The Toddler Water Wall is the kind of slow backyard project that grows one empty plastic bottle at a time. We started ours in May with three bottles screwed onto the back fence. By the first really warm weekend in June we were up to fifteen. Adam at two years and one month old was the chief inspector and chief water-pourer. The Update post is here to show what fifteen bottles look like together and to write down the small physics moment that came out of it.
What the water wall is made of:
- Around fifteen empty clear plastic drink bottles in mixed shapes and sizes. The variety is the best part. Tall slim bottles drop water in a long ribbon; squat fizzy-drink bottles dump it in a single splash. Wash and dry every bottle properly before you start.
- A sharp knife or kitchen scissors for cutting the bottom off each bottle. The cut does not need to be neat.
- One screw per bottle, plus a washer, driven through the side of the bottle into the fence panel. The washer keeps the soft plastic from tearing around the screw.
- A screwdriver. Cordless is faster but a hand screwdriver also works for fifteen screws if you take a coffee break in the middle.
- A black plastic tub or wash basin to sit at the bottom and catch the runoff. Anything wide and shallow works.
- Two or three small plastic scoops, cups, and a watering can. The kid uses whatever is in the sandbox bucket anyway.
Building it up bottle by bottle
Cut the bottom off each bottle. Hold a bottle against the fence at an angle so it tips slightly forward, screw it through the upper side of the bottle into the panel. The cap stays on, with a small hole drilled or punched through it so water trickles out the bottom of the bottle and into the open mouth of the next bottle below. Position the next bottle so its opening sits directly under the cap above. Then the next, and so on, working diagonally across the fence in a rough zig-zag.
Fifteen bottles takes about an hour with a small kid running back and forth carrying the bottles to you. The cuts get faster as you find the right angle. The trickiest part is positioning each new bottle so the water hits cleanly into the next opening rather than splashing off to the side. We had to re-screw three of ours after the first test run. The fence wood is soft and forgives a second hole next to the first.
Pouring and the bottle-top trick
Top up the watering can. Hand it to the kid. Stand back. The first run sends water cascading through every bottle and out into the tub at the bottom. Adam refilled the watering can from the tub and ran it through again, and again, for about forty minutes before sitting down on the grass to study the wall in silence.
The small kid-physics moment came on the second afternoon. Adam dropped a loose bottle top into the open end of one of the upper bottles. Water hit the bottle top and slowed visibly, pooling around the obstacle before threading past. He looked at me, looked back, dropped a second bottle top into a different bottle, and watched again. He had no language for what was happening but he had clearly noticed something. Two-year-old experimentation, unprompted.
For another small kitchen-science moment that runs along similar lines, our Frozen Vinegar Rainbow Fish activity freezes vinegar in fish-shaped trays with food coloring, then sets the fish on baking soda and lets the kid watch the fizz reaction. Same age, same kind of stop-and-stare attention.
The wall stays up all summer. By August we usually have twenty-something bottles, with bigger ones replacing the small ones that have warped from sun. We take the whole thing down for the winter and put it back up in May the next year. Three summers in and the screws have left a polite line of small holes across one fence panel, which is the actual cost of the activity. For a smaller outdoor activity that packs into a bag for the beach, our Seaside Car Track Busy Bag uses painted lolly sticks and laminated road signs that fit in a sunglasses case.
One closing observation. The cap with a small hole punched through is the part that took us the longest to get right. Too small a hole and the bottle fills up and overflows around the cap. Too big and the water shoots through too fast for the kid to see anything happening. About the diameter of a thick nail is right. We tested three different cap-hole sizes before settling.