Tankless water heaters: casing leaks versus connection leaks

Internal leaks are definitely more of a headache in my book. Had one last year - turned out to be a cracked heat exchanger. Way pricier and more time-consuming than just tightening up a fitting or swapping out a valve at the connections. Connections are usually a quick fix, but when it’s inside the unit, you’re looking at parts and sometimes even replacement.

Drips from inside the box are a pain, no doubt, but I wouldn’t say leaks at the connections are always a walk in the park either. Sure, most of the time it’s just a matter of tightening things up or swapping out a gasket, but I’ve seen plenty of “simple” connection leaks turn into a mess - especially if they’ve been dripping for a while and you get corrosion or mineral buildup. Sometimes you open it up and realize the threads are shot or the fitting’s cracked from someone over-tightening it last time. Then you’re chasing parts or even re-piping sections.

But yeah, internal leaks - especially something like a cracked heat exchanger - are usually worse for your wallet and your schedule. Once you’re inside the unit, you’re dealing with more teardown, more specialized parts, and sometimes you’re at the mercy of the manufacturer’s lead times. Plus, if it’s an older unit, good luck finding parts that fit without some Frankenstein-level modifications.

I guess for me, it comes down to how early you catch it. A slow drip at a connection that goes unnoticed can rot out a cabinet or rust up a bunch of stuff before anyone realizes. But if you spot it early, it’s usually a quick fix. Internal leaks, on the other hand, almost always mean something’s failed in a big way.

Had a job last winter where what looked like a tiny drip at the bottom turned out to be a pinhole in the coil. Ended up replacing the whole coil assembly because patching wasn’t gonna cut it. Customer wasn’t thrilled about the bill, but there wasn’t much choice.

Guess my take is: neither one’s great, but internal leaks tend to hit harder - unless you get unlucky with a connection leak that’s been ignored for months. Either way, regular checks save headaches down the line... but I know how easy it is to put that off until there’s water on the floor.

- You nailed it - catching things early is everything.
- I’ve definitely seen “just a drip” at a fitting turn into a full-on cabinet replacement after months of neglect.
- Internal leaks, though... yeah, those are wallet-busters. Once you’re opening up the box, it’s rarely a quick fix.
- Still, I’d rather deal with a connection leak any day if I spot it fast. Less mess, less downtime (usually).
- Regular checks sound boring but they really do save you from those ugly surprises. Easier said than done, though - I’m guilty of ignoring that little puddle until it’s too late more than once.

- Internal leaks, though...

I’ve seen both types of leaks, and honestly, I’d take a connection leak over an internal one every single time. If it’s just a bit of water at a fitting, you can usually shut things down, dry it off, and tighten or replace the joint - done in an hour or two if you’re lucky. Worst case, maybe a new section of pipe or a valve.

But when the drip is coming from inside the unit? That’s where things get ugly. You’re dealing with electronics, sensors, heat exchangers - stuff that’s not meant to get wet. Even a small internal leak can fry a board or corrode parts you can’t see without tearing the whole thing apart. Plus, manufacturers aren’t always generous with replacement parts, and labor adds up fast.

Neglect is the real killer, though. I’ve lost count of how many times someone ignored a “harmless” drip until it turned into mold or rot behind the wall. Quick checks now and then really do save headaches later, even if it feels like overkill.

Even a small internal leak can fry a board or corrode parts you can’t see without tearing the whole thing apart.

Couldn’t agree more - internal leaks are like the silent assassins of equipment. I’ve seen a tiny drip take out a whole control panel before anyone even noticed. At least with a connection leak, you usually get a fighting chance.

Yeah, those sneaky internal leaks are the worst. I once spent hours chasing a weird electrical issue, only to find a tiny water trail inside the panel - by then, half the board was toast. At least with a connection leak, you usually spot the drip or puddle before it gets out of hand. Still, both can be a pain... just gotta stay vigilant and check those hidden spots every now and then.

- Gotta say, I actually worry more about connection leaks.
- They can spray or drip right onto drywall or flooring, and if you miss it for a day or two, you’re looking at mold or warped boards.
- Internal leaks are a pain to find, but at least the damage is mostly contained inside the box... usually.
- Maybe I’m just paranoid after dealing with a slow drip behind my washing machine that trashed the baseboard before I even noticed.

Drips at the connections are my personal nemesis. Had one sneak up on me under a kitchen sink - by the time I caught it, the cabinet bottom looked like a potato chip. At least with a box leak, you usually get a puddle right there and it’s obvious. Connections, though... they’re like ninjas. And yeah, drywall + water = instant regret. I keep a stash of those moisture alarms now, just in case.

Honestly, I think connection leaks are way more dangerous than box leaks. At least with a box, you get a clear sign - big puddle, obvious mess. Connections, though? They can drip for weeks before you notice anything’s wrong, and by then you’re dealing with warped wood or even mold. Ever had one of those slow leaks that only shows up when someone runs the dishwasher or does laundry? Those are brutal. Do you guys check your connections regularly, or just rely on alarms?

I hear you on those sneaky connection leaks. Had a “fun” surprise under my kitchen sink last year - tiny drip from the hot water line, probably going for weeks. Only found it because the cat started hanging out under there (guess she liked the sauna vibes). By then, the bottom of the cabinet was all swollen and gross. I try to check connections every few months now, but honestly, life gets in the way and sometimes it’s just luck when I catch something.

I’ve looked at those smart leak detectors, but haven’t pulled the trigger yet... are they actually reliable? Or do they just go off every time someone spills a little water? Also, anyone else get paranoid after fixing one leak and start checking every single pipe in the house for weeks?

Had a similar thing with a slow drip behind my washing machine - didn’t notice until the wall started to bubble. As for those leak detectors, I’ve installed a couple. They’re not perfect, but honestly, they’ve saved me twice now. Only false alarm was when my kid knocked one over with a mop. I’d rather deal with a few beeps than another cabinet rebuild...

Drips from the box or leaks at the connections… honestly, both sound like a nightmare, but I think the connection leaks are sneakier. When I moved in, I thought a little puddle under the sink was just from washing dishes too enthusiastically. Nope - turned out the connection was loose and slowly soaking into the cabinet. Took me way too long to figure it out. Is it just me, or do these things always happen right after you finally organize under there? Those leak detectors sound handy, though. Do they actually pick up on slow drips, or only bigger leaks?

Is it just me, or do these things always happen right after you finally organize under there?

Seriously, it's like the universe waits until I've lined up all my cleaning supplies before deciding to spring a leak. And yeah, I totally agree - connection leaks are way sneakier than box drips. At least if the box is dripping, you usually spot it right away. But those slow leaks? They just lurk and turn your nice cabinet into a warped mess before you even know what's up.

About the leak detectors, I've wondered the same thing. Some of them claim to pick up even a tiny bit of moisture, but I kinda doubt they catch every single drip. Has anyone actually put one to the test with a super slow leak? I’m picturing a drop every few minutes - does that even register, or does it need a little puddle to set it off? Also, are they worth the hassle, or do they just end up beeping every time you splash a bit of water around?

Yeah, those slow leaks are the worst. I’ve had one under my kitchen sink that warped the whole bottom panel before I even noticed. As for leak detectors, I’ve tried a couple of the cheap ones - they do pick up small puddles, but honestly, a single drop every few minutes might not set them off right away. They’re not perfect, but they’re better than nothing, especially if you’re not checking under there all the time. Worth it for peace of mind, in my opinion, but they can be a little sensitive to splashes.

Honestly, I’ve seen more damage from slow drips at the connections than from the box itself. The thing is, a drip at a fitting can run down pipes and soak into places you’d never think to check - sometimes it’ll even end up behind walls or under floors before you spot it. Those cheap leak detectors are hit or miss, like you said. Ever tried putting a paper towel under the pipes for a few days? Not high-tech, but it’s caught a couple sneaky leaks for me when the sensors missed them. Curious if anyone’s had better luck with the pricier detectors or if it’s just marketing hype...

I get what you’re saying about the paper towel trick - it’s simple and sometimes effective. But honestly, I’ve had the most luck just doing a thorough visual inspection with a flashlight, especially around the shutoff box. Some of those pricier leak detectors do have better sensitivity (like the ones with WiFi alerts), but I’ve seen them false alarm from condensation or even a humid day. Not sure they’re worth it unless you’re away from home a lot. Sometimes old-fashioned vigilance beats gadgets...

Honestly, I’m with you - sometimes the best “tech” is just your own eyeballs and a decent flashlight. I bought one of those smart leak sensors thinking I’d be ahead of the game, but it went off during a steamy shower and nearly gave me a heart attack. The paper towel trick is great if you’re paranoid like me, but nothing beats crawling around and checking for drips yourself. Plus, it’s free... unless you count the chiropractor bills.

I hear you on the “tech” overload. I tried one of those fancy moisture alarms under my kitchen sink, and it chirped every time I ran the dishwasher - turns out it was just condensation, not a leak. Honestly, I trust my knees and a flashlight more than any gadget at this point. The only downside is finding all the dust bunnies while you’re down there... but hey, two birds with one stone, right?

I totally get where you’re coming from about trusting your own eyes (and knees) over gadgets. I tried one of those leak sensors in my laundry room once - thing was so sensitive it went off every time we had a humid day. My dog started barking at it, which didn’t help my nerves much.

Still, I’m a little paranoid after dealing with a slow leak at the shutoff valve under our bathroom sink last year. It was just a tiny drip, but over time it warped the cabinet floor and left a nice little mold patch behind the basket of cleaning supplies. Didn’t even notice until I was down there swapping out the trash bags. Since then, I’ve been doing the flashlight squat more often than I’d like to admit.

Honestly, I’d rather have a dust bunny army than black mold any day. Those slow drips at the connections are sneaky - at least if it’s coming from the box or the trap, it’s usually pretty obvious and you can catch it before it does too much damage. Connections, though... they’ll betray you quietly.

I still keep a cheap sensor tucked back there, but I don’t rely on it. It’s more of a backup, like a smoke alarm for leaks. Nothing beats getting your hands dirty and having a look yourself every once in a while. Just wish my knees would stop complaining about it...