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Re:Hitachi launches CO2 heat pump water heaters with solar-f... by numpad0 on Thursday September 10, 2026 @10:12AM (#49644032)
> How long do you sit in a bath?

80kg of meat can hold a lot of heat. It cools quicker than you think it would. Also, Japanese families often share the bathwater within themselves(but everyone showers outside the tub first), and the water will become lukewarm at some point in that use case.

> My immediate reaction to this is, “there’s a way for my house to be remotely flooded”.

Yep, remotely operating a machinery will always have some risks. Every machinery should have someone with an emergency stop button should be monitoring it at all time, ideally. But it's a well engineered tub auto-fill in the shower room, it effectively belongs to "inherently safe" category of equipment.

Re:Hitachi launches CO2 heat pump water heaters with solar-f... by germinalphrase on Thursday September 10, 2026 @10:31AM (#49644376)
Do you have a water drain in your bathroom floor?

This is uncommon in the US, so a bath overflow quickly becomes a significant structural issue.

Re:Hitachi launches CO2 heat pump water heaters with solar-f... by pbhjpbhj on Thursday September 10, 2026 @11:50AM (#49645811)
But USA bath tubs have overflows (redirecting water into the drain if the taps are left on), surely?
Re:Hitachi launches CO2 heat pump water heaters with solar-f... by compiler-guy on Thursday September 10, 2026 @12:00PM (#49645952)
In the US, any tub made past about 1900 or so has an overflow drain that prevents overfilling. The adoption of such drains not quite contemporaneous with the adoption of indoor plumbing, but very soon after.

It's the metal plate usually just below the faucet that looks like it might be useless. But it has an opening underneath to let the overflow water in. These are always sized to handle more water than the faucet can output.

This is basically a non-concern in anything but very, very old, unremodeled bathrooms.

The sinks do as well, but it is more obvious.

Re:Hitachi launches CO2 heat pump water heaters with solar-f... by sgerenser on Thursday September 10, 2026 @12:47PM (#49646705)
Im not sure about bathtubs, but in the U.S. it's apparently legal to sell lavatory sinks without an overflow. Ask me how I know.
Re:Hitachi launches CO2 heat pump water heaters with solar-f... by compiler-guy on Thursday September 10, 2026 @02:00PM (#49647840)
This puzzled me and I looked it up, and yes, sinks without overflow meet code [1] (but not tubs). So your situation was apparently legal.

But the sibling comment to this one, where a sink had an overflow, but it was not connected, did not meet code [also 1].

Go figure. There must be some reasoning there, but I'm confused as to what it is.

https://forms.iapmo.org/email_marketing/codespotlight/2018/m...

Re:Hitachi launches CO2 heat pump water heaters with solar-f... by saalweachter on Thursday September 10, 2026 @08:17PM (#49651885)
Code sometimes makes allowances for situations which aren't ideal, as long as they aren't deceptive or creating a false sense of security.

So if you have old two-prong outlets in your house from back when, those are allowed.

If you replace them with a three-pronged outlet which is ungrounded, that breaks code.

If the three-pronged outlet is a GFCI outlet labeled with NO ELECTRICAL GROUND, that is allowed.

Re:Hitachi launches CO2 heat pump water heaters with solar-f... by craftkiller on Thursday September 10, 2026 @01:20PM (#49647241)
My last apartment had the overflow drain hole but it wasn't attached to anything. The water just went directly into the wooden cabinet underneath. Madness. Literally worse than not having the hole because it reduced the capacity of the sink. This is what happens when landlords who DGAF hire handymen who DGAF to do all the work on their units.
Re:Hitachi launches CO2 heat pump water heaters with solar-f... by AngryData on Thursday September 10, 2026 @04:41PM (#49649893)
To be fair to the potential handyman or contractor many overflow drains are integrated into the sink drain before they attach anything. It might have been the landlord buying temu style sinks with fake overflow holes.
Re:Hitachi launches CO2 heat pump water heaters with solar-f... by seanmcdirmid on Friday September 11, 2026 @03:23AM (#49654709)
Many overflow drains are not or are poorly connected. If you buy a new home, the inspector will usually skip to overflow test because it will likely fail.
Re:Hitachi launches CO2 heat pump water heaters with solar-f... by eru on Monday September 14, 2026 @01:22AM (#49692320)
Well, it's also legal to sell food that tastes bad. Doesn't mean you should buy it.
Re:Hitachi launches CO2 heat pump water heaters with solar-f... by numpad0 on Thursday September 10, 2026 @11:45AM (#49645720)
The tub sits in a big shower booth. Other bathroom amenities like sink and washing machines are installed outside the booth. Toilet is usually a separate room entirely. So no problem overflowing water onto the floor since that's how you take a shower.
Re:Hitachi launches CO2 heat pump water heaters with solar-f... by SoftTalker on Thursday September 10, 2026 @11:34AM (#49645523)
Bathroom floor drain is common (might even be a code requirement?) in commercial buildings but not in homes.
Re:Hitachi launches CO2 heat pump water heaters with solar-f... by PotatoPrime on Thursday September 10, 2026 @12:42PM (#49646639)
All my tubs and sinks in the bathrooms have an 'overflow drain' near the top which you are unable to fill beyond. Is there any reason why that wouldn't be sufficient?
Re:Hitachi launches CO2 heat pump water heaters with solar-f... by atrus on Thursday September 10, 2026 @01:28PM (#49647386)
Yeah, if the drain in the sink is clogged. US bathroom pipe is 1.25" which will (probably) lead to a 2" and 4" pipe eventually (depending on when, where, and how your house was built ofc). The hole in the sink leads to the same initial pipe.
Re:Hitachi launches CO2 heat pump water heaters with solar-f... by AngryData on Thursday September 10, 2026 @04:38PM (#49649851)
It makes the tub taller than it is deep by a little bit and doesn't look as nice are the only reason I can think of. A little bit of splashed water just isn't a big deal in most wet bathroom setups. They could also just put a drain right off the side of the tub.
Re:Hitachi launches CO2 heat pump water heaters with solar-f... by eru on Monday September 14, 2026 @01:21AM (#49692312)
My Japanese style bathroom here both has an overflow in the tub and a drain in the middle of the room.
Re:Hitachi launches CO2 heat pump water heaters with solar-f... by danparsonson on Thursday September 10, 2026 @12:53PM (#49646804)
In Japan it's very common for bathrooms to be wet rooms; likewise South Korea and Taiwan among others.
Re:Hitachi launches CO2 heat pump water heaters with solar-f... by KPGv2 on Friday September 11, 2026 @12:42AM (#49653644)
To add to this, it's so nice. Sit on a stool in the middle of the room and rinse, soap up, scrub to exfoliate, rinse, then roll the lid of the bath open and soak in a sub much deeper than an American one. Bath is programmable to maintain a constant temperature.

Basically a spa experience every day.

Re:Hitachi launches CO2 heat pump water heaters with solar-f... by bschwindHN on Friday September 11, 2026 @03:18AM (#49654662)
I wish more people knew how nice it is! And the toilet is in a completely separate room so there's no contention among one person who wants to take a bath and another who needs to use the toilet.

I just wish dish washers and dryers were more common in Japanese households. I'm in Okinawa where dryers are a lot more "standard", but dish washers are relatively rare.

Re:Hitachi launches CO2 heat pump water heaters with solar-f... by greggsy on Thursday September 10, 2026 @03:15PM (#49648906)
I believe it’s mandatory in Australia
Re:Hitachi launches CO2 heat pump water heaters with solar-f... by prawn on Thursday September 10, 2026 @11:05PM (#49653088)
Yes, I can't remember seeing a bathroom or laundry here that didn't have a floor drain. Seems insane for that to not be standardised. I briefly lived with a bathroom in the UK that was carpeted?!
Re:Hitachi launches CO2 heat pump water heaters with solar-f... by notrustincloud on Thursday September 10, 2026 @11:21PM (#49653166)
i briefly lived in a house that had second floor laundry with no tray or floor drain. the first day after installing a new washing machine it flooded and did over 30k damage to carpet, drywall, and installed electrical. Insurance would not cover installing a floor drain or tray, and the owner chose to let that decision stand.

truly bizarre

Re:Hitachi launches CO2 heat pump water heaters with solar-f... by Gibbon1 on Friday September 11, 2026 @02:57AM (#49654478)
Considering that US houses usually either have a crawl space, basement, or are on a slab the lack of a drain is weird when you think about it. You would think wet locations would be required to have a drain.

I think a lot of European houses have floor drains in the bath, you can basically hose the bathroom down.

More on topic. Outside of the US R290 (propane) heat pumps are common. But illegal in the US because the refrigerant manufacturers control the code bodies. You can have a 20lb propane tank hanging off a BBQ which in normal operation is literally on fire. But you can't have an R290 monoblack cause it's too dangerous.

Re:Hitachi launches CO2 heat pump water heaters with solar-f... by eru on Monday September 14, 2026 @01:23AM (#49692332)
> I think a lot of European houses have floor drains in the bath, you can basically hose the bathroom down.

Weirdly, in the UK it's common to have carpet in the bathrooms.