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Re-using the heat in bathwater in Britain

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Re: Re-using the heat in bathwater in Britain

#101

Post by bombcar »

joezydeco wrote: post #30

These diagrams imply that the incoming water to the heater is heated by drain water from the bath. But if you're filling a bathtub there's no warm water going down the drain. So the exchanger is useless here. And then when you're done and drain the tub the exchanger gets hot but the heater isn't filling any more. This device only really works in a shower situation, it seems.

The only "practical" installation I've seen (besides ones in massive multiplayer showers like you'd see at a college or YMCA) was for a massive house with a huge shower designed for 30+ minute showers.

And at that point you probably can "save the environment" more by not building a 10k sq ft mansion. But what do I know?

Re: Re-using the heat in bathwater in Britain

#102

Post by Gigachad »

jitl wrote: post #38

I read a lot about district heating systems yesterday after seeing an article on NYC's steam system on HN ( https://news.ycombinator.com/item?id=33388473 ). District heating systems allow you to capture waste heat at the power plant (called co-generation), and use that to heat & cool (via cooling compressors) many, many buildings at once. The wikipedia article about it is very informative as well: https://en.wikipedi…

Why not feed that heat back in to the power plant to squeeze more electricity from it?

Re: Re-using the heat in bathwater in Britain

#103

Post by twic »

pbhjpbhj wrote: post #83
upsidesinclude wrote: post #69

Turning your thermostat down by one or two degrees per week and getting acclamation to cold is a better alternative. 5 degrees on the thermostat would be a far better measure than tub heat. Short showers, or 'sea showers', to conserve water and heating would likewise be a far better option than a 50 gallon bath.

What's a "sea shower". Do you mean when you literally just spray water on yourself, then soap all over, then rinse off?

https://en.wikipedia.org/wiki/Navy_shower

Re: Re-using the heat in bathwater in Britain

#104

Post by sokoloff »

nsteel wrote: post #87
jitl wrote: post #38

I read a lot about district heating systems yesterday after seeing an article on NYC's steam system on HN ( https://news.ycombinator.com/item?id=33388473 ). District heating systems allow you to capture waste heat at the power plant (called co-generation), and use that to heat & cool (via cooling compressors) many, many buildings at once. The wikipedia article about it is very informative as well: https://en.wikipedi…

The problem with district heat schemes in the UK (at least) is they are becoming mandatory for new large housing developments but are 100% unregulated every step of the way. The builders do the cheapest job possible because the efficiency targets they're supposed to hit are never measured or verified post install. And unlike the rest of domestic energy in the UK, pricing is totally unregulated. The residents can (and…

It seems sabotaged by incompetence on the part of regulators. You can’t make something both 100% mandatory and unregulated and then go shocked-Pikachu when the monopoly grantee takes advantage.

Re: Re-using the heat in bathwater in Britain

#105

Post by erik_seaberg »

twic wrote: post #103
pbhjpbhj wrote: post #83

Earlier quoted context omitted.

What's a "sea shower". Do you mean when you literally just spray water on yourself, then soap all over, then rinse off?

https://en.wikipedia.org/wiki/Navy_shower

Tom Clancy loved to collect details like this. When Jonesy detected the Red October on sonar, in the book he was rewarded with a “Hollywood shower.”

Re: Re-using the heat in bathwater in Britain

#106

Post by ip26 »

twic wrote: post #96
maherbeg wrote: post #11

I was actually looking at heat recuperation systems for bathrooms recently and stumbled upon https://ecodrain.com/en/ - if we hadn’t already remodeled our bathrooms I’d have loved to have installed this. For now we make do with a heat pump water heater which is very efficient.

There are numerous manufacturers of these things, eg: https://powerpipehr.co.uk/ https://showersave.com/vertical-wwhrs/ https://recoupwwhrs.co.uk/ Ultimately they're just cleverly arranged copper pipes, so the barrier to entry for new manufacturers is low! I am keen to get one - my shower sits directly above a cupboard on the floor below, where it would be simplicity itself to fit. This article suggests the energy sa…

It depends heavily on how much your house showers, what the water temperature is at the inlet to the house, and how ideal your plumbing is. The efficiency is highest with a vertical unit at least five feet in length, and that’s really just down to your house’s layout.

Re: Re-using the heat in bathwater in Britain

#107

Post by nicd »

This reminds me of a "re-circulating shower" concept I was looking into recently. By filtering and re-using shower water, it saves both water and heating energy. There is a company in Sweden doing this: https://orbital-systems.com/.

There's a bit of an ick factor, but with filtration, it seems this should be more hygienic than bathing? My family remains unconvinced though ;)

Re: Re-using the heat in bathwater in Britain

#108

Post by oliwarner »

Having read this, I'm strongly considering routing my bath and shower wastes through a poorly insulated hot water cylinder in reverse (new [warm] waste in at the top, old cold waste out the bottom). Hot water will float in there. Cold will be displaced first.

It only has to hold the volume of "a shower" and we'd keep that energy within the envelope of the house, without added humidity or state-change heat loss.

The only major downside is the "what happens when it clogs" question. To work normally, it would require the discharge to rise to the same height as the top inlet before falling to the drain, but there could be a secondary purge for pressure-flushing it once a month.

Rarely does plumbing make so much sense to me. I suspect I'm overlooking something. Answers on a postcard.

Re: Re-using the heat in bathwater in Britain

#110

Post by afandian »

shellfishgene wrote: post #76
afandian wrote: post #40

Earlier quoted context omitted.

I wonder how different it would be to use an off the shelf heat exchanger, e.g. this one? https://www.ebay.co.uk/itm/263272702860 You'd probably have to filter the shower water before sending it through, but beyond that I wonder how different the principle is. Maybe being easy to clean is a significant factor in drain showers.

There may also be problems with sanitation rules, only a minimum of water should sit in the pipes, and then ideally hot our cold but not luke warm.

Got a link (or explanation) for that temperature stipulation?
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