Lesson 1: How To Water Your Garden Using Bathtub Water

By Grover Koelpin No comments


We are using a siphon to water our garden with bathtub water. Someone had recently taken a bath, so the bathtub was full. We began by detaching the shower head from the shower hose. Next we connected one end of the garden hose to the shower hose. We turned on the shower water and left it on for several seconds. The other end of the garden hose was outside in our garden. Once the water started flowing outside, We disconnected the garden hose from the shower hose, covering it with our hand. Then we turned off the shower water. We submerged the hose in the bathtub water. The hose went outside through the window on the other side of our house. We used the grey water to water our orange tree. [Water hose sound] Let’s go back into the house to see what’s going on in there. This is the end of our grey water supply. [[Air rushing into hose sound]] Now for a quick physics lesson We are using both gravity and air pressure to cause the water to go up and then down through the tube, in this case a garden hose. The siphon tube must start by being full of water. The water at the surface of the cup always has air pressure pushing down on it. According to Newton’s third law, each action must have an equal and opposite reaction. The reaction to the air pressure pushing down is the water pressure pushing up. Because the water pressure is pushing out in all directions, one place it can push is on the siphon Meanwhile, water pressure is also pushing down from the left end of the siphon. The upward water pressure is marked in green, because it is contributing to the siphon flow, and the downward water pressure is marked in orange because it is preventing the siphon flow. On the right side, upward air pressure is marked in orange, because it is preventing the siphon flow, and a greater amount of downward water pressure is marked in green, because it is contributing to the siphon flow. The total of the green forces happens to be greater than the total of the orange forces. Because on each side, the downward force is greater than the upward force, you might be wondering why the water doesn’t split in the middle and fall down in each cup. This would create a vacuum between the two regions of water in the tube. The water pressure closes the area in between. Therefore, the water can only flow in one direction, and it flows in the direction of the greater net force. If you plan on trying the project, here are some pointers. Number 1: Make sure that the garden hose is fully submerged in the water after you disconnect it from the shower hose. No air should get into the garden hose or it will not work. Number 2: The outside end of the hose must be below the end in the bathtub. Otherwise the siphon will not work. Number 3: When taking a bath or shower that you plan to use for grey water, it is best to use only biodegradable products. They are healthier for your garden, and will not pollute groundwater. Voice -“Dude, you gotta do at least some physics today” [Water plop] The sustainable backyard Simple environmental projects to create the perfect garden.

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