Your diagnosis, or at the very least your explanation, makes very little sense.

Residential water heaters are just big tanks w/ a few pipes in/out and heating elements or, in the case of gas fired, a burner, plate bottom and exhaust pipe that runs through the center of the tank. There is no intricate piping system. If shutting off the supply stopped the leak, it's probably because you've eliminated the pressure supply. If you were to introduce air into the top of the tank, you would probably would have water coming out the leak point at the bottom again.

Here's a cutaway of a residential tank-style water heater:


As you can see, there really isn't anything there to leak except for the tank, and if it's leaking, it's probably a gonner. The older the unit is, the greater the likelihood of it being a leak in the tank, especially if the sacrificial anodes were never serviced (if equipped with them, not sure if all gas fired heaters have them).

Tankless are great, but they are expensive. The main thing will be matching up the desired temperature rise at the needed flow rate as you don't want to get one that is too small and incapable of heating enough hot water when multiple hot water valves are opened (say a shower and a sink or clothes washer). I would recommend looking at Rinnai brand for a tankless, they seemed to be the best rated and featured when I last looked into this, although things might have changed since then.

[markem]

It makes some sense that your tank might not leak with the supply turned off. It is possible that a partial vacuum is forming within the system that is just enough to keep the (what seems to me) small leak from occurring. Open a tap and see if it still leaks. Most likely will. Either way, looks like the tank is shot.

What I have read on tankless is that it is nearly impossible to recover your costs, especially on a replacement system since idea placement is likely impossible. However, it is always best to get several places to come out, give you an estimate and discuss the options. We expect our 80 gallon tank to not last more than 3 more years as it is 11 years old (although we do regularly flush it and have little if no sediment).

[Thaplumbr]

Sounds like a pinhole in the tank from the information you've given, when the supply valve to the tank is open and no fixtures are being used, there is standing pressure on the tank, in my neighborhood, we typically have about 70 psi from the utility, also this time of year you will have condensation on the supply line if its not insulated!
Just my
Leroy