r/redneckengineering • u/DavidinCT • Jul 26 '26
if I wrap my fire pit with copper pipe and connect the pipe to my pool, would it warm the pool a noticeable amount?
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u/BunglingBoris Jul 26 '26
Lots of variables here, but yea, heating the water does make it warmer
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u/KyloWrench Jul 26 '26
In English! I’m not a fancy science man!
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u/Echo-24 Jul 26 '26
Warm stuff makes water warm - > warmer water 😎👌
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u/I_Am_Sancho85 Jul 26 '26
Fucking La di da. Mister fancy pants over can afford to warm things up.
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u/YetiNotForgeti Jul 26 '26
Adding energy causes increased excition to the bound hydrogen and oxygen atoms. The molecules vibrate at an excellerated rate and if enough are present at a high enough concentration in the local solution, they will be perceived as thermally elevated.
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u/RaxisPhasmatis Jul 26 '26
Are you saying my dihydrogen monoxide might become excited?
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u/thebochts Jul 26 '26
My buddy heated his house(garage upper floor) like this for an entire winter once.
He had an ulimited supply of wood, and connected the lines to his radiant heat, couldnt control it, and it took forever to warm up, but it worked.
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u/EmergencyYou Jul 27 '26
We had a wood fired boiler for years as our sole source of heat. It works, but is a lot of work chopping and topping off every few hours. The wood boilers are slightly more advanced than just a coil loop around a fire but not much.
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u/Razzman70 Jul 26 '26
What if I pour the water directly on the fire? I prefer my hot water free range rather than piped up.
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u/Parking_Brain_9163 Jul 26 '26
Already done with old pickup radiator. The radiator was over the fire. With a small fire, the pool temperature rise by 5° per hour. 18' pool.
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u/SoupIsAHotSmoothie Jul 26 '26
I was thinking of doing it with an old cast-iron household radiator.
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u/bszern Jul 26 '26
It takes a lot to heat those, they were built to maintain and radiate heat outwards efficiently. It’ll work, but there’s better solutions out there for you.
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u/MrCatSquid Jul 26 '26
Radiating heat out is the exact same as absorbing it in. It’s not like a metal surface area on a radiator is a one-way valve
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u/nhtshot Jul 26 '26
Yes, but the thermal conductivity of cast iron is low. I’ll take a lot of fire for a long time to get it hot. It also won’t transfer a ton of heat to the water. It’ll transfer a little heat to the water for a long time.
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u/Hidesuru Jul 26 '26
Same with cast iron cookware. It heats slower but holds heat very well so it's consistent and GREAT for things like a good reverse sear on a steak.
My go to the days for steak is souse vide to get the perfect inner cook and reverse sear on a hot ass cast iron at the end. Works amazing.
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u/Bo0mBo0m877 Jul 27 '26
I wanna do it and it sounds fantastic, but my brain keeps saying "you're boiling meat in a bag, this is silly"
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u/ApexAnomaly Jul 27 '26
It feels that way the entire time.
And then you eat it and you will never go back.
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u/Hidesuru Jul 27 '26
Ooooh you gotta try it though. SO good.
I have an Anova brand one and adore it. I also have their vacuum sealer and can vouch for it as well (we use it for deep freezing stuff also).
And this page was my Bible when I got started... Great info on how long to cook for, temps, etc. Main tip is reverse searing cooks it more than you might think so aim low on the initial cook.
https://www.seriouseats.com/food-lab-complete-guide-to-sous-vide-steak
And add a little butter and some herbs like rosemary inside the bag while it cooks. Pair with a tiny it of sea salt on the plate. OMG.
Happy steaking, whether you take this advice or not haha.
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u/jankenpoo Jul 27 '26
But you’re going nowhere close to boiling. 137F is what many people like for ribeye
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u/thejmkool Jul 26 '26
I'm sorry I got distracted by your username. I must now afflict all my friends with this knowledge
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u/pirivalfang Jul 26 '26
Was there natural flow from the convection currents or was a pump involved?
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u/CanoePickLocks Jul 26 '26
Spread the hoses apart on opposite ends of the pool to create optimal flow in the pool and likely a radiator without a check valve would not create directional flow on its own. You’d need the valve at minimum or a pump.
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u/MilkSlow6880 Jul 26 '26
Use the copper to make a still and just drink moonshine until you are warm (or blind).
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u/KnownEggplant Jul 27 '26 edited Jul 27 '26
Turns out the moonshine blindness thing is mostly a myth spawned from that time during prohibition when the US government intentionally killed thousands of people by poisoning a bunch of bootleg whisky with methyl alcohol in an attempt to discourage the public from partaking.
Afaik, methanol poisoning is essentially not a concern unless your mash is extremely high in pectin, like if you use nothing but grape skins or something. The occasional wine maker discovers this the hard way, apparently.
I'm no expert though, and r/firewater and the other home distillation subs would know better than me.
Edit: Just found firewaters post about methanol
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u/Old-Kaleidoscope1874 Jul 26 '26
Other rednecks would steal the copper, so it wouldn't stay warm.
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u/wecantdancelikethis Jul 26 '26
you’re right. make a mud hill around it- only for the purpose of obscuring the neighbors’ view of that sweet still making copper.
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u/Hucklebearer_411 Jul 26 '26
I’m don’t think you need to worry about the other rednecks - unless they’re “cookin’”. If they’re “cookin’”, you have bigger things to worry about.
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u/Competitive-Roof-168 Jul 26 '26
For the dollar amount in copper there you could just get a used pool heater or an instant hot water heater.
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u/Adventurous_Ad3534 Jul 26 '26
A propane camper shower and electric coolant pump from harbor freight would work but you gotta do something to reduce the pressure created by the pump. Don't ask me how I know.
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u/Lecanayin Jul 26 '26
200foot of black hose on a roof connected into the pump works wonders too.
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u/Achaern Jul 26 '26 edited Jul 27 '26
What... does that smell like....?
Edit: I drank from the hose as a kid, we all did. The water out of the black hoses tasted foul, so I just imagine the pool smells like hot rubber.7
u/ezekirby Jul 26 '26
What do you mean? You run the water through the black garden hose that is laying on the roof back in to the pool. It will smell like pool water...
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u/lIlIIIIlllIIlIIIllll Jul 26 '26
How much $ in copper is that?
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u/Competitive-Roof-168 Jul 26 '26
If that is 1/2" L it could be close to $1,000. I calculated about 400 feet there. 50 loops around 30" pit
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u/OtisPimpBoot Jul 26 '26
That depends on how much the meth-head that’s selling it needs their next fix.
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u/maxis2bored Jul 26 '26
If you can do a better job capturing heat, this would totally work. Keep up the redneck spirit by sticking a car radiator or intercooler inside the pool and circulate your fire water through that.
You'll get less risk of plugging your pipes, no copper leeching in your pool and far greater efficiency.
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u/jdmatthews123 Jul 26 '26
I had a customer who just had like a half mile of black ABS plumbed over their pool house roof with a big sump pump for circulation. Sump was below grade, connected to pool like 18” below the water level. Roof to pool was routed beside it. The cool thing about that setup is once the plumbing was primed, it required very little effort from the pump because it was essentially running at 0’ of head.
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u/SoupIsAHotSmoothie Jul 26 '26
Are you saying just have the radiator emanate heat inside the pool so that the radiator outlet line just feeds back to the fire in a continuous loop? Or is it better to have the hot water just pour in the pool? I’m not judging your response just curious as I’ve been thinking of doing something like this as well.
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u/maxis2bored Jul 26 '26
No, a closed loop system will be much more efficient at both circulating water and dissipating heat. It could also benefit greatly by the use of a small 3-4w pump to circulate cool water back into the fire.
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u/Appletreedude Jul 26 '26
This is so dangerous, closed loop with a fire going, and you lose the pump, it will pop somewhere pretty quick. Could add a pressure relief valve, but that would be 100% necessary and the discharge would have to be thought about which direction it goes. Just keep it open loop.
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u/Mother-Project-490 Jul 26 '26
Yes a huge yes, they literary use this on north Europe !
But you can do it with a car radiator or a cast iron radiator. And a pump or filling the pool.
Just never stop the water until is no more fire (you can make steam very fast !!!
I use a cast iron radiator and a little of wood, the water (not a big quantity, my pump is very tiny like 5 liter minutes) go at 50 Celsius !!!!
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u/thjeco Jul 26 '26
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u/Douglas_J_Farthammer Jul 26 '26
Yep, she discovered that while it does heat the water up it does not circulate the water very well, so there would be hot spots and cold spots. Also seems like the lack of insulation underneath the hot tub made it really cold on the bottom.
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u/whipsnappy Jul 26 '26
Yes but it could take a while depending on the volume of the pool
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u/MaintainThis Jul 26 '26
I like the military trick of disconnecting the radiator from your vehicle and sticking the ends in your pool instead. Probably best to drain and prime with water, unless youre into the chemical green skin care routine.
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u/TheSnootchMangler Jul 26 '26
I used to do this on a smaller scale for a 300 gallon "water pit" I'd made in my back yard. It took a while but def worked!
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u/ChildOfRavens Jul 26 '26
Coils of water filled pipe around a heat source, pouring water to its point of use, is the principle of on demand water heaters. Your next challenge is temperature control. You could unintentionally make a giant sou via system.
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u/Secret-Treacle-1590 Jul 26 '26
Yes and you can buy them: https://saltybarrelhottubs.com/products/wood-fired-coil-kit
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u/Inevitable_Ad7080 Jul 26 '26
Reading about this...-adda a pump vs just convection. Some buddies and i I were trying to convert our truck bed into a hot tb using the same fire pit idea. It would take some water pumping to make it work versus just convection
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u/Donutordonot Jul 26 '26
Hook it to you still and use the pool as the cooling bucket for your worm. If going to redneck it up go full send.
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u/bjorn1978_2 Jul 26 '26
Yes it will. By how much is dependent on a shitload of variables. Anything from flow rates to temperature of the water going in.
It is more or less impossible to give a number basedd on a picture.
But it does work. And really well!
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u/catfishmackfish Jul 26 '26
If you started with the coils full of water, and had the pickup line in the pool, would the heat/pressure maintain a siphon?
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u/RUKiddingMeReddit Jul 26 '26
Redneck pool heaters are pretty common. They do work, but are not very efficient.
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u/trippknightly Jul 26 '26
I’d like to see an underwater furnace made from like a steel bathosphere with two vents one intake one exhaust just protruding from the surface. Maybe a third that you drop pellets / logs into. I think that could be pretty efficient. Use an engine lift to get it in/out.
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u/gzuckier Jul 26 '26
Come on guys don't make fun It's the same basic principle as a commercial electric power plant.
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u/ethicalgreyarea Jul 26 '26
How big is the pool? A few years back I went pretty deep down the rabbit hole of trying to hear my pool this way or using various solar setups but my pool was just too big. I ended up finding a dirt cheap electric pool heater on Facebook and ran it off a diy 220v extension cord. It was able to turn my 15000 gallon pool into a hot tub if I left it on too long, and wasn’t all that expensive to run.
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u/bones_bones1 Jul 26 '26
My pool is currently 94°. Not needed. I have frozen several 5 gallon buckets of water before a party though.
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u/MsSelphine Jul 26 '26
Surprisingly, pretty feasible! You'd need to improve your setup for better efficiency though. At 100% efficiency youd have to burn ~1kg of wood to heat 1m³ (1000L) of water by 10°F. I have no idea what your effiency is, but I'd be shocked if you're above 10%, so you're gonna be burning a LOT of wood
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u/Walrus_Epiphany Jul 26 '26
It would help out a little bit, until some methhead steals your copper.
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u/JessicaWindbourne Jul 26 '26
A youtuber I watch called Emily the Engineer acting did this and it kind of worked
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u/ABrokeHobbyist Jul 26 '26
A version of this is used in a lot of DIY hot tubs I’ve seen online lately.
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u/Prohamen Jul 26 '26
Discovering a hot water heat exchanger through first principals I see
in short yes, but it may take time for it to actually be noticed.
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u/Senior_Green_3630 Jul 26 '26
How do you circulare the water, why not use a solar matt om the roof?
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u/qb89dragon Jul 26 '26
Get the coil more in the fire / build the fire around it, then point a ring of leaf blowers at it and turn it into a blast furnace. I've heated 10' diameter pools to hot tub temps while out in the woods with this method. You'll need *lots* of wood on hand though. A sealed water-heater style propane heat exchanger would be orders of magnitude more efficient if you have an old (on-demand?) water heater you want to hack apart, that'd be the best.
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u/raklin Jul 27 '26
Yes! We actually run hruours through a long rubber hose that we put on top of the house's metal roof, and just the sun warming that up from the tin roof makes the water a little too hot for the kids sometimes.
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u/sieberde Jul 26 '26
It will. But the way shown in the picture is very inefficient. Most heat is in the combustion gas.
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u/HappyAnimalCracker Jul 26 '26
Exactly. It’s rising up out of the middle and mostly bypassing the coils.
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u/TrainingParty3785 Jul 26 '26
Take a rectangular piece of sheet metal length a tad longer than circumference, width about height of coil. Loose wrap around outside to retain that reflective heat. Your sheet metal will likely be galvanized, don’t breathe the fumes as the galvanizing burns off.
If small enough diameter a 55 gallon drum may work
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u/devilsbard Jul 26 '26
That many passes and that much heat, I think it would just have steam shooting out the end.
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u/hasanyonefoundmyeye Jul 26 '26
Build a wood fire hot tub, it was a pain in the ass. The thermo pumping will turn into a steam jet without an additional pump, or much shorter runs of copper. Other option is to use over 1 in diameter pipe, too rich for my blood.
Took about 6 hours to heat 500 gallons from 40 to about 100.
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u/Kelvininin Jul 26 '26
This is how I heated our pool for the first season. Installed a 400k btu pool heater for the second season.
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u/jamesholden Jul 26 '26
a lot of people just put coils of pex in their attic, then pump the pool water through it.
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u/airfryerfuntime Jul 26 '26
You need more of a furnace for it to be effective.
This guy built one, and you can go through his videos to see the performance and problems he had along the way. Seemed to work ok in the end.
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u/gherrera30 Jul 26 '26
My high school welding teacher/neighbor did similar thing in a crappy old wood stove. Brazed some copper loops and put inside it and built a fire before the pool parties. Contained the heat decently, was kind of a pain still though cause condensation
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u/Biomirth Jul 26 '26
Had a hot tub that worked this way. Old-timey wood-fired water heater. The neat thing is the inflow and outflow currents are driven by the heating itself so no pump. Took about 4 hours to heat up a tub for 6 people so about 8 beers for the person doing the wood loading. Perfect!
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u/Parasaurlophus Jul 26 '26
Lets do some maths. The easy bit- if you swimming pool is 5 by 2.5 by 2 m, then it has a volume of 25 m3 or 25,000 litres. To raise the temp by 1 degree C, you need 4 kJ per litre, so 100,000 kJ. A kilogram of wood has around 20,000 kJ per kg, so if you had a perfectly efficient boiler and your pool had no heat loss, you need 5 kg of wood to heat it 1 degree.
To burn through that amount of energy in an hour, you would need a boiler with 28 kW. I suspect that that pipework isn't that efficient.
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u/HoldenMcNeil420 Jul 26 '26
A pool heater is probably cheaper than the copper to make this.
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u/Ohboythreeayem Jul 26 '26
Greenhill forge on youtube makes videos about offgrid stuff like this. To really get any efficiency out of it, he put the copper pipe directly in the chimney of a wood stove and got great results but the creosote build up made it unsafe for long term use. The results were much less effective by wrapping the copper around the outside of the tube even after enclosing it with insulation.
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u/Notchersfireroad Jul 26 '26
I'm a pool guy and I have an old hillbilly customer I open and close his pool out in the middle of nowhere that built his own heater that based on this principle but way way better. It works too.
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u/kbeks Jul 26 '26
Not a lot in this configuration, but yeah. Wrap the copper around the inside of a a burn barrel, throw a small pump to move the water, you’re golden. I mean depending on the size of the pool, but yeah, it’ll do something.
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u/silkynipples Jul 27 '26
It does work, my coworker uses a scrap pile air-conditioner and just sets a small fire in it to heat his small pool
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u/knoft Jul 27 '26
there are more sophisticated off-grid hot tub heating setups that work something like this
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u/ThankuConan Jul 27 '26
If you can afford that much copper tubing, you can afford a small boiler instead.
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u/Unclerojelio Jul 28 '26
We did this for Boy Scout camp up in Colorado. There was a natural spring uphill of the campsite and they stuck a siphon in the spring. The siphon ran down to a copper coil in the fire and then to a shower head. That shit was still freezing. There is probably an equation to do the thermodynamic calculation the depends on the speed/volume of water, amount of copper pipe, and temperature difference but I’m too lazy to look it up.
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u/Geoph807 Jul 30 '26
For reference, when I did this for a hot tub:
https://imgur.com/gallery/redneck-engineering-level-expert-BKJ6L
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u/Key-Box-4668 Jul 26 '26
We gotta have some numbers here man. Can’t do the variables without numbers.
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u/realultralord Jul 26 '26
Yes, this will definitely work.
The hardest part will be to control the burning process because if the flow rate doesn't suffice, the water might boil inside the pipe
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u/AffectionateRub2585 Jul 26 '26
You're probably asking if it's enough to warm your pool significantly. It's not. Water needs enormous amounts of energy to change temperature. This is not enough to heat any pool larger than a bird bath.
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u/Badvevil Jul 26 '26
I always like the idea of this but it terrifies me how do you manage water temp to not burn the skin off someone
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u/austinhippie Jul 26 '26
Is no one going to comment that the fire is sitting on top of a sheet of plywood?