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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

#21

Post by Someone1234 »

wcoenen wrote: post #7

I tried this once on a cold winter day: I let the bath cool down to room temperature (which was <20C) before letting it drain, with the bathroom door open. The result was a lot of condensation on the windows in the surrounding rooms. I figured the high humidity was going to cause more damage than it saved money, so I scrapped the idea.

Although higher humidity should make it feel warmer given the same ambient temperature. So if you're increasing the temperature mildly using this method AND increasing humidity, it may compound one another positively.

Although, it is a minor efficiency gain either way.

Re: Re-using the heat in bathwater in Britain

#22

Post by yrgulation »

Energy poverty can be sorted out by better insulation and investment in cheaper and more sustainable sources such as nuclear, wind and solar. Instead of working around this issue with clever hacks this needs to be a national policy. I think all roofs should be mandated to have solar panels installed, as a start, and all new builds should have proper insulation.

Re: Re-using the heat in bathwater in Britain

#23

Post by VBprogrammer »

convolvatron wrote: post #9

I reuse my bathwater to start a new load of laundry...that seems a lot simpler

How does the plumbing work for that? I can't imagine it passing plumbing regulations in most countries. Even having a grey water system is tricky under most regulations (the reason for this is the slim chance someone could misconnect a potable system.

Re: Re-using the heat in bathwater in Britain

#24

Post by bausgwi678 »

yjftsjthsd-h wrote: post #10
sweettea wrote: post #6

Not discussed: hot water in houses increases humidity. In modern well sealed houses, that can result in unfortunate mold growth.

I've always experienced extremely low humidity in winter months, so I would think the net effect might be a reasonable positive if this saves me needing to run a humidifier. Am I missing some detail? Or is that just unusual?

It depends massively on your climate and how air in your house is managed.

If you live somewhere which is significantly colder outside than in (e.g. 0-5C out, 21C inside) heating outside air to comfortable temperatures will greatly decrease humidity. Couple this with a system which circulates air, or even exchanges inside&outside air and you will have incredibly low humidity inside.

I live somewhere which often sees 10-15C @ 80% humidity over winter, and the only air circulation in my house is from opening doors/windows. 70% internal humidity @21C is incredibly common. It takes a bit of moisture management to keep it below 60%.

Re: Re-using the heat in bathwater in Britain

#26

Post by yjftsjthsd-h »

jibbit wrote: post #20
yjftsjthsd-h wrote: post #10

Earlier quoted context omitted.

I've always experienced extremely low humidity in winter months, so I would think the net effect might be a reasonable positive if this saves me needing to run a humidifier. Am I missing some detail? Or is that just unusual?

You’re in the uk?

No, but I was given to understand that winter => cold => dry air was driven by the basic physical properties, so I would be very curious if it was different there. Is it different in the UK, and if so, why?

Re: Re-using the heat in bathwater in Britain

#27

Post by VBprogrammer »

yrgulation wrote: post #22

Energy poverty can be sorted out by better insulation and investment in cheaper and more sustainable sources such as nuclear, wind and solar. Instead of working around this issue with clever hacks this needs to be a national policy. I think all roofs should be mandated to have solar panels installed, as a start, and all new builds should have proper insulation.

I think a step further is required. I really like the idea of using solar panels as an integral part of the roofing structure. There are people in the UK doing this as integrated solar panels which use a plastic tray underneath. I think with some slight adaptions we could even do better.

Re: Re-using the heat in bathwater in Britain

#28

Post by georgeg23 »

wcoenen wrote: post #7

I tried this once on a cold winter day: I let the bath cool down to room temperature (which was <20C) before letting it drain, with the bathroom door open. The result was a lot of condensation on the windows in the surrounding rooms. I figured the high humidity was going to cause more damage than it saved money, so I scrapped the idea.

You could place a plastic mat on top to limit evaporation.

Re: Re-using the heat in bathwater in Britain

#29

Post by ars »

throwaway894345 wrote: post #14
convolvatron wrote: post #9

I reuse my bathwater to start a new load of laundry...that seems a lot simpler

Not if you have a frontload washer. :)

Along with the problem of getting the water into the machine, the soap from a bath would damage the machine.

Front Loaders require low-sudsing soap, and you have to be very careful on the type of soap, because many types tend to precipitate onto the inside of the machine.

Re: Re-using the heat in bathwater in Britain

#30

Post by joezydeco »

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.

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