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The siphon principle

When we disconnect water from a tank, or add water from a bucket to a tank slowly, we are often indebted to this principle. But, what is the siphon principle?

Water flows to low

Everything around us is attracted to the earth. Unless give energy from the outside, objects basically fall. Also liquid such as water flows to the lower and the lower. This is known as gravity. A river flows, an apple falls -- these are due to this force. However, in the case of liquid such as water, we can twist the direction part of the falling with using a hose.

 

Make a path of water using a hose

1. Relationship between the atmospheric pressure and water in the hose

大気圧の関係Let's take a look. The right illustration shows the state of flushing out water from the bucket using the hose. The surface of water in the bucket takes certain atmospheric pressure (arrow 'A' in the illustration). At this time, the surface of water in the hose also takes the atmospheric pressure (arrow 'B'). These two pressures are equal regardless of area, so we can ignore them.

 

2. Water's tug of war

ホース内の水の動き#1Next, look at how the water in the hose works. As mentioned at the previous part, water flows to the lower. Based on this assumption, let's take a look at the water in the hose. On the right illustration, for the water of right side (red goldfishes) divided by the black dashed line, the lower is the right exit of the hose. Thus, the water of right side (red goldfishes) tries to fall in the direction of the red arrow.

On the other hand, for the water of left side (black goldfishes), the lower is the left exit. Therefore the water of left side (black goldfishes) tries to fall in the direction of the black arrow. However, the falling of the left side is end at the surface of the bucket water due to water pressure. Of the black goldfishes towards the bucket, the fourth black goldfish under the surface of bucket water isn't able to fall any more, because of the obstruction by the fifth one entering the hose from the bucket.

Then, which side the water in the hose will fall towards? The result is owing to 'tug of war' between red and black goldfishes.

 

3. Movement of the water in the hose - Part 1

ホース内の水の動き#2Try to move a little up the water in the hose of right side, and see what happened. The result is shown in the right illustration. Two red goldfishes towards the right side, and three black goldfishes to the left. Therefore the winner of tug is the black goldfish team, and the water in the hose falls towards the bucket. The hose doesn't have a gap, so the red goldfishes are dragged by the blacks and fall to the bucket, too.

 

4. Movement of the water in the hose - Part 2

ホース内の水の動き#3And next, move a little down the water in the hose of right side. The result is that the four red goldfishes towards the right side, and the three black goldfishes to the left, shown in the right illustration. This time, the winner is the red team. The water in the hose falls towards the opposite side of the bucket.

 

5. The siphon principle

サイフォンの原理Well, let's see the black goldfishes being dragged by the reds. At first time, the black goldfishes aimed to the left exit of the hose. And the reason of the black goldfishes falling towards the left is that, for the blacks, the left exit of the hose is lower than the right (already explained at '2. Water's tug of war'). But the lower side is switched to the right when a black goldfish goes over the top of the hose. The black goldfish that is across the black dashed line falls towards the right exit of the hose, as the red goldfishes are. If it becomes in this way, the black goldfish which was across the dashed line aides the reds, from the next to the next, and the water flows out from the bucket continuously. This is the siphon principle.

 

 

Cleaning a fish tank using the siphon principle

It is easy to clean a fish tank using a bucket and a hose, with the siphon principle.

1. Setting a hose into the tank

サイフォンの原理で掃除#1First, set a bucket just below a tank in order to receive the water unplugged from the tank. Even if you set the tank outside the house such as garden, you should use a bucket. This is for grasping how much water you drained from the tank. Also the bucket may save a small goldfish that you accidentally inhaled by a hose.

When you are ready for the bucket, then put a hose in the tank. At this time, you put the length of the hose into the water longer enough. The most part of the hose sink into the water, so you can attract a lot of water inside the hose.

 

2. Withdraw from the tank while closing outlet of the hose

サイフォンの原理で掃除#2Seal the outlet of the hose with plugging a finger into, or squashing it, and pull up the hose about half from the tank. Since the exit of the hose is closed, the water in the hose is also pulled up with it. However, if the outlet of the hose is not closed firmly, air will enter from a gap and the water in the hose will return to the tank. Take notice of sealing the outlet firmly with wetting a finger, or squashing the hose tight.

 

3. Bent the hose and turn the exit into the bucket

サイフォンの原理で掃除#3Guide the exit into the bucket while sealing it. Also the water in the hose is guided with the hose, you make for the water surface in the hose to come below the water surface of the tank. Specifically, you make the state same as '4. Movement of the water in the hose - Part 2 / Make the path of the water using a hose'. Now the condition of the siphon principle is ready to start. Release the exit of the hose in the bucket, and the water in the tank will flow continuously.

 

4. Suck out the garbage in the tank

サイフォンの原理で掃除#4Lead the hose and suck out the garbage at the bottom of the tank while the water in the tank is flowing. You can adjust the momentum of the water with squashing the hose moderately by another hand. If you suck out the gravel, don't be panicked, squash the hose tightly. The water flowing in the hose will stop, and gravel to be sucked out will return into the tank by weight. About the gravel which is sucked out into the bucket, return to the tank after rinsing lightly.

 

5. Disconnect the hose from the tank

 If the bucket fills soon, squash the hose tightly and stop sucking of the water. And disconnect the hose from the tank, throw away into the bucket of the water remaining in the hose, you are finished.

Be careful not to flood the bucket to be absorbed in sucking of garbage. When there is much quantity of the water in the tank, work in several times --- don't be strained.