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hannahsugs's avatar

Why is my hot water heater making funny noises?

Asked by hannahsugs (3233 points ) September 24th, 2009

Recently, my hot water heater has started making gurgling/clanking noises whenever the burner is on. The heater is in the basement right below my bedroom, and we can hear it from bed.

Two things happened on the day it started making noises:
1) We turned the temperature up from “vacation mode” for the first time (we live in Tucson. when the normal “cold” tap water is over 90 degrees, you don’t really need a hot water heater).
2) We drained the sediment from the bottom of the tank, following the instructions. Apparently this is supposed to be done every 6 months, but we really doubt that whoever was living here before ever did it. We drained about 2 gallons of water from the tank.

I personally don’t think that the sediment has anything to do with it, although the noise does sound sort of like gurgling of air in the tank, as if it’s not all the way full. However, the tank should’ve refilled all the way, just as it would have if we’d turned on any tap in the house.

My boyfriend thinks the sound is sediment banging around, but I think that sediment is more like sand than big rocks, and how can sand make that much noise? And why would the water get agitated enough to throw sediment around?

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22 Answers

SpatzieLover's avatar

Sounds to me like sediment on the burner or element.

Have you taken out the element to see if it is encrusted? It’s a pretty cheap fix & a fairly easy DIY project.

DarkScribe's avatar

After you drained it, did you turn all of the hot taps in the house on briefly to ensure no air-locks? If you have one that has not been used yet, it could have air still in it and cause the pipes to “hammer”.

sandystrachan's avatar

I was going to say air in the system , or the pressure / temperature is set wrongly

SpatzieLover's avatar

Usually air hammer sounds like a jack hammer

DarkScribe's avatar

@SpatzieLover Usually air hammer sounds like a jack hammer

With air in the system it can make a loud clang or bang when another tap turns on or off – such as a washing machine operating. It doesn’t necessarily keep on “hammering”.

Harp's avatar

Sediment creates noise by trapping heat down next to the burner. Water isn’t supposed to boil in the water heater, and it usually doesn’t because as the water is heated by the burner at the bottom, it rises up the tank. But when sediment builds up, the heated water is held down by the layer of sediment instead of rising, and continues to heat until it boils. As the steam from the boiling breaks up through the sediment, it makes a gurgling sound.

cheebdragon's avatar

Calcium deposits most likely.

SpatzieLover's avatar

@DarkScribe I know. I’m a property manager. The sound she’s describing didn’t sound like a jack hammer to me.

DarkScribe's avatar

@SpatzieLover I know. I’m a property manager. The sound she’s describing didn’t sound like a jack hammer to me.

You are the only one who has used the term “jack hammer”. I have NEVER heard a hot water system sound like a jack hammer.

cheebdragon's avatar

My bedroom use to be right next to our hot water heater and they can get pretty fucking loud when there is enough calcium in there. (It would be compairable to putting a handfull of quarters in a washing machine and running it on heavy wash)

SpatzieLover's avatar

@DarkScribe I have many times. Air hammer can shake the pipes, whereas what @hannahsugs describes sounds like mineral build up

@cheebdragon I agree, LIME scale is loud!

DarkScribe's avatar

@SpatzieLover what @hannahsugs describes sounds like mineral build up

Perhaps you are right – perhaps not. Without being there all I can do is offer a suggestion – which I have done. A clanking noise sounds like air in the system to me – it sounds like something quite different to you. End of story.

hannahsugs's avatar

@DarkScribe: If it’s air in the system, would it be coming from the basement where the water heater is? I’m pretty sure it’s coming directly from the heater, not from the pipes in the walls.

hannahsugs's avatar

@SpatzieLover: It’s a gas heater, would that make a difference as far as cleaning the “element” ?

DarkScribe's avatar

@hannahsugs I’m pretty sure it’s coming directly from the heater, not from the pipes in the walls.

If it is definitely coming from the heater and not just echoing back from the heater when the pipe jumps, then it is unlikely to be an air lock. Pretty easy to tell, turn a tap on hard, then off again very rapidly. If the system clangs – it is likely an air lock.

squigish's avatar

I am also having a problem with the water heater under my bedroom, which I share with @hannahsugs I’m quite confident it’s not water hammer, for two reasons:

First of all, I’ve experienced water hammer before, at other houses, and this doesn’t sound anything like it. It’s not nearly loud enough, or abrupt enough. It’s more of a gurgling noise.

Second, the noise seems to happen when the burner is on, not necessarily when there’s an open tap. Of course, when a tap has been open for a while, that usually makes the burner come on, but not right away. If I crank up the temperature setting on the heater to force the burner to turn on, without opening any taps, it makes the noise. To me, it sounds exactly like boiling water, so I’m inclined to go with @Harp‘s explanation.

So, assuming that the problem is sediment, not air, what should we do about it? Is flushing the water heater by opening the bottom drain with the cold water supply switched on enough? Or should we drain it?

Also, we’re renting, so is this something we should just ask our landlord to deal with?

Harp's avatar

If it’s never been flushed before, your previous 2 gallon flush was probably not enough. It’s best done by hooking a garden hose to the drain so you can extract lots of water. Try turning the heater off well in advance of the draining so that all the crud can settle to the bottom. Close the cold water supply and open either the pressure relief valve at the top or a hot water tap in the house. Now open the drain valve.

There’s a chance that the drain will clog with sediment at some point. If it does, close the pressure relief valve or hot water tap (whichever you chose to open before starting the drainage) and turn the supply back on. This will build up some pressure and, hopefully, clear out the drain.

You may need to nearly empty the tank if it hasn’t been flushed before. Personally, I think this is the landlord’s responsibility. t not only creates the noise problem, but drastically reduces the efficiency of the heater, so it costs you money.

charliecompany34's avatar

at least you’re getting a warning. it’s about to go out or you need to drain it. one of the two.

SpatzieLover's avatar

@squigish Yes, the water heater is your landlord’s responsibility. Contact him/her tomorrow. Let the landlord know that you need it checked out and that you think sediment has built up on the burner or element.

@charliecompany34 is right…at least you are being forewarned by the heater that there is a problem. Often when there is a sediment build up, there will be little to no warning, then you’ll find a large flood when the heater springs a leak.

If you notice your water get very hot out of your taps before the unit gets repaired, that is your final warning before the element burns out.

paullewin's avatar

Actually NONE of these answers are correct! This one is: There is a plastic tube which extends down from from cold water entry into the hot water tank. This tube allows the cold water entering your tank to be directed to close to the bottom of the tank where it is heated. If the plastic tube did not exist, the cold water would not be completly heated. Anyway, what has happened to your tank is that the plastic tube has broken off up at the top of the tank. The broken plastic tube falls into the tank and as the tank heats water the tube moves around the tank and makes the sounds which you are hearing. Unfortunately, it is very difficult (if not impossible) to remove the broken plastic piece. If you remove the cold water entry pipe you can put your finger in the hole and if you do not feel a plastic pipe, yours has definately broken. You can purchase replacement plastic tube and you just drop it in the hole and reattach the cold water pipe. Be sure to remove the smaill broken piece which will still be in the opening. Unfortunately the broken large tube will continue to “clang” around in the tank until you replace the entire water heater…

squigish's avatar

Last night we flushed out the hot water heater. We turned off the burner for about 3 hours to let the sediment settle.

I was unable to turn off the cold water supply, because the handle of the valve was broken off, and it was totally calcified. I tried turning it with vise-grip pliers, and only managed to warp the valve.

So instead of draining the heater, which would have had to have been done with buckets, as the water heater’s in the basement and there’s no floor drain, we just ran a hose from the drain valve on the bottom of the heater to the kitchen sink, and ran it for about 45 minutes, which is about how long it took for the water to stop having a noticable amount of suspended sediment. I figure that we must have emptied the entire tank at least once, probably more than once.

The noise is still there. We took a lot of sediment out of the tank.

Also, I don’t really understand how sediment buildup could cause the water to be trapped next to the burner and boil. Could someone try to explain this?

It’s a gas water heater.

I made a recording of the noise, although the recording sounds more mechanical and metalic than the real thing. I’ll post again once I get it online.

The other thing we discovered is that there is no insulation whatsoever between the water heater in the basement and the bedroom floor, so even a relatively quiet noise will penetrate. Are gas water heaters supposed to make noise, aside from the hissing of the burner?

Thanks everyone for your help.

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