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File: shower heat exchanger.png (108 KB, 810x782)
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In Finland, majority of energy costs comes from heating, and majority of that from water heaters. And majority of hot water is used by the shower. So when water from the mains comes in at between +1 and +8 degrees and used water leaves at +37 degrees, recovering some of that heat ought to mean massive savings in energy bills.

I found this video about how to make such a heat exchanger yourself, so I'd like to know /diy/'s opinions on this: https://youtu.be/I4wO3tjoQpw?si=hK0rpD0h3Cc53POY

How long would the exchanger need to be? Should I do it myself or are there better commercial versions already? Any other thoughts or recommendations?
>>
Not worth the trouble
>>
The hot shower water is already cooled by mixing cold water with it. The cold water flowing thru the heat exchanger will cool it even further.
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https://www.energy.gov/energysaver/drain-water-heat-recovery

there are commercial products that exist for this
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>>2757207
>The hot shower water is already cooled by mixing cold water with it.
Are you stupid? Some hot water is MIXED with some cold water.
>The cold water flowing thru the heat exchanger will cool it even further.
Cold? It will be lukewarm and it's meant to preheat the water supply of the water heater. Am I just responding to bait?
>>
Oh look honey we saved .37 cents on gas last month.

>>2757216
Wah bitch
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>>2757217
At least I can comprehend what a fucking water mixer is.
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>>2757201
This is retarded penny pinching savings. Why dont you get insulated triple plane windows instead.
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>>2757201
that wouldnt work and it would also be unsanitary...how very finnish of you
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kek everyone too retarded to see its drain waste water heat recovery.
in theory it works, but in practice you will save maybe 1 cent in a year. And have fun cleaning that shit up.
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>>2757220
Still whining
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>>2757206
>Not worth the trouble
The average heating bills from January have been on average 400 euros. If you managed to somehow cut down just a quarter of that, it'll be an extra 100 euros per winter month every year. Very worth it if you ask me.
>>2757233
>This is retarded penny pinching savings. Why dont you get insulated triple plane windows instead.
That's a lot of money. Also, insulated windows have been a standard in Finland for decades.
>>2757207
>The hot shower water is already cooled by mixing cold water with it. The cold water flowing thru the heat exchanger will cool it even further.
The idea is to recapture heat from the used shower water before it flows out of the house, and using that to preheat the replacement water coming into the water heater.
>>2757208
Thanks! This and a shower version would be perfect. It's good to know they're already available, although ordering them from America would cost a fortune in shipping.
>>2757225
>that wouldnt work and it would also be unsanitary...how very finnish of you
How so? Waste water flows in its own straight pipe out the house, and the incoming clean water in its own pipe around it.
>>2757240
>kek everyone too retarded to see its drain waste water heat recovery.
in theory it works, but in practice you will save maybe 1 cent in a year. And have fun cleaning that shit up.
That's exactly what I'm looking for. You'd think it saves more than that considering the heat difference between incoming water (in Finnish winter) and waste water. And why would it need more cleaning than a straight pipe without another pipe around it?
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>>2757258
Pure speculation with regards to savings
Lets see some data bitch that likes to argue
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>>2757258
< The idea is to recapture heat from the used shower water before it flows out of the house, and using that to preheat the replacement water coming into the water heater.

No shit Sherlock. The drain water from shower will be cooled by the cold water in the exchanger. Its a trade off. Not to mention the used water from shower wont be that hot to begin with derp derp
>>
That heat exhangern is gonna foul like a motherfucker. Hair, dirt, soap, cum....
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>>2757262
Exactly. I just had to explain it because >>2757207 didn't seem to get it.
And lukewarm water is still easily 15-30 degrees warmer than the 1-8 degree warm water coming in.
>>2757264
Again, how is it any different from a plain straight pipe? Only the clean water twists around while the waste pipe goes straight through the exchanger.
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>>2757201
If your shower is also a bathtub, just plug the drain while showering, and then let the water sit till it reaches room temperature.
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>>2757201
Quesition: won't the lukewarm mixed water near heat exchangers make for prime habitat for legionella?
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>>2757260
Fairly easy to calculate; we know the specific heat capacity of water, and we know how many liter-degrees we're going to save per minute, so now you'll just need to plug in the electricity prices (4-250 cents/kWh depending on day)
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>>2757278
The air temperature is about 20 degrees, while the water from the underground mains is less than ten. Even room temperature water holds plenty of energy compared to the water coming in.
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>>2757217
Must be nice to heat water with energy dense cheap gas. Let me tell you resistive heating just ain't worth it.
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>>2757240
>in theory it works, but in practice you will save maybe 1 cent in a year.
Waste water treatment plants do it for profit on commercial scale. There's lots of energy in hot water
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>>2757317
The lukewarm mixed water flows out of the house, dissipating heat as it passes through the heat exchanger. Cold, fresh water flows in, preheats in the heat exchanger, and then goes into the water heater to be heated up to full temperature.
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>>2757201
>finland, a country with more geothermal than most of the world but are so leftist they need a 2nd mortgage to afford electricity.
If youre so crazy about it why not apply the same garbage tech thats mostly suited for your coastal country and use a heat pump as an exchanger? Then you can really virtue signal as you save a couple of cents of heat for even more expensive electricity. Awww shit stick a peltier device and feed back a couple of watt-seconds into the grid.
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One or two 30 minute showers a day equates to pennies in btu energy. If that.
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>>2757328
I mean the cold water is in the loop, and if it's not flowing, it'll stay in the loop until more water comes in
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>>2757334
An inline-heated shower can take 15kW of power. If you combine it with some unfortunate prices (like 2,5€/kWh two weeks ago) you'll be taking 30€ showers a day.
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>>2757201
Wrong.
The heat exchanger goes on the side of the tank. The circulating water enters the bottom of the side arm and flows up.
Buy your side arm according to the measurement between the blow off valve and the tank drain. If the heat exchanger is too long, the length needs to be added at the bottom by lowerign the tank drain, not by lifting the pop off.
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>>2757331
>>finland, a country with more geothermal than most
...that's Greenland.
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File: 2310476.jpg (134 KB, 960x640)
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>>2757350
We did try geothermal on commercial scale, but after drilling a hole for about 4 miles the water was still lukewarm. Couple hundred million down the drain.
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>>2757340
That same water stays in straight pipes too. And because it goes into the water heater, it will be heated hot enough to kill legionella before being used anyway.
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>>2757201
Your basic premise is wrong - if the water is coming into your house at 1 C, this means your ground temp is 1C and your average air temp is 1C aka you have cold winters and you are spending most of your energy on heating, not showers.
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>>2757366
>Your basic premise is wrong - if the water is coming into your house at 1 C, this means your ground temp is 1C and your average air temp is 1C aka you have cold winters and you are spending most of your energy on heating, not showers.
Water has four times the heat capacity of air, which is why it takes much more energy to heat it. It's why liquid cooling is so much more powerful than air cooling, and in this case it would be cooling the house instead of a motor or a computer.

I'm sorry, but is 4chan experiencing some kind of retard season? I've never had to explain so many, so basic things in one thread before.
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>>2757350
>>2757360
>hurr durr we suck at geothermal
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>>2757388
Yeah. The 4 mile deep hole was one of those so called 'great potential' sites. You can make educated guesses on paper, that's cheap, but once you have to invest hundreds of millions into realizing a dud, not many are willing.
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>>2757363
It could be, depending on your heater size and setup, but it could also be used before it gets time to cook
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>>2757383
>It's why liquid cooling is so much more powerful than air cooling
It's not any more powerful than the other side dissipating the heat somewhere else. You can have several better air-cooled PC setups simply because thet all eventually cool down the same way. Water just works like a heat capacitor to smooth out bumps
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>>2757395
At least in Finland, water heaters fill up from the bottom and drain from the top, to make sure only the hot water gets used. If so much water is taken out that the temperature starts to drop too much, there is another electric coil at the top to heat the water as it exits the tank too.
>>2757396
Is this bait? Are you getting off to this? Just chomp down on a mouthful of winter air and a mouthful of snow and tell me which takes longer to heat to body temperature.
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>>2757423
The air in your mouth isn't moving, like the air around the fins of a CPU cooler.

But more importantly, you are saying but are just to dumb to realize it.
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>>2757201
you'll never recover the cost of setup
you're better off investing in heat pumps and on-demand water heaters
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>>2757423
>there is another electric coil at the top to heat the water as it exits the tank too
They aren't both activated at once, but the top one switches on instead of bottom one to cope and give a couple minutes more until you're completely out of warm water.
>>
>>2757423
>Just chomp down on a mouthful of winter air and a mouthful of snow and tell me which takes longer to heat to body temperature.
And which one takes longer to cool back down? There aren't any free rides out there. If you got a closed loop the only real matter is how you're going to exchange heat. The absorbing material is just there as a filler.
>>
>>2757206
FPBP
I did the calculations on this a few years ago for my own home while I was studying energy management. It's really, honestly not worth it. If you have electric instantaneous hot water and pay variable rates for electricity, install a water storage heater and program the element to only come on at cheap times. That's the $2k solution that will pay for itself over a few years. I don't personally recommend a hot water heat pump, that's a $5k solution that may not pay for itself over its lifetime due to increased maintenance costs and low efficiency in Finland's climate.
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Nobody mentioned that it'd be more efficient if the cold water entered the heat exchanger from the right...
>>
Just buy a hybrid heat pump water heater you dumb fag. That'll cut energy usage by 60% right there.
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>>2757360

did you consider putting some type of water heater at the bottom to warm it? just a thought..
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>>2757201
https://www.jlconline.com/how-to/plumbing/wastewater-heat-recovery-systems_o
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>>2757763
Thanks, this is exactly what I've been talking about.

I even found a shop selling these in Finland, and a square model that goes directly under the shower seems ridiculously easy to install. The pipe-shaped ones appear to be even better, but they all seem to require a vertical installation. Considering I've never seen a non-apartment building with shower on the second floor in Finland, I wonder how much efficiency the pipe version would lose if installed horizontally?
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>>2757258
Finn, let me give you some advice. It seems to me your problem is with finding cheap energy. You see, nature has provided the answer for that. Go outside. What do you see?

Trees. Plenty of them. Chop one down, set it on fire. What do you have?

Heat. See what I'm getting at? Now you just need a way to apply that heat to water. Yep, there's your hot water. How much did it cost?

Nothing.

You're welcome.
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>>2757622
>If you got a closed loop
what part of taking cold water from the mains, heating it, and putting it down the drain warm sounds like a closed loop to you?
>>
Most residential waste water heat recovery systems will never pay for themselves or recoup the energy + CO3 needed to manufacture them at any reasonable time scale. A system that actually is efficient as claimed will cost you more. The most common systems installed in Ontario are based on idealized if not outright falsified testing data. The government was lobbied to make them mandatory in new homes, pocketing the family that owns the manufacturing rights a lot of money.
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>>2758785
how many carbonate anions do you expect such a project to require
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>>2757258
Reburning water boiler stove combo.
Cut wood. Finland has a lot.

Sorry that being a eurobro is expensive. I have natural gas on the property and springwater, and am completely offgrid.

I think you would be better off having a heating loop circulating coolant that goes through conventional solar (not electric) radiators on the roof. It's an unpressurized system. Very safe. That will get you the additional heat you're looking for, without the risk of mixing sewer with freshwater, which, is, for sure, the reason why your suggested solution is not done. 100%: a ton of disease was solved by basic indoor plumbing, and keeping those two lines separate.

Keep the poopchute separate from the drinking water.
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>>2758751
Firewood is economical only if you own forest. If you have to buy wood, it'll generally be cheaper to buy electricity instead.
>>2758875
Solar collectors are good for most of the year, but there's hardly any sunlight over the four coldest months when the heating is most needed. Solar panels do good job reducing the electricity bill over the year, but in the cold and dark winter there's no light to power them either.
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>>2758778
That doesen't make water any better at cooling, you're just externalizing the process to somewhere else.
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>>2757201
In short, this is impossible and cannot be done.
As >>2757208 said there are solutions.

The problem is they must be part of the plan when doing construction/remodeling, and aren't really a quick "DIY" project.
There are many ways to more efficiently heat water than taking in pipeline water and having your heater heat that from cold to hot but this is something that benefits from having lots of area, not something you can fit in most homes if it wasn't part of the plan.

This is why commie blocks (large apartment buildings) are so efficient. When trying to min-max things for personal homes it becomes more difficult unless you're creating your own floor plan and can dedicate the square footage to such a thing.
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>>2757201
>In Finland, majority of energy costs comes from heating, and majority of that from water heaters.
Same problem here. Someone made what you propose, and also provides measurements:
https://sondred.info/varmegjenvinner.htm
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>>2759345
> Solar-heated water systems to boost inlet temp to the gas/electric water heater tank "are not as useful {or, I'll take your 'not useful at all'} for four months out of the year."

Bro, can you math? Useful for, with your proposal, 8 months (or 9, if 13 month calendar) with all the hot water needs being taken care of for ~4 of those.

You calculate savings averaged across the entire year. Solar water systems can be DIY'd. Although they'd be more effective with well established vendors, OP sounds like a penny-pincher. Circulation pump, coil of proper poly pipe, and some reservoir. I'm sure tons of diy guides exist.

> He's not in the woods
He should be. Are you not OP, and don't know anything about Finland's woods?

>>2759395
nailed it.
>>
I hope gorilla retard kike OP faggot builds his penny pincher constraption and posts results or fucks off already.
>>
File: heat-exchanger.jpg (429 KB, 1500x896)
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>>2757201
This is a vertical model. Probably more efficient.
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>>2759680
That definitely seems to be the most common model, they seem entirely unusable in Finland because no house has a shower high enough up to install a vertical pipe like that under it.

Pic related is a new idea I've been thinking of, using a tank of standing water that gets replaced with warm water as the shower is used. The downside is that the tank will be full of legionella and need to be manually emptied of any debris every few years, but the upside is that because just the top curve of the emptying pipe needs to be above the sewer pipe, the rest of the tank could extend much deeper into the floor.
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>>2759991
A warm tank a human waste water sounds like an awesome thing to keep in your house, maybe at the point the shower is over the tank will be warm enough to actually affect the temperature of the supply.
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>>2759680
i don't know how saturated the tube is that the water from the shower flows down. i don't think there would be all that much thermal contact. also the residence time isn't going to be great.
probably you'd want to have it at an angle, like OP's pic but at a slight angle. vertical model is going to be less efficient due to less residence time and less thermal contact.

things which are important to keep in mind: plastic is an insulator, the pipes are going to need to be something like aluminum or copper. corrosion concerns? can't put strong bases down the drain any more (lye drain cleaner, etc).
how difficult will it be to maintain? if something goes wrong, how devastating will that be? will you be able to tell if a leak happens? what if your graywater ends up in your water tank?
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>>2759680
Why do so many heat exchangers have the incoming water pipe spiraling around the outgoing pipe instead of going in one thick pipe like in OP's video? It has less metal between the two water flows, and I'd assume it's cheaper to use one thick outer pipe instead of loads and loads of thinner pipe that won't even be in full contact with the inner pipe from all points.
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>>2760568
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>>2759991
If you place the tank so it can be easily cleaned outside perhaps it could work, right?

>2760021
Yes, the human waste of grey water.
Maybe if you use black water the fermentation process actually warms up the water. Besides you might be able to catch off methane for your very own bio-gas.
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>>2757201
this was actually mentioned in thermo class so it's definitely a thing, but as others have said it's a question if it's really worth it. btw you can use a similar setup for regular heating where the outgoing air heats up the incoming fresh outside air, but that is next level
>How long would the exchanger need to be
if it's just two concentric pipes then it's pretty much the most basic heat exchanger you can imagine which is fairly easy to calculate
which i'm not going to do, fuck you. it's on wikipedia. useful knowledge though so you can now design your own stills as well to save even more money
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>>2759370
sorry can you say that again?
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>>2760568
>incoming water pipe spiraling around the outgoing pipe instead of going in one thick pipe like in OP's video

There isn't that much surface area on the outside of a plain pipe. A pipe-in-pipe heat exchanger would work okay, but not as well as it could. Imagine if you added a sort of sleeve that had fins to the inner pipe before covering it, increasing surface area to aid heat transfer. Look up what the inside of a water cooling block looks like for an idea of what that looks like.

The walls of the spiral square pipe are those fins. It's just easier to wrap and solder some small tubes around a larger one than it is to make a whole other part with a bunch of thin walls.
>>
I mean if you don't mind paying for all that copper and are pretty skilled with a torch it might be a fun project.
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>>2760572
Could someone explain this in pain English?
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>>2761212
seems to me like the temperature profiles in a heat exchanger with and without counter flow but i don't really get why that's relevant to what he responded to
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>>2757201
Air heat exchangers have been a thing for apartment complexes for a while now, but whether they'll be worth the price in a small house is still questionable. Weirdly enough I've never heard anything of water heat exchangers before, considering how much more thermal energy water carries and how much simpler something like that would be compared to building all the ductwork for an air system.
>>
>>2763037
a heat pump is something else entirely anon



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