Leaky DHW tank?

michael_15

I've got a reasonably middle-aged (3-5 years?) DHW tank in my basement.

Whenever I turn on the hot water tap, the water starts to spit some air, but only for about 3-4 seconds, and only right as the water is getting hot. That is, the water comes out fine while it's still cold and presumably pushing the water that was sitting around in the pipes out, but as the water starts to get warm, it spits. Once it's hot, it doesn't spit anymore.

I've decided (perhaps incorrectly) that this means something is going on in the locale of my DHW tank. However, I can't figure out what that is. A leak? Air is getting in somewhere, but there's apparently no water getting out, because my water meter's little triangle doesn't budge when the taps are off and there's certainly no water coming out of the basement. . .

I'm just worried that this is some sign of a water heater on its last legs, and that any day now I'll come home to a flooded basement.

Seeing that I already have steam heating (and hence a boiler), does that make it more economical to switch to indirect DHW in the event that the tank needs to be replaced? Or do high-quality indirects use their own boiler/heat source?

-Michael

Steve Paul

spitting faucets

The air that is being discharged from the hot water faucet is most likely because the water being heated is giving up the air and gasses that are disolved in it. Ever notice that a glass of water when left to stand around developes bubbles clinging to the inside wall of the glass? This is whats happening to your hot water. If you are on a well, it can be even more severe than on city water. And yes to your idea of using your boiler to power an indirect water heater. It would be the most economical replacement over time.

Larry Weingarten

anode rods...

...produce gas as they protect the tank from rusting. The "spitting" you have is usually more common when one has been away for a few days or more. The gas then builds up in the tank. Softening the water increases gassing. Less active anodes are available. Adding a vent on top of the heater is a possibility too, but they tend to lime up. Is it mainly a problem first thing in the morning?

Yours, Larry

michael_15

interesting

So if it's the anode rod producing electrolysis (and hence combustible hydrogen and oxygen gas), then in theory I should be able to attach a balloon to the end of my faucet tap when it's spitting, resulting in a balloon half full of water and half full of gas. Then, if I skim off the gas into another balloon and put a candle to that balloon, it should cause a fairly loud explosion. . .

Which sounds pretty fun.

I suppose that, if it doesn't explode, then it must just be water gassing out when heated, but if that were the case I'd probably expect the same behavior from my other DHW tank (I have two). Perhaps that tank just has a less active anode...

You're right that this is an issue every time I let the water go cold, so first thing in the morning, and after I come home from work. Should I be giving my anode rod a quick peek to see if it's almost gone?

No water softeners, but if my memory serves me correctly, the extremely hard water in my neighborhood would speed up the electrolysis as well.

Thanks,

-Michael

STEVE N

I agree

I agree with Steve, but I do have a question. Are you treating the water for sulfer? If so they use an air release tank with a vent on top. If the vent fails, it will not release the air and it will end up in your domestic water system. Just a thought.

Steve N

michael_15

nope, no treatment of any type.

straight from the city into the hot water tank.

I'm still looking to collect some balloons to check for electrolysis. I'm such a pyromaniac.

-Michael

Larry Weingarten

I suppose I should not admit...

...to having tried the balloon test. No glory ;~( Perhaps the "air" was too humid. In a balloon I wouldn't expect much of a bang as it isn't tightly constrained. Anyway, that might not be a valid test. I would look at the anode to see if six inches or more of the core wire is exposed. If so, you need a new anode. Try either a resistor type magnesium rod, (Rheem) or a zinc/aluminum rod, usually used for odor. Or an air vent!

Yours, Larry