Unable to identify sound made by hot water heater after heating stops
There's a bit of a story to get to where I am that may or may not help answer the question, so sorry in advance for the lengthy post. I just wanted to be detailed.
To start with, I had my local plumber come out for yearly maintenance about a month ago. The bulk of the visit was draining the hot water heater. It wasn't my first time having this done at this house, but one thing I was concerned with was the color of the water coming out. It was very rusty-looking. Almost red clay muddy. In fact, the plumber that came out wanted to try getting into the water bits by the street to see if there was a possibility that dirt was getting in (he couldn't because it was locked, but he also said if there was I'd be seeing it in the water in the house anyway). He noted that he'd never seen it that bad. Whatever it was has left a bit of a stain on the driveway as he drained it toward the street. It took about two hours from the time he left before I could start getting clear water out of the faucets in the house (enough time for the tank to refill and heat the water then stop) when calling for hot water.
One thing to note is that the plumber had mentioned something about the anode rod off-hand. It was the first time I'd heard of it and it certainly hasn't been replaced. The water heater is about 7.5 years old, but I'm the only one who has ever used it. It serves a whole house, but there's only enough water usage for one person, generally only using hot water for showers. I don't know what state it's in currently, but one of my concerns following that visit was that it might be completely eaten up and the tank might be rusting out from the inside. Not sure. If anyone thinks that might be related to the water that was coming out, let me know. But other than the color of the water, there weren't any problems noted with the water heater during the visit.
Anyway, fast forward to this week, I believe Sunday night. I accidentally ran some hot water out of the kitchen sink when I didn't get it all the way to cold. It was basically lukewarm. Not the first time, obviously. But about 10-15 minutes later, enough time for the water heater to get some more water in and get the temperature back up, I heard this loud metallic pop/bang. The best ways I can describe it are like if you were to bend a sheet of metal and pop it back into place, or if you took an empty drink can and crushed the side a little, then popped it back out (or maybe gave it a good flick). So I went about trying to troubleshoot. I went outside and looked and nothing looked off. I ran the hot water in the kitchen sink for about 4-5 minutes and then went out to the garage to monitor while it filled and heated. At the time the heating process ended, I heard it again, so I know it came from the hot water heater, but I don't know exactly what part is making the noise. After coming back in, it did it again a few minutes later (no additional hot water had been run). Then it did it again some 30 minutes or so later. After another hour or so, I didn't hear it anymore, so I went upstairs to take a shower and came back down to monitor, but nothing happened for the rest of the night/week.
Flash forward to today, several days later on Friday when I always run the dishwasher, and about 10-15 minutes after the dishwasher cycle ended, it did it again. I went out to check and didn't see anything wrong with it. Less than a minute after coming back in, I heard it again. About 40 minutes after that, it did it again, and then again maybe 30-40 minutes after. That was maybe 45-60 minutes ago, but I haven't heard it again (yet).
I called the plumber and it's already after hours for them. They told me they wouldn't be able to make it out this weekend due to after-hour call volume, but assured me it would be fine to just let it ride over the weekend until everyone on staff is back in on Monday. According to them, the only reasons for concern would be if I had noticed the tank swelling or saw any water leaking (I haven't). They confirmed that I had an expansion tank attached (I do) and said that as long as that's there, I shouldn't need to worry until someone can get out and look.
So the tl;dr is basically that the water heater in the garage is making a metallic sound like a metal pop or clang or something that is loud enough to hear inside the house after the water heats up after use, but seemingly only when hot water is used in the kitchen sink or adjacent dishwasher and not from the upstairs shower.
The nature of the sound leads me to believe it may be something banging on the outside of the unit rather than on the inside where it's full of water, maybe a pressure valve snapping or something? I don't know. I've googled this more times this week than I can count and nothing that comes up as a sound a water heater might make matches what I'm hearing. I can't identify any visual problems with the water heater itself, front, sides, top, back, etc. If anyone has any guesses, please let me know. I'm trying to arm myself with whatever knowledge I can for when someone comes out here to look, even just a suggestion on some things it could be just so they have some idea on where to start looking.
Thank you in advance for anyone able to help, and I can try to provide more information if necessary, but I don't know that there's much to add beyond what's already here.
Posted Nov 13, 2021, 1:23 AM UTC
It sounds like from your description the expansion tank has failed and when the water heater completes it heat cycle the tank is having a excessive amount of thermal expansion causing the internal shell to possibly bulge and pop in a sense.
On a side not what is your houses water pressure? That can cause a lot of issues coupled with what sounds like thermal expansion inside the water heaters tank.
As for the brown looking water you may have a large amount of iron in your water and it’s building up in the bottom of your water heaters tank as settlement. I see a ton of calcium build up in the tanks from where I’m from due to the city’s water is just so chocked full of it. Little white chunks of settlement every time we drain a tank.
Unfortunately I'm not sure about the water pressure. I don't have a gauge to check with either. I can't say that it seems like there's a particular problem with it, though, just from observing. I know that doesn't mean much.
I'll continue monitoring, but if you think the expansion tank is failing, do you think I'm in any immediate danger? The on-call plumber I talked to said it should be fine through the weekend as long as the tank was there, but I'm guessing he didn't account for it possibly failing. I can say for sure that the T&P valve isn't leaking or corroded, but I didn't check the tank for temperature. I'll try to do that shortly, but I don't know what else to check.
Regarding the water, some quick Googling for pictures indicates it may be just that, though most of the results coming back seem to mention well water, which I don't have, so I wonder.
Well water does have a lot more of a issue with iron build up. Although you could have galvanized pipes somewhere in the plumbing which will corrode and build up the red iron look in the tank as well. There’s a ton of possibilities for the water discoloration.
You’ll be safe as long as the t&p valve isn’t corroded shut so no rushing into a weekend service or on call. That can get highly expensive.
As for the water pressure, I would like to suggest to run by Home Depot, Lowe’s, or ace hardware and purchase a pressure gauge. It’ll have a 3/4” hose bib female threaded end on it and you’ll attach it to a hydrant and turn it on. I like to use the ones with a small bleeder valve to test the pressure at peak and the pressure at a opened down point. If it’s anything over 65 psi then you’ll need a new pressure regulator most likely. That’ll also safe the fixtures in your home from unnecessary wear and tear as well. If it’s under 65 psi then your pressure is fine.
I’d run some hot water, 5 minutes. Wait for the reheat to finish while standing at the tank. And then I’d bear hug the tank and place a ear to the side and hear what it’s doing after the reheat and go from there to ensure it may actually be the tank in fact. I have seen multiple tanks explode from the back and only being 7 years or so old on a seem so don’t get near that part when checking. It’s normally on the back of the outer shell so no worries most of the time. But when they did pop the homeowners would always say they heard a weird metal popping noise and then whoosh came the water filling up the drain pain so fast it flooded the floor etc.
Thinking back regarding the pressure in the house, I did recall a brief period some 3-4 months ago where I sporadically had cloudy water (from bubbles), even when it was cold, but it ended up going away before I ever called anyone out to look and it wasn't even consistent across a day. It was usually at night for just a few nights. Don't know if that could have caused some long-term damage or not, but I can say with certainty that it hasn't done that since, so the timing seems off for this particular problem.
Some quick checks on the expansion tank seem to paint it being okay, but I'll make sure they look at it. I'm kind of having some trouble telling how it sounds. Seems to depend on how hard I tap it with my knuckle, but I can certainly hear it get a bit of a metallic ring on the side with the right tap. I think the bigger issue is that it's on top of the water heater, so I'm having some trouble reaching it on the back side without a ladder. All I've got is a chair. It doesn't feel warm throughout, but it also doesn't really feel warm anywhere. No leaks or condensation that I can find, though.
As far as checking the pressure, I'll make sure it gets checked, but it's already well past 10 PM here so no dice going basically anywhere to get anything right now.
I got ya, the bubbles could be from services being performed on the main service lines from the utility company and air entering the lines. That’s what I’ve come across mostly.
After the pressure check and everything else is checked out please let me know what the turn out comes down too. I’m genuinely curious and would love to hear about the fix.
Oh and expansion tanks are around $25 to $75 dollars depending on the brand you decide to use. I’d just go ahead and replace the expansion tank as a precaution and as part of the process of elimination. It’s as easy as shutting off the water, unscrewing the old tank, putting some pipe thread sealant on the new tank, and tightening it in. Well cheaper then a plumber doing it as well if you decide to do it yourself.