Hot Water Tank Rumbling

I moved into a new house almost a year ago. From the first day that I moved in, the Hot water tank would rumble. It's certainly an older (gas) unit and will need replacement in the near future, but I'd still like to try to figure out variouis reasons that it might be rumbling.
I had first assumed that it could be sediment in the tank, so I drained it, but didn't really get anything coming out during the drain.
The drain may have helped some, but it's tough to call. Since the drain, over time, it has lessened. It used to rumble when you'd open a tap or fill a bath, but it seems not to do it at those times so much now. I just heard it rumble when the dishwasher was running.
Any ideas on the various causes that could be at work, causing the rumbling?
I think I may plan to go to a tankless (gas) Hot Water Heater when this dies, but I'd still like to try to figure out what's going on to cause the rumbling in the mean time.
Thanks,
Danny
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Rumbling can be caused by calcium build up in the tank. I had one do that.
When you drain it is important to remove the drain plug completely, connect a hose and then fill and flush with water again. The drain plug is pretty small and the straight hose connection will let more particles out.
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This is probably sediment build up in the tank. The reason it didn't all come out is that the valve constricts the opening. There are a couple of things you can do for your water heater to make it function better.
Replace the drain valve with a full port ball valve. When open this valve has an opening that is as large as the pipe so it does not constrict the flow of the sediment.
For a great how to site on water heaters check out:
http://waterheaterrescue.com /
This is the best information I have ever found on water heaters.
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Roger Shoaf

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Danny,

I think sediment build up is the most common cause of water heater noise.
However, if you have "heat saver" nipples coming out of the top of your water heater, you may want to check or replace those too.
We installed a new electric water heater, with new "heat saver" pipe nipples. Anytime we used hot water we would get loud rumbling noises from the water heater. The more flow, the louder the noise. Running the bathtub faucets was the worst.
Anyway, I just installed a circulating pump on our system, and replaced the heat saver nipples with regular brass pipe nipples. The noise is gone!
I researched this a bit and it turns out that the little balls or flappers in the heat saver nipples can rattle or vibrate as water passes through them. It's amazing how much noise they can make.
Something to check...
Anthony
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Guys, I think that you have given me some ideas. I had wondered a bit as I was draining the tank about the outflow size of the drain, but figured "it must be right cause that's the manufacturer's own part". Now I can see that it's not maybe correct or even the best thing, even if they put it on.
I don't think I have heat saver nipples. I just checked. All that I can see coming out of the female couplings on the tank are what look like short, standard nipples. To this is screwed on a copper pipe adapter that has a female threaded opening (pipe threads) and hex flats on it. That, then attatches to the hot two copper pipe lines above with the usual methods of copper pipe and sweat on couplers.
Thanks,
Danny
HerHusband wrote:

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Danny,

You may not be able to tell from looking at the outside of the pipe. Mine just looked like short galvanized pipe nipples, except for little arrows stamped on the sides to show the directional flow. You couldn't see the little flappers inside until the supply lines were disconnected.
Anthony
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To this is screwed on a copper pipe adapter that has a

What you refer to as a copper pipe adapter is a dielectric union. This provides an electrical insulation between the copper and the galvanized pipe to prevent electrolysis.
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Roger Shoaf

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Roger,

I have plastic piping here, so I have no need for the dielectric unions.
However, I was doing some research on those unions and it sounds like they don't work well in real life. The theory is good, putting an insulator between dissimilar metals so they won't corrode from electrolysis. If the pipes were dry, it would work great. However, when the pipes are filled with water (a conductor) the corrosion apparently bridges the gap and the pipes corrode as if the union weren't there.
Just something I learned from plumbers who deal with this stuff every day...
Anthony
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If you don't think they work would you connect copper directly to galvanized pipe in your home? I sure wouldn't. Why don't you get that know-it all plumber to prove his theory with a volt meter.
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I found the information on www.plbg.com and a number of plumbers shared similar experiences. I don't claim it as fact, just relaying the information I read.
I'm sure the dielectric unions have to be better than a direct copper to galvanized connection, but it doesn't sound like they are the "perfect" solution.
The general recommendation was to use standard brass nipples to join the copper piping to the hot water tank. They apparently hold up fairly well, despite the copper content in the brass.
Anthony
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Greetings,
Is it possible that part of the anode rod has broken off and is bouncing around inside the tank? This might have happened when someone botched an attempt to replace the old anode rod, etc.
Hope this helps, William

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A piece of an anode rod bouncing around? I guess when they start making them out of plastic you might just have the answer there Willie ol buddie. Too Too funny. Bubba.
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'Any ideas on the various causes that could be at work, causing the rumbling?'
ME: Its a load of sediment stuck in the bottom of the tank . The heat from the burner has to go thru this sediment before it reaches the water in the tank. SO, you hear a popping or rumbling noise. As time goes on,..it will get worse . The bottom of the tank will run much hotter than normal too, which will speed up its eventual failure. What is most likely to happen is, the bottom seam of the tank will start to seperate and start leaking. On occasion , the entire bottom of the tank gives way and you have Niagra Falls -- just hope youre home if/when this occurs, and hope that your water shut off valves work ! (which most dont cause they havent been turned in 15 plus years). The efficiency and capacity of your rumbling tank , is less than it was when new. Id get rid of it very soon. No need to chance alot of mess to clean up. Water heaters are faily inexpensive when you consider they last for at least 12-15 years on average.
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