Draing a tank ?

[SS MAYFLOAT]

Okay here goes a weird question.

If you had a two tanks that was six feet off the floor of the same size full of water. The only difference was that one had a length of hose on the drain that went to the floor and the other didn't. Which tank would empty first if both started to drain at the same time?

BTW the drain hose would be the same size of the outlet of the tank. No reduction....

 

[robert graham]

Re: Draing a tank ?

The hose one would drain slower because the hose would slow down the flow rate....hope this ain't a trick question!

 

[SS MAYFLOAT]

Re: Draing a tank ?

The hose one would drain slower because the hose would slow down the flow rate....hope this ain't a trick question!

That is what I would think, but is it not possible that with the weight of the water in the hose being pulled down by gravity create a syphon effect actually causing it to drain faster?

Where is Mythbusters?

 

[Bob_VT]

Re: Draing a tank ?

Without adequate venting the one with the hose would take way longer and may even stop since air has to fill the void left by the water (unless it is a bladder). A siphon is just a drain with the same water pressure behind it.

Okay Mayfloat watcha making?????

 

[SS MAYFLOAT]

Re: Draing a tank ?

Okay Bob, lets say the tanks don't have any tops to them and there are no trees around for leaves to clog the drains

Not making anything. Just something today at work I discovered on an ice machine. I'll expain a bit more later on if others chime in for their opinion.

 

[tdrudd87]

Re: Draing a tank ?

I'm a little rusty on my fluid mechanics, but i could see how a tube of suffecient diameter could provide a more laminar flow rather than a simple hole. Probably depends on what size of hole/tube it is, even when they are the same between tanks.

So which is it?

Terry

 

[CN Spots]

Re: Draing a tank ?

I'll go w/the hosed one. Whenever I drain my 45 gal fish tank I use a garden hose running out of the house and down the driveway... the water usually shoots out of the hose.

My theory as to why is the same as yours. Gravity, suction, blah, blah, blah.

 

[SS MAYFLOAT]

Re: Draing a tank ?

The answer is the one with the hose.

Yesterday I finished testing out a rebuilt commercial ice machine. I had no hose attached to the drain. As the refill cycle was going on, the water would overflow the tank. Today, I put on the hose and now it does not overflow.

 

[83mulligan]

Re: Draing a tank ?

The answer is the one with the hose.

Yesterday I finished testing out a rebuilt commercial ice machine. I had no hose attached to the drain. As the refill cycle was going on, the water would overflow the tank. Today, I put on the hose and now it does not overflow.

that shouldn't be the case. you would have friction reducing velocity in the hose.

 

[PiratePast40]

Re: Draing a tank ?

With the help of gravity, the hose should also be drawing a vacuum. Sort of the way a toilet works, gravity is only half of the force, vacuum draws most of the solids through with greater force.

At least that's what they said on the discovery channel last night :redface:.

 

[jlinder]

Re: Draing a tank ?

Way back when I had a water bed. On occasion we would have to drain the bed and later refill it.

We tried draining the bed with a hose that went to the shower, about 2-3 ft vertical difference. Took a long time.

Added more hose, dropped the hose out the window to the ground 2 stories below. About 20 feet (we lived on a hill and the hose reached the ground at the garage door). Much much faster.

Now both had a hose, but the one to the ground was longer.

Does that help?

 

[rbh]

Re: Draing a tank ?

NOT a Hijack, but what about syphon and max 39 feet??????
why does this come to mind.
is there a rule I am forgeting about???

 

[jimr]

Re: Draing a tank ?

39' is for drafting water if I remember my old pump operators class from many many moons ago

 

[rbh]

Re: Draing a tank ?

39' is for drafting water if I remember my old pump operators class from many many moons ago

OK , Drafting???, I am lost now

 

[tdrudd87]

Re: Draing a tank ?

that shouldn't be the case. you would have friction reducing velocity in the hose.

There is a balance between friction at the hose wall, and turbulence at the entry to a tank. Adding a properly designed tube spout will increase the rate a tank drains by smoothing the flow before the inlet.

I suspect this is what happened here.
Terry

 

[j_martin]

Re: Draing a tank ?

OK , Drafting???, I am lost now

When you draw a vacuum on a pipe that goes downward into water, air pressure forces the water up the pipe, hopefully to the pump.

The maximum column of water that normal air pressure will support is 39 feet.

If you pound down a sand point 50 feet to water, you won't be able to pump it out. I've actually seen people do that.

A deep well pump is either submersible, where the pump is in the water, or a jet pump that has a water jet and venturi in the water that puts pressure behind the column of water, lifting it higher. A considerable portion of the pumped water is returned at pressure to the jet.

hope it helps
John

 

[rbh]

Re: Draing a tank ?

Thanks John-
I was trying to remember why I was told they only made the walls of a holding pit 39 feet, and that certainly makes sense now.

 

[45Auto]

Re: Draing a tank ?

Actually, the number you're looking for is about 34' feet at sea level.

A column of water 2.31 feet high is equivalent to 1 pound per square inch (PSI) of pressure. Using 14.7 PSI for atmospheric pressure, then a pump that can pull a perfect vacuum would pull a column of water 14.7 x 2.31 = 33.95' high.

If you're a mile high in Denver, Colorado, where the air pressure is only 12.1 PSI, then you can only pull a column of water 12.1 x 2.31 = 27.95' high.