Half a croissant, on a plate, with a sign in front of it saying '50c'
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Keeps the bath water warm.
  (+14, -4)(+14, -4)
(+14, -4)
  [vote for,

1) Relax in bath 2) Let some water out. 3) Add hot water. (When evetuallt the hot statr coming through) 4) Repeat 5) Next person to have a bath moans because there is no hot water cos you used it all.

A simple *cheap* (yes I know a jacuzi may do this) device to pump water from the bath, gently reheat it (not boil it!) and pump it back to the bath again.

With removable cleanable liner between element and water to make washing easy. Only difficulty I can see... no electrity in the bathroom. Maybe run off of 12 volt battery self contained and rechargeable.

CasaLoco, Feb 21 2002

Conair Dual Jet Bath Spa http://www.walmart....290%3A77957%3A50134
A "device that plugs in the mains and goes in your bath". One of hundreds. [waugsqueke, Feb 25 2002]

Conair Thermal Spa Bath Mat http://www.walmart....637%3A77957%3A50134
Uses heated bubbles instead of heating/recirculating the water. This is what I was thinking of in response to phoenix's anno. [waugsqueke, Feb 25 2002]

Livestock water tank heaters http://www.enasco.c...m+%26+Ranch&seqid=4
They *might* work in a tub [runforrestrun, Feb 25 2002, last modified Oct 04 2004]

(??) It's the yellow one http://www.heat-therm.com/htprod.htm
'Might doesn't fit in a student's flat. [halfmanhalfcookie, Apr 28 2002, last modified Oct 04 2004]

Archive: It's the yellow one https://web.archive...herm.com/htprod.htm
Might doesn't fit in a student's flat. [a1, Nov 29 2023]

History https://en.wikipedi...History,-%5Bedit%5D
[a1, Nov 29 2023]


       Hm. Candles are popular during relaxing baths; candles produce heat; of all places I'd think it safe to have a candle, in the bath is pretty high.   

       Especially if you have a bathroom without electricity <valgal>omiGAWD!</valgal>, fire might be your best heat.
hello_c, Feb 21 2002

       You can buy coffee reheaters that dangle in your cup and warm your coffee (they look a bit like a kettle element). Half a dozen of these in your bath should do the trick.
dare99, Feb 21 2002

       Someone needs to post an idea that is a combination of this (bath heater) and the tub cushion. Anyone? Anyone?
phoenix, Feb 21 2002

       Those exist, phoenix.   

       CL, you have no electricity in your bathroom?
waugsqueke, Feb 21 2002

       Assuming you have power (I think most people do, otherwise it would be very dark) build a bathtub with heater elements embedded in the ceramic. Similar to the heated floor systems.   

       Surprised this doesn't exist already!
rbl, Feb 21 2002

       Or get a swimming pool. Or light a fire under your bath, cannibal/explorer style.   

       Re power in bathrooms: planning regulations in the UK mean you can't have regular electric sockets in a bathroom, only specially isolated shaver sockets and appliances directly wired in. The USA doesn't have planning regulations, because of the constitutionally-guaranteed freedom to use your hairdryer in the shower if you like.
pottedstu, Feb 21 2002

       I have searched, both last night and this morning for anything resembling what is described here (an inexpensive recirculating bath heater [not a jacuzzi]) and I have yet to find anything. Maybe my search string is bogus, but all I can find is aquarium heaters and, well, I suppose you could use a bunch o' those.
bristolz, Feb 21 2002

       (Tosses [pottedstu] into the tub with a large American blowdryer)   

       We require GFCI outlets within 3 or 5 feet of a water tap (kitchen, laundry, bath, etc) too.
phoenix, Feb 21 2002

       [PeterSealy] - Not all houses have direct action water heaters. (Heaters that heat water as you use it.) Many houses have the far more effecient Hot Water Boiler which heats a big tank of water, then you use it, then you have to wait for the next lot to heat up. Either way you gotta run the taps for a while before hot water come out... eeek cold water!   

       [Hello_C] - Candles wont heat the bath water.   

       [Dare99] - An ok Idea but you need a large array of 12v batteries to run them off. PLus you will burn yourself on them if you accidently touch them.   

       [rbl] - In order to keep the water at a stead temperature the bathtub wuld have to get quite hot... hot enough to burn you if you touched it. Water cools very quickly especally in the form of steam... thats why you sweat.   

       [pottedStu] - thanks for saving me from having to explain it.   

       [Bristolz] - they would still require mains electric. They are also not very efficient.   

       [All] - Ya know.. I'm sure if I patented my idea and started building them I could sell these...
CasaLoco, Feb 21 2002

       CasaLoco: Yes you might be able to get a market. Maybe propane canister powered?
bristolz, Feb 21 2002

       Interesting idea.   

       When I read this, I thought it would be a kind of thermostat in the bathtub which you could adjust to a temperature of your liking - oh, say, seventy degrees or so; and, when the water got too cool, the bath would automatically either use a heating element to warm it up, or automatically drain some of the water and turn the faucet on until the water was at the desired temperature again.
Pseudonym #3, Feb 21 2002

       At 70F you'd be pretty darn cold and at 70C you'd be coddled.
bristolz, Feb 22 2002

       I think that you've definitely identified a gap in the market here, CasaLoco. I could do with one of these as it's no fun trying to read a book in a cold bath. Perhaps we should all be bathing in a fluid with better heat retaining properties than water?
DrBob, Feb 22 2002

       I imagine that would be custard.
angel, Feb 22 2002

       Is there really a 'not-a-Jacuzzi' market for this, though? It seems to me that those desiring this would also want jets and would probably go for the spa tub. (I've done a lot of investigation into this sort of thing recently - upcoming bathroom renovation.)   

       CL, I've got to believe that the number of households with no electricity in the bathroom (save for third world countries) is extremely small, and certainly not worth a special product design.
waugsqueke, Feb 22 2002

       I meant fahrenheit, just to clarify. But now that I think of it, it probably would be rather cold. Or luke warm, at best. I imagine most of you are Brits, and have abandoned the idiotic use of the fahrenheit scale we Americans seem to cling so desperately to... if only our government wasn't so disfunctional. Oh well.
Pseudonym #3, Feb 24 2002

       Removable cleanable liner -- yes.
Use excess power to run a dehumidifier.
reensure, Feb 24 2002

       waugs has a point. If you're adding a system to pump water out, heat it and pump it back in, you may as well make it do jacuzzi stuff.   

       If all you want is a heating element in the tub, I think you'd have problems burning yourself on it, since it would have to be significantly hotter than the water to heat it.
pottedstu, Feb 24 2002

       I think it'd be pretty easy to burn yourself on it...   

       Don't necessarily need a pump. Old 'Mother Earth News' magazine had a hot tub heater that was a backless D shaped pipe with a heater in the center. Cold water comes in the bottom, is heated in the center and rises, coming out of the top. It wouldn't be sufficient to actually pump water anywhere, but for just recirculating, it'd work fine.
StarChaser, Feb 24 2002

       Or a microwave emiter down at the tap end. This could be built into the structure of the bath, without making any potentially leaky holes and wouldn't roast you alive unless you got within about 4-8cm of it. (or get some tin foil bath shoes).
dare99, Feb 25 2002

       Could you have a bath within a bath.. leaving an inch wide gap between the two, and having loads of little micro sized holes so that the water could flow between... the heating elements could be built into the outer layer, leaving the inner layer only as warm as the water and using rubber bungs to seperate them. Then you could have a thermostat setting to keep the temperature at the level you wanted.. Am I missing something really obvious here?   

       Also, it would be fun to put springs inbetween your inner and outer baths... bath suspension!
Danzarak, Feb 25 2002

       It'd be a bitch to clean, you'd have to disassemble it.
dare99, Feb 25 2002

       If it was just a thickish plastic casing that slotted in, you could take it out to clean the inside... you could even hose the outer bath down if you wanted.
Danzarak, Feb 25 2002

       [Bristolz] - Nice idea which I already though about but there would be gas leaks and carbon monooxided to contend with, plus the hassle of buying gas for it. Theory is to have something you just rechearge in a normal power socket.   

       [waugsqueke] - You've missed the point... A) Most people don't want to remodel their bathroom just to have a bath that stays warm and B) I don't care what electric you have running into your bathroom I couldn't care if you have pylons running in through the window, there is no way any device that plugs in the mains and goes in your bath will ever get a safety certificate. Showers are a special exception with special rules as they are specially sealed, isolated and are non-movable.   

       [Reensure] - What excess power? Aim is to make is as effifient as possible to allow most possible use from a single charge.   

       [Starchaser] - It can't go in the bathtub... most bathtus are cramped enough already.   

       [Dr Bob] - Sadly most heat retaining fluids are either not very fluid, are corrosive, toxic or release toxic vapours, or would leave an unsierable reside.   

       [Angal] - Custard isn't a bad idea... I may post that as another suggestion...   

       [Dare99/Danzarak] - No Remodelling!   

       [All] - the main aim of this idea/design is to give you the feature with minumum running cost, zero changes to the bathroom, and zero risk. I am going to look into the possibility of patenting this... there must be a market for it... I don't know anyone who doesn't enjoy a long bath...
CasaLoco, Feb 25 2002

       // Most people don't want to remodel their bathroom just to have a bath that stays warm //   

       If you're going to assert that, I'd like some data to back it up. I can't prove the opposite, granted, but again, if you want warm, why wouldn't you want jets? Most jet tubs are available with a recirculating water heater as an option. So, since people buy jet tubs and add heat, as opposed to buying heat tubs and adding jets, it seems to me more people want jets than want heat.   

       Makes sense to me. Jet tubs aren't that expensive, and many will fit in the same space as occupied by the existing tub. Of course, you'll need electricity to run it, which leads to...   

       // and B) I don't care what electric you have running into your bathroom I couldn't care if you have pylons running in through the window, there is no way any device that plugs in the mains and goes in your bath will ever get a safety certificate. //   

       Yes way. CL, you are quite clearly off the mark here. See links (including one that almost bakes this idea, in fact, it would qualify as Sealy-baked).
waugsqueke, Feb 25 2002

       A couple of things wrong with what people are saying: First, water does not lose heat quickly. It is actually a material treasured for its ability to store vast quantities of energy. Water has a high specific heat, this means that it requires large heat gain/loss to change the temperature of water. Unlike a heat conductor such as a metal that requires very little heat to change temperature. So a different liquid is bunk. Water is pretty close to the best choice. Consider the passive solar heating craze of the '70s.   

       Second: Heat loss/gain from one body to another is a function of delta. This means that the apparently fast heating/cooling of a bathtub which is a small body of water (45-90 gallons) compared to the volume of the room. Consider the temperature difference of the room and you have a lot of water evaporation and heat leaving your bath. Therefore, the best way to keep the bath hot is to minimize delta, that is, heat the room to its max relative humidity near the temperature of your bath and the water will not cool. A simple space heater for half an hour before pouring the bath should bring it up to temp.
BeastMaster, Feb 25 2002

       Okeydoke. Two ideas free for the taking. They're not very good ones so I'm not being that generous.   

       1) Since most of the heat of the bath is lost by evaporation (it's the hottest water that escapes as steam leaving you with the tepid stuff) you could lay a waterproof 'bath blanket' over yourself. I really don't like the idea of bathing with a rubber sheet on the surface of the water, but it would keep the bath warmer for longer.   

       2) I like this one but feel it's coing to be impractical: Construct a low voltage waterproofed heater run on as many AA cells as it needs. There is no pump - the heat is disipated by convection (or just general swirling in the bath). I get the feeling that you're going to need more AA cells than makes this practical but if someone can work out the heat loss of a bath at their favourite temperature we can work out just how impractical this would be.   

       (1 AA cell can give out about 6000J during its life. If the bath loses heat at the rate of 100W then you need 1 AA cell per minute of bathtime. If the bath loses heat at the rate of 1KW then you need 1 AA cell per six seconds of bathtime. I knew this would be impractical.)
st3f, Feb 25 2002

       CasaLoco: What I mentioned is outside the bath, not inside. An opening low for the cooler water to come in, and an opening high but beneath the surface for the water to go out, in a closed loop. The pipe itself is outside, and heated by something <heat tape, solar panels, rubbing hamsters together, whatever> and natural convection makes the water circulate slowly.
StarChaser, Feb 25 2002

       Anybody who wants one, I'll build and install it in your existing bathtub for about $600 USD, plus travel and lodging expenses. [basically I'd follow the plan by DeGroof]. Makes me think . . .
quarterbaker, Feb 25 2002

       st3f: would bubble bath work as an alternative insulator?
pottedstu, Feb 26 2002

st3f, Feb 26 2002

       [pseudonym], the trouble with Celcius is that it's lousy at incremental degrees, 'cause the scale is so large. "Today's temperature will take a tumble to a slightly chilly 17.2 degrees, but will warm up tomorrow to a more comfortable 20.1." I rather prefer the increased precision efficiency of the Fahrenheit system to having a convenient point at which water freezes.
RayfordSteele, Feb 26 2002

       [waugsqueke] - Remodelling if you add together all the people who can't afford to remodel their bathroom, don't want to remodel their bathroom, can't remodel their bathroom due to building restrictions and people who live in rented accomodation then I am pretty sure you would get a large enough group of people to call most.   

       Most safety organisations are against anything which brings mains electric into the bathroom in a portable device. Maybe some people make some devices that pass the legal checks... doesn't make them really safe.   

       The idea is only baked if you are able to install a jacuzi tub. If you can't do thet then it isn't.   

       [BeastMaster] - try heating the bathroom to keep the water warm... you will pass out or at a minimum you will be very uncomfortable.   

       [st3f] - Bath blanket is a nice idea and works the same way as outdoor swimmingpool covers.   

       [StarChaser] - Kinda works however convection would only work if the heating element was below the level of the surface of the water and the pipes went in through the side of the bath... remember... convection causes water to flow but will not cause it to flow above the water level. Unless I'm misunderstanding the highschool science I did 10 years ago.   

       [pottedstu] - If you could get a thick enough layer of bubbles covering the whole surface of the water if would act as a good insulator because "air is a bad conductor of heat energy"....
CasaLoco, Feb 26 2002

       // Most safety organisations are against anything which brings mains electric into the bathroom in a portable device. Maybe some people make some devices that pass the legal checks... doesn't make them really safe. //   

       These things are everywhere. I’m sure there totally safe when used properly. (Did you even see the links?)   

       // The idea is only baked if you are able to install a jacuzi tub. If you can't do thet then it isn't. //   

       I was never claiming your idea is baked. I was merely questioning how large a market exists for it. It seems like a simple device to manufacture. And there are many varieties of devices which skit around this function but do not do exactly it. That suggests to me this is because the potential manufacturers don’t see a market for it.
waugsqueke, Feb 26 2002

       How about simply building a thermostatically-controlled heater underneath the bathtub? If the tub itself were heated, that would keep the water warm. If the tub had to be able to heat a tubfull of cold water in any reasonable time, the surface of the tub would need to be uncomfortably hot. If the goal was merely to counteract convective and evaporative heat loss, however, direct conduction should suffice even without a large temperature gradient.
supercat, Feb 27 2002

       --> 4) Repeat means 5) Next person can use the same water, aha. That's ecologically benefical. I suggest to sell also camouflage coloured bath-tubs (another golden idea) especially for martial people. I promise, when the water is going swampy after one or two month, they will automatically step to 1).
halfmanhalfcookie, Apr 28 2002

       pottedstu: Does H.M. Government really forbid outlets in bathrooms in the U.K.? Have they never heard of ground fault circuit interrupters?   

       My personal thinking is that the best thing to do would be to wrap some heating cable around the perimeter of the underside of the bathtub. That would eliminate all but evaporative losses (which may or may not be significant depending upon water temperature and ambient humidity). If one had to eliminate those as well, some bubble bath should do the trick.
supercat, Apr 29 2002

       Baked, in Japan. My aunt has one, it's really deep and it takes about 15 minutes to heat up. You set the temperature on an electronic keypad, clean yourself off, then get in to soak... exactly how it works is a mystery to me.
Blackanese, May 03 2002

       This is a particularly great idea because: A] Baths should last practically forever, and B] Baths are always too damn hot when you get in, and frigid a few minutes later when your temperature regulation system acclimatises to the new environment. A warm bath that gradually cooks you, in the manner of the oblivious frog of legend, would pretty much perfect my spiritual survivial kit.
Mharr, May 10 2002

       This is pretty much how virtually all Japanese home baths have been working for decades. It's usually reheated by natural gas, and most washing machines are capable of reusing bath waste water.
rhatta, Apr 02 2009

       It turns out I invented the hot tub.
CasaLoco, Nov 29 2023

       // I invented the hot tub //   

       I dunno about that. You might want to review the history link and see where your innovation fits in the timeline.
a1, Nov 29 2023


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