Tankless water heaters: casing leaks versus connection leaks

Honestly, I’d take a slow drip over a hidden leak any day, even if it means getting a face full of dust bunnies under the sink. At least with a visible drip, you’ve got a shot at catching it before it turns into a full-blown disaster. Hidden leaks, though... those are sneaky. By the time you spot the water stain or that musty smell, you’re already looking at drywall repair and maybe even some mold remediation if you’re unlucky.

One thing I always tell folks - don’t ignore those tiny puddles or damp spots around connections. Sometimes it’s just condensation, but sometimes it’s the start of something bigger. I’ve seen folks shrug off a little moisture, only to end up with warped cabinets and ruined flooring down the line. Not fun.

If you’re crawling under there anyway, might as well check all the fittings and give everything a gentle tug. Just don’t overtighten - learned that one the hard way when I cracked an old valve. It’s always a balance between being thorough and not making things worse...

If you’re crawling under there anyway, might as well check all the fittings and give everything a gentle tug. Just don’t overtighten - learned that one the hard way when I cracked an old valve.

That’s a good tip about not overtightening. I actually did that with a compression fitting on my first week in this house - thought I was being “thorough” but ended up with a tiny spray instead of a drip. Still not sure how tight is "tight enough" though... Is there some trick to knowing when to stop, or is it just trial and error?

Still not sure how tight is "tight enough" though... Is there some trick to knowing when to stop, or is it just trial and error?

Honestly, it’s less trial and error than people think. With compression fittings, you want it snug, then maybe a quarter turn more - don’t muscle it. If you’re using two wrenches and really cranking, that’s too much. I’ve seen more leaks from overtightening than under. Hand tight, then a little extra, and check for drips after turning the water back on. If it’s still leaking, THEN give it another nudge.

Leaks from overtightening can be a pain, but I wouldn’t downplay the risk of under-tightening either. I’ve seen plenty of slow drips that looked harmless at first, but ended up causing way more damage over time than a connection that was a bit too snug. That “hand tight plus a quarter turn” guideline works most of the time, but honestly, every fitting feels a little different. Sometimes you just have to trust your gut and keep an eye on it for a day or two... water has a way of finding the smallest gaps.

I get what you’re saying about under-tightening - had a job last month where a tiny drip from a compression fitting went unnoticed behind a vanity for weeks. By the time we found it, the cabinet base was basically mush. Thing is, overtightening can be just as sneaky. I’ve seen brass nuts split clean in half from too much muscle, and then you’re dealing with a full-on spray instead of a drip. Honestly, I wish there was a foolproof way to know when it’s “just right,” but it really does come down to feel and experience. Water always wins if you give it enough time...

Honestly, I wish there was a foolproof way to know when it’s “just right,” but it really does come down to feel and experience. Water always wins if you give it enough time...

That’s the part that gets me every time - water’s patient, and it’ll find any weakness you leave behind. I’ve been told “hand tight plus a quarter turn” for compression fittings, but honestly, sometimes that’s too much, sometimes not enough. Had a shutoff valve where I followed that rule and still ended up with a hairline crack in the nut. Didn’t notice until the homeowner called about water pooling under the sink a week later.

I’d almost rather deal with a box drip than a slow leak at a connection. At least with a box drip, you usually spot it right away when you open things up. Those sneaky connection leaks can rot out cabinets or floors before anyone knows what’s happening. Still, I get why people overtighten - they just want to be sure it won’t leak. But yeah, there’s no substitute for getting a feel for it over time. Sometimes I wish fittings came with torque specs like car parts... but then again, half the time you can’t even get a wrench in there straight.

Sometimes I wish fittings came with torque specs like car parts... but then again, half the time you can’t even get a wrench in there straight.

Man, that hits home. I remember crawling under a kitchen sink at 2am - water everywhere, homeowner in a panic. Turned out to be a tiny leak at a compression fitting behind the garbage disposal. The kicker? I’d installed it myself a month earlier, thought I’d nailed it. Did the “hand tight plus a quarter turn” thing, but I guess the threads were a little off or maybe the ferrule wasn’t seated just right. By the time I found it, the cabinet bottom was already starting to swell.

Honestly, I’d take a box drip any day. At least you get a puddle on the floor and you know something’s up. Those slow leaks are like termites - silent, but they’ll wreck your day (and your cabinets) if you’re not careful. I’ve learned to run a dry paper towel around every joint before I pack up, just in case. Not foolproof, but it’s saved me a few callbacks. Water’s sneaky, no doubt about it.

I get where you're coming from about slow leaks being the worst, but honestly, box drips freak me out more. Here’s why:

- Big puddles can mean a lot of water in a short time - if you’re not home, that’s a disaster fast.
- Slow leaks are sneaky, but at least the damage is gradual. You usually catch it before it’s catastrophic.
- I always put a water alarm in the cabinet just in case. Cheap insurance.

Maybe I’m just paranoid, but I’d rather deal with a hidden trickle than a full-on flood... especially with wood floors nearby.

Drips from the box are like that horror movie jump scare - one minute, everything’s fine, next minute you’re wading through your kitchen. I get what you mean about the “big puddles” being a nightmare, especially if you’re out for the day and come back to your own personal indoor pool. That’s a fast track to warped wood floors and a lot of explaining to the landlord (ask me how I know...).

But I gotta say, slow leaks still keep me up at night. They’re like the silent ninjas of water damage. You don’t see them, you don’t hear them, and then suddenly you’ve got mold colonies setting up shop behind your cabinets. At least with a box drip, you get a dramatic warning - like, “Hey! Something’s wrong here!” With slow leaks, it’s more like, “Surprise! Your cabinet’s rotted and your insurance deductible just doubled.”

I always put a water alarm in the cabinet just in case. Cheap insurance.

That’s smart. Those little alarms are lifesavers. I’ve started putting them everywhere after one too many “mystery puddle” incidents. Once had a slow leak under the bathroom sink that went undetected for weeks. The only reason I found it was because my cat kept sniffing around the cabinet. Turns out, he was onto something... and I was onto a soggy mess.

But yeah, if I had to pick my poison, I’d probably rather deal with a box drip too - at least you know what you’re up against. Slow leaks just feel sneakier, like they’re plotting against you. Either way, water always finds a way to ruin your day, right?

Honestly, I’ve seen more long-term headaches from those sneaky connection leaks than the dramatic box drips. Had a client once who thought their dishwasher was just “sweating” a bit - turns out, the slow leak had been soaking the subfloor for months. By the time we opened it up, it was like peeling back layers of a rotten onion. At least with a box drip, you get that immediate “fix me now” moment. Those hidden leaks just quietly destroy everything in their path...

By the time we opened it up, it was like peeling back layers of a rotten onion. At least with a box drip, you get that immediate “fix me now” moment.

That’s such a good point about the “quietly destroy everything in their path” part. I’ve always wondered - how do you even spot those sneaky leaks before it’s too late? I mean, a box drip is obvious, but with connection leaks, are there any subtle signs besides the classic musty smell? Or is it just luck if you catch it early?

I had a similar thing happen under my sink. I thought the condensation was from running cold water, but nope - tiny leak, slow rot. It made me rethink how often I check for moisture or weird discoloration around appliances. Does anyone use those water alarms? Are they actually reliable, or do they just give false alarms all the time?

It’s wild how the stuff you can’t see ends up being so much worse for the environment too. All that wasted water and ruined wood... Makes me think regular checks should be as routine as changing air filters.

Honestly, I’d take a dramatic box drip over a sneaky connection leak any day. At least with a box drip, you get that “oh crap, better fix this now” moment. Those slow leaks are like the ninjas of home damage - silent, deadly, and they always seem to strike when you’re least expecting it. I found one behind my washing machine last month. Thought the cat had knocked over her water bowl again, but nope... just a tiny, evil leak that had been quietly soaking into the drywall for who knows how long.

I tried one of those water alarms under the sink after that. It actually worked - went off at 2am and scared me half to death. But hey, better a false alarm than a rotten cabinet, right? I do wish there was a less jump-scare-y way to catch these things early. Maybe we need “leak check” to-do lists next to our “replace air filter” reminders. Or maybe I just need to stop pretending I’m handy and call a plumber more often...

I hear you on the ninja leaks. Those things are the worst - by the time you notice, it’s like, “Why does my baseboard feel like a wet sponge?” I’ll take a dramatic box drip too, just for the sheer obviousness of it. At least you know where to aim the bucket. Water alarms are great, but man, they really do have a way of making you question your life choices at 2am. I keep meaning to add “check under sinks” to my monthly routine... but then I get distracted by literally anything else.

I get the appeal of the obvious box drip - at least you know where the water’s coming from. But are we underestimating how much damage those can do if you’re not home for a few hours? I’ve seen a box drip turn a laundry room into a swamp in less time than you’d think. Ninja leaks are sneaky, sure, but sometimes those dramatic ones are just as bad, just... faster. Do water alarms really help that much, though? I keep wondering if I’d just sleep through it anyway.

Honestly, I’m more worried about those slow leaks at the connections. The box drips are dramatic, yeah, but at least you notice them right away - unless you’re on vacation or something. The sneaky ones can rot out your floor before you even realize there’s a problem. As for water alarms, I’ve got one and it’s loud enough to wake the dead, but I still wonder if I’d hear it with the bedroom door closed. Maybe peace of mind is worth it, though...

The sneaky ones can rot out your floor before you even realize there’s a problem.

Yeah, those slow leaks are the real troublemakers. I’ve seen folks pull up their vinyl and find black mold or warped subfloor from a tiny drip that went on for months. The box drips are messy but at least you know right away, like you said. Water alarms help, but I get what you mean - if you’re a heavy sleeper or the door’s closed, who knows? I wish there was a foolproof way to catch those connection leaks before they do damage, but it always seems like you find them after the fact...

- Had a similar scare last month - noticed a weird soft spot by the dishwasher and, sure enough, slow leak at the hose connection.
- Took ages to notice since it was under the cabinet and totally silent.
- Ended up replacing a chunk of subfloor... not fun or cheap.
- Kinda wish I’d checked under there sooner, but who actually does that unless there’s a puddle?
- I’ve started keeping a cheap moisture sensor near the connections now. Not perfect, but better than nothing.

Drips from the box are annoying, but honestly, those slow leaks at the connections are way sneakier and more destructive in my experience. Had a client who thought their dishwasher was fine - until their kitchen tiles started buckling. Turned out the hose clamp was just loose enough to let water seep out over months. By the time they caught it, the cabinet base and half the subfloor were toast. I always tell folks: check those connections at least twice a year, even if it feels paranoid. Moisture sensors help, but nothing beats a quick look now and then.

Honestly, those sneaky connection leaks are the worst. Drips from the box at least announce themselves, but a slow leak under the sink? That’s like water damage on stealth mode. I always tell people - hand-tighten, then give it a quarter turn with a wrench. And yeah, moisture sensors are great, but nothing beats sticking your head under there and feeling around for dampness every few months. Learned that the hard way after a fridge line took out my baseboards...

I hear you on the stealth leaks - those are the ones that keep me up at night. I’ve had tenants call about a “musty smell” only to find out a tiny drip under the bathroom vanity’s been soaking into the subfloor for who knows how long. By the time you spot it, you’re looking at warped cabinets and maybe even mold remediation. Drips from the box are annoying, sure, but at least they’re visible and usually get reported fast.

I’m curious - do you trust those braided supply lines with built-in shutoffs? I’ve swapped out a bunch of old plastic lines for them, but I still get nervous about connections behind appliances where nobody ever checks. Seems like no matter how careful you are, there’s always some spot that gets overlooked. How do folks here balance between proactive checks and just hoping for the best?