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DIY drinking water filter that remineralizes and sterilizes condensation from air conditioning

Darko Savic
Darko Savic Jan 03, 2022
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A do-it-yourself filtration system that turns AC condensation water into the highest quality drinking water.
Turning air conditioning condensation into drinking water has been done before. The novelty of this idea is the DIY method that is specifically designed to meet the following criteria:
  • accessible to anyone (available components)
  • easiest to clean
  • durable with very low maintenance
  • prevents leaching of unwanted plastic/chemicals into the water
Provide your household with the cleanest possible drinking water. It's like having a natural water spring originating in your home.
How it works
Take 2 steel or copper pots. Stainless steel pressure cookers would be perfect because the lid can be tightly sealed. If you use a normal cooking pot you would have to figure out a way to tightly seal the lid on, but also make it easy to open for periodic cleaning.
Connect your air conditioning unit's condensation pipe into the first pressure cooker. To prevent upstream plastic leaching into the water, consider replacing the plastic pipe with a stainless steel or copper pipe. Use the same steel/copper pipes throughout the project.
Distilled water
AC condensation water is basically distilled water. It's missing minerals which makes it unfit for drinking. It pulls minerals from the surroundings - which could be the cells in your stomach/intestines.
Condensed (distilled) water accumulates in the first pressure cooker. Anything organic gets degraded by the UVC light that is mounted into the lid. This effectively kills/degrades any microorganisms and viruses.
When the water level reaches the overflow point, it continues into the 2nd pressure cooker. There the water is remineralized by passing through sand, rich in calcium, magnesium and sulfate.
This container has a built-in makeshift membrane in the middle. The membrane is open at the bottom. This makes it mandatory for the water to pass through the sand before reaching the overflow pipe.
Obviously don't use some chemical adhesive to hold the membrane in place. Welding would be nice, but it might not be a DIY option for everyone. What could hold the membrane in place and prevent the water from seeping through the sides?
Drinking water
When the container fills, it overflows into a stainless steel keg. Alternatively, it could also be a glass keg that is covered with something to prevent daylight from reaching the water. This container also includes a UVC light, to prevent any living organisms to survive inside.
Ideally, this keg is cooled. It has a built in tap that dispenses drinking water on demand.
With some clever piping, all the components can be hidden from view. Only the final keg with the tap is placed on a kitchen counter or built into a cabinet.

Potential weak points
Upstream chemical contamination
Potential unwanted chemicals can leach into the distilled water right at the source, when the water exists the air conditioning unit via plastic tubing.
With some effort, the tubing could be replaced with some kind of metal or glass tube. For example these flexible stainless steel pipes.
Resilient microorganisms
Hypothetically, resilient species of microorganisms could survive the UVC disinfection in the first holding pot and move on into the remineralization pot.
What if we drop a few tablets of beneficial probiotic bacteria into the reemineralization pot? They wouldn't have anything to eat in there other than other microorganisms that happen to float in. Just in case, they would also be killed off by another UVC light when they move on to the main dispenser tank.
Parts not accessible to everyone
Not everyone can order UV bulbs online. Flexible stainless steel pipes are not available in all parts of the world.
I'm sure with some work, people could figure out locally available alternatives. Even glass bottles could be cut, partially melted, and welded together to form tubes.
I can't (yet) come up with a good non-chemical UVC light bulb disinfection method. Well.. maybe heat and pressure would work. Since the first holding container is an actual pressure cooker, we might aswell use it and let it steam off into the cooling container.
No need for AC in wintertime
In the wintertime there is no need for cooling, so there is no condensation coming from the AC.
This is basically the same thing ac AC in reverse. It passively condenses water from indoor air in the wintertime.
No airconditioning
Not everyone has/uses air conditioning.
Add an additional pressure cooker and boil water in it. Let the steam condense into the next pressure cooker.
How to prevent microorganisms from entering the drinking water keg via the water overflow outlet?
One was is to make the excess water overflow from the first pressure cooker, right next to the UVC lamp. Anything that got close to the outlet would be irradiated by the UVC lamp.
Knowing that both UVC lamps are operational
How do you know that both UVC lamps are working fine? Eventually one of them would die. Since you don't see then, how will you know on time?
A marketable product
This could be made into a marketable product. I imagine a wider diameter stainless steel pipe, cut in half lengthwise. The upper part opens up to expose 3 compartments (UV, remineralization, cooled drinking). There is a tap built into the side of the 3rd compartment. You connect electricity to it and that's it. The entire thing should be wide enough for the 3rd compartment to hold enough water for the entire family/day.
The pipe could also be square. The initial condensation container can be just big enough to house the UVC light bulb. The remineralization container should be slightly bigger and the drinking water container should be the biggest.
You could then either:
  • Screw this on the side of the wall that has the AC above it, and drink from it
  • Mount it under the AC unit, connect a pump to it and pipeline it to where ever you want to mount the tap.

[1]Water, Sanitation and Health Protection and the Human Environment World Health Organization Geneva - ISBN 92 4 159398 9 (NLM classification: WA 687) - https://www.who.int/water_sanitation_health/dwq/nutrientsindw.pdf?ua=1#page=157

Creative contributions

Hide the components in a presentable keg

Darko Savic
Darko Savic Jan 03, 2022
The UVC light and the cooling coil make the dispensing container/keg ugly and unsafe to look at. However all the components could be hidden inside a countertop keg that looks like this:
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Simplified design

Darko Savic
Darko Savic Jan 03, 2022
Now that I think about it, there are many ways of simplifying the above design.
Only one pressure cooker is needed if you can separate it into a smaller area for the UVC and a bigger one for remineralization.

Basically something along these lines:
But replace lemons and ice with a small cup that holds the UVC lamp and overflows into a larger cup that holds the remineralization sand. Then everything overflows into the drinking-ready compartment with another UVC lamp in it.
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Stainless steel

Darko Savic
Darko Savic Jan 03, 2022
Just found this:
Distilled water is particularly corrosive. With no minerals to give the water pH balance, distilled water is absorbing chemicals (phthalates, bisphenols) from plastics, nickel from stainless steel, aluminum from aluminum containers, and carbon dioxide from the air.
So distilled water leaches nickel from stainless steel.
But also this:
Nickel is necessary in many organism's diets but can become carcinogenic and toxic in high doses. Women are more commonly allergic to nickel exposure than men. Exposure to skin can cause dermatitis upon contact. When ingested through water, in small amounts, it is harmless to humans and in fact necessary in our diet.
So.. maybe glass instead of stainless steel after all? But placed in a box so that no natural light gets to it.

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Drinking water cooling via the same AC unit that made the water

Darko Savic
Darko Savic Jan 03, 2022
Copper coil could be wrapped around the drinking water dispenser. It would be connected to the pipe that brings the coolant gas from the outdoor to the indoor AC unit.
Apparently, the refrigerant is just the right temperature for the water not to freeze even during prolonged operation of the AC unit.
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Remix of ideas

Darko Savic
Darko Savic Jan 03, 2022
Here's where my thought process is currently at:
  1. mount the AC unit in the highest feasible point in the house
  2. make the copper line that cools the indoor unit take a (downward) detour to wrap around the countertop water dispenser that's located in a convenient place. Probably kitchen. Then return (upward) to cool the indoor AC unit.
  3. hide the copper pipe that is wrapped around the water dispenser. Build it into house walls. Make the outer shell of the countertop water dispenser out of wood. Inside the wooden keg, wrap the copper pipe around a removable glass container. Thereby hiding it.
  4. The entire filtration could be built into the upper half of the inner glass container itself.
  5. The overflow can go straight out through the wall adjacent to the dispenser keg. The overflow pipe is hidden in the outside wall of the house and insulated to prevent it from freezing in the winter.
I have yet to figure out a way to use an air-to-air heat pump that cools the indoor AC in the summer (while producing water) and heats the radiators in the winter (while also producing water). It can't heat the radiators and cool the dispenser at the same time. So an alternative water cooling method would be necessary with the heat exchanger.
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UV-C light and ozone

Darko Savic
Darko Savic Jan 04, 2022
Apparently UV-C light knocks Oxygen (02) molecules apart, then some of them tend to link in threes to form Ozone (O3). Ozonated water can potentially be harmful.
That's a big problem. I was counting on the UV-C bulbs to make the water safe.

[1]Carmichael NG, Winder C, Borges SH, Backhouse BL, Lewis PD. Minireview: the health implications of water treatment with ozone. Life Sci. 1982 Jan 11;30(2):117-29. doi: 10.1016/0024-3205(82)90643-9. PMID: 7033710.

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jnikola2 years ago
There are plenty of alternatives to this.
For example, to remove organic, inorganic, and biological compounds from water carbon nanotubes (CNT)-based filters can be used. If coupled with acoustics that acts as a pressure source, it can give you an effective water purification system.
There is also the Aquaporin Inside technology in form of membranes that can be easily fitted inside small water purification systems. As in every water filtration system, you should eventually change the filters.
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General comments

Darko Savic
Darko Savic2 years ago
Drinking water made on the go, from car AC condensation. This is pretty cool:)
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Darko Savic
Darko Savic2 years ago
I'm going to build a commercial looking version of this:)
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