water in the u-bend

[woody6]

how does water manage to travel over the u-bend at the base of a sink?

[kujawski]

because the water from the sink pushes it out

[pagey]

beautifully concise

[woody6]

that cant be entirely true. I realise the running water pushes the current water that is laying in the u-bend but....the water doesnt build up in the pipe directly under the sink, it somehow produces a pressure, shifting the settled water almost straight away.

[smart1984]

a certain amount of water stays in the bend creating a seal from the smells of the drain

[sidley]

The air that is in the pipe is compressed by the body of water from the next " sink emptying" and begins to move the water in the u-bend before the water actually reaches it!

[newtron]

The water levels on both sides of the u-bend (we'll call them the inlet side, wihch comes from the sink above, and the outlet side, which goes over a hump and to the drain) are equal and at the level of top of the hump on the outlet side. As soon as the water level on the inlet side rises above that on the outlet side, water will begin to flow over the hump on the outlet side. The water doesn't necessarily biuld up, but the water level on the inlet side does have to be higher on one side of the u-bend for water to flow through it.

[kwicky]

Water has weight. When added to the existing water in the u bend the surplus is moved further along. Although usually an S bend if you watch the movement in the toilet when you flush the contents it will help understand the process..

[Essentially]

No matter how you figure this out, if you consider the 'U' shape of the bend, the water on the left will equate with the same level as the water on the right.

The short drop to the beginning of the u-bend creates enough downwarm pressure to force it over and out through the drainage pipe till it settles once again.

~F~