I do enjoy a bath ... and the water is often shared, BUT - A lot of hot water is still let away.
In winter / heating season, could this easily (ie cheaply) be re-used?

I could let it go cold in the bathroom, but that would be bad bad bad for humidity...
I could maybe have a plastic cover over the bath, so it gives out heat as it cools down, WITHOUT releasing steam ....
What about having an old radiator in the room below, on the bathwater waste? - bath empties through the radiator, transferes some heat, used for heating the room below?
I imagine the ecosystem inside that old radiator could become quite unhealthy ...

Am doing a full refit, and just wondered ....
any ideas

yes, but it would be great to have a giant elasticated cover to slip over and keep the steam in....

Water left in the bath cools mostly by evaporation.

Tony has MHRV, so he can recover a little of the bath heat as the latent heat when the water vapour condenses in his exchanger.

I only have an extractor fan, so I have to waste extra electricity to vent out the humidity, I get the bath drained and squeegeed as quick as possible after bathing several children in it, as infrequently as is decent.

A 100 litre bath cooled from say 30degC to room temp contains 100* 4.2 * 10 /3600 = about 1 kWh of heat, worth about 6p, depending how you heat the house, so I couldn't justify spending big money on plumbing to recover it.

(Edit: However if it were cooled close to the incoming mains water temperature, it could release twice as much energy - ie pre heat the cold feed to the hot water system)

Others have made homebrew pipe in pipe exchangers to heat the cold feed to their shower using the waste, but we can't store the recovered heat for next week's bath like this...!

Check out Tim's pics http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=3050

If you just lift the plug a little and let the water trickle out, the slow flow of water would probably give up much/most of its heat into the internal waste pipes??

ah! for the days of cast-iron bath-tubs - none of this acrylic stuff !

gg

Insulating a bath is a good thing to do, since it reduces the hot water draw needed to keep the tub hot, and it also minimises the total energy used, whether in winter or summer.

Or a couple of bits of used packaging

"Insulating a bath is a good thing to do, since it reduces the hot water draw needed to keep the tub hot, and it also minimises the total energy used, whether in winter or summer."

We spent a lot on our bath but don't regret the investment - made of this stuff https://www.cabuchon.com/cabuchon-quality/#ficore which they claim "keep the water hot over six times longer than acrylic and over twelve times longer than vitreous enamelled metal"

I was dubious but it really seems to work - It is very noticable how warm the water remains even after a long bath.

Whats the best way of getting the same effect with a bath made of another material? Just stuff the space underneath with mineral wool?

Posted By: Simon StillWhats the best way of getting the same effect with a bath made of another material? Just stuff the space underneath with mineral wool?

That's what I did with our plastic bath, although with recycled plastic wool IIRC - easier on the hands. I doubt there's anything you can do with a metal bath except replace it - the conductivity is so high that heat will just move to the exposed surfaces.

<blockquote><cite>Posted By: owlman</cite><blockquote><cite>Posted By: tony</cite>Leaving water in the bath is the simplest and best idea.</blockquote>

<blockquote><cite>Posted By: wellburn</cite>yes, but it would be great to have a giant elasticated cover to slip over and keep the steam in....</blockquote>

A few quids worth of this may help?

<a href="https://www.poolandspacentre.co.uk/products/geo-bubble-pool-covers.html?gclid=EAIaIQobChMI8ru77ZnD4QIVi-F3Ch1aWgPPEAQYAyABEgJeoPD_BwE" rel="nofollow">https://www.poolandspacentre.co.uk/products/geo-bubble-pool-covers.html?gclid=EAIaIQobChMI8ru77ZnD4QIVi-F3Ch1aWgPPEAQYAyABEgJeoPD_BwE</a></blockquote>



I've sometimes thought about that, but the problem with a floating cover is that the surface area varies a lot depending on the water depth, as the sides slope.
I like the idea of an elasticated cover - perfect for a free-standing roll-top bath.

It doesn't really need to insulate at all, just be non-breathable so that water vapour can't escape. The heat would escape into the house, but the moisture would be contained.
It would be especially useful when sharing baths with a delay between users.

There are comments regarding insulation or foam to keep in the heat.

How about a Japanese bath? I would have loved to install one but the logistics were too difficult and the bath b***dy expensive in the UK.

First off, a Japanese bathroom is a wet-room and they don't have the same waterproofing issues that we in the UK appear to have. It is a wet-room and the systems are set up to make it watertight from the get-go. I tanking, etc is not a problem as the way it is built / installed, it is pre-tanked.

Basically, you have a shower outside the bath, splashing copious amounts of water around and then get into the bath for a good soak. You so not get soap onto the tub under any circumstances.

But the essential thing regarding this thread, is that the bath water is generally re-used for a few days, since it is essentially clean. A cover is generally used to retain as much heat as possible, but pre-bath, a gas heater is fired up to heat the water in the bath.

Pretty much like a jacuzzi in-line heater, but much more efficient. It will bring the bath up to temp in around ten minutes (give or take) The heater is externally mounted and has no pumps; convection circulates the hot water. The heater my parents-in-law have is on an external wall, adjacent to the bath and is small; not much larger than a small suitcase (like those that air crew use.)

I found that gas safety rules here in the UK prevented me from install a Japanese style heater. I was advised that it would be 'unsafe.' Of course, it is SO unsafe that X million Japanese have been using this system for many decades and it is not a problem.

Leave water in the bath, empty when cold, sheet of poly on top if worried about steam.

Shower let water fill tray and leave to cool the same

Water regs are a real pain to get round on this.

CAT tried a tank and it all went wrong years ago