24/7 some one is desperate for clean safe drinking water for little to no cost.
With sterilized sand, charcoal, pop bottles and a coupler you can make potable water.
This is a device that allows one to use two used beverage bottles as a gravity water filter.
The coupler solves the problem of leakage between the connection of two bottles when one bottle is coupled upside down, and on top of a second bottle. A water tight seal is required.
The anti-leaking is accomplished with the addition of a simple angled (wedge) surface located at the middle of the coupler. The rim of the bottle compresses into the wedge and forms a waterproof seal.
edit: 9/3/13 update added PCO1881 Closure. This design attempts to meet the ISBT standards, Finish No. PCO-1881-0. This is the most widely used pop bottle thread.
I included a "Stash Plug" to seal the coupler. Inside the plug is a small pocket with an 1 mm O-ring grove. I will add the cover when it's finished. I may change the stash ring, and eliminate the O-ring in favor of a snap fit.
I added a small eating fork to the end of the Stash Carry Ring. The fork stores inside of the pop bottle neck. Spoon, and knife to follow. I will redesign these to improve the function, ease of printing, and robustness.
Adding simple utilitarian devices to the gravity water filter coupler will make the coupler more valuable to the user. Being of more value, it will be stored in a more memorable location, and in times of a disaster it's location will more easily be recalled.
There is a small lanyard loop which allow you to attach the bottle to the coupler so you don't loose it. The lanyard loop is also useful as a key ring bob, and it's small size makes it easy to always carry it with you.
The exterior is fluted to allow soft water soaked hands to obtain a confident hold of the coupler.
The part is designed for 3d printing with one end rounded, and the other end flat.
A flat is naturally formed on the outside wall of the closure to provide clearance for the lanyard. The flat area can be used for identification. It can be marked with a pen, a scribe, or with the tip of a solder gun.
The coupler is printed in a bright color like yellow or orange so it's easy to find if it's dropped.
I envision the gravity fed water filter being used unattended.
Unattended water filtration requires a reliable, and rugged coupler to prevent water from leaking. A threaded coupler was chosen over competing options such as an internal plug because it won't fall apart.
A straight walled plug inserted into the inside diameter of the bottle opening would be a precarious connection. This is due to the finish of the neck of the bottle being a reverse taper. A straight walled plug coupler would tend to creep out over time, this would cause a spill of a valuable resource.
Tubing placed over the outside diameter of the bottle threads would most likely leak immediately.
A threaded coupler provides a reliable leak proof connection, and a universally understood means of attachment (a plastic bottle thread).
It might be possible to make a cold cast (plastic casting resin) of the coupler for a moderate sized production run. If there is interest in this I can modify the internal thread, and the exterior to have draft to help release a cold cast part from a mold.
"Designs should advance, directly or indirectly, the safety, wellbeing, and performance of all people"
The gravity fed water filter promotes safety and wellbeing when used as an emergency water filter in a disaster area. Having a supply of sanitized water promotes peace by removing the fear of not having a source of clean drinking water.
Collect two pop bottles.
Cut the bottom off of one of the bottles.
Connect the two bottles together with the coupler.
Fill the upper bottle half full with charcoal.
Fill the remaining half with sand.
Place a piece of cloth over the sand to act as a pre-filter.
Pour water in and wait for it to filter through.
To prepare the sand:
Bake the sand in an oven at 250 F, for 3 hours.
To prepare the charcoal:
Place the charcoal in a sock and pound until it is a powder.
You want the water to flow through the charcoal, not around it.
In disaster areas instructions could be posted in key locations, and broadcast over the radio of how to make a gravity water filter.
I've left the design open due to the varied bottle threads that are available.
I will include two of the more popular bottle closure styles the PCO1881, and the PCO1810.
The thread that I have drawn presently was measured from a common bottle, but may not fit all styles of threads.
I plan to investigate if I'm able to integrate multiple thread forms into one generic thread profile.
After reviewing my original design (Gravity_Water_Filter_Coupler_v1.stl) to the PCO1881 closure (thread) I discovered that the length of the bottle neck, compared to the depth of the sealing surface within the closure leaves minimal room for over tightening. The overall length needs to be shorten to provide clearance. I have provided a new drawing that follows the PCO1881 standard. I'm deleting my original drawing to avoid confusion.
Link to CAD drawings (.pdf) of bottle cap closure:
There are thousands of references to gravity fed water filters.
I'm unsure of the original source of this idea.
I would like your feed back to further improve the coupler design. For example should I add a raised boss to the center of the coupler. A raised boss would allow creating a 3-way connection.
Print the coupler and assemble it on different bottles, and tell me what you discover. Please send me a private message (PM) if you feel it will be a distraction in the comments area..