After the suggestion of using mylar balloons as emergency water bags was made some time back, I went out and bought some at a local grocery store. They sold the large 18" ones deflated, but the smaller 9" & 4" ones only came inflated. I got an 18" round one, a 9" round one and an 18" heart shaped one (on the premise that, turned upside down, it would have a broad base and narrow "spout"). The 4" ones didn't look like they'd hold a useful amount, but I ended up being surprised how much these things held, so I may go back and get one, just for the pursuit of knowledge.<br><br>First, I began by testing the 18" round one.<br><br>Getting water into these things is tough! The necks are tiny and tight. I had to stick a piece of teflon tubing down the neck to pour water through. Small passage = small flow. Obviously, this was an unacceptable situation.<br><br>Getting the water back out is even tougher! They have one-way valves in their necks to prevent air from coming back out as they are inflated. It works real well against water too. Too well. But, I found that if I stuck the same length of teflon tubing down the throat, I could get the water out easier, and sometimes, I could drag the valve out around the tube and rip it out. Drinking out of the bag became easier after that was done.<br><br>I put some water in it and let it sit around for a few days. I hung it, I dropped it (lightly), I laid it down in many different positions (spout down, spout up, spout to the side) and it never leaked. Then, I opened it up and checked the quality of the water. Drinking it was not bad at all. The water had stayed clean, whereas water that sits in my mil-spec 1qt canteen starts to taste like plastic after some time. So, I feel that part was a success.<br><br>After all this messing around with it, I finally just snipped the neck off in the middle. That opened the passage up some little bit, and I could fill it more easily by swishing it back and forth underwater, as Doug says he does with condoms.<br><br>Snipping the neck completely off of the round ones makes them much like an open oven bag, I suppose, in that you have to tie the whole top portion to seal it. Snipping the heart shaped one was better. The slimmer portion near the top of the inverted heart made tying easier. I twisted the top of the heart shaped one and tied it with a twist tie. It worked great except when held upside down, whereupon it began to very slowwwly unwind/untie itself, just due to the weight of the water. Not bad, all in all, but certainly not up to any abuse at all.<br>So, note to self: Tie the large ones in a knot.<br><br>One thing about snipping the necks off:<br>Mylar is tough, but once cut (or, presumably, torn), rips like wet tissue. I destroyed the 18" round one by the time I was done. In order to avoid this with the others, I put a strip of electrical tape on both sides across the top of the balloon just below the neck, and then cut (into the tape with the large heart shaped one, just above it with the small round one). That worked great, but made knot tying more interesting.<br><br>The 18" bags are just freaking big! They hold a LOT of water! It makes them pretty heavy, and rather unwieldy. I got about 200oz into the 18" round one (roughly 6000ml), about 235oz into the 18" heart shaped one (roughly 7000ml). The biggest problem with them was that they were larger and heavier than my infant nephews. Seriously, I would be scared to carry them, expecting them to burst if I squeezed them too hard. And it seems a waste to carry such a large bag/balloon and only plan on using part of its capacity. Better to carry a smaller bag/balloon and fill it completely.<br><br>The 9" round one held 40oz (just under 1200ml) when held shut with a twist tie. When I tried to tie a knot in it, that amount fell dramatically to about 12 great big whopping ounces (350ml). <br>So, note to self: Use a twist tie for the small ones.<br><br>About paint:<br>Whether tying with a twist tie or into a knot, I twisted the top of the balloon around tightly first. This had the effect of stripping the paint off! After tying the spout to seal it, and then untying it to drink, the mylar was clear and the electrical tape had become painted the color of the balloon! Ugh! Drinking dried paint off the spout of my emergency water bottle doesn't seem like a particularly wise idea, but maybe I won't care in a true survival situation. Nevertheless, it's enough to convince me to continue to pursue other options.<br><br>I'd be interested in hearing other results.<br><br>Stay safe,<br>J.T.