OT: Physics/hydraulics of water and barrel

O.K. I get it now. Thanks, I was having trouble with that. The "column" is just a term for vertical distance, not shape. Makes mo-betta sense now! A column, to me as an arteest, is a tall thin object -sometimes convoluted in shape- which supports something. Not the same. Someone, Ed I think, had stated that before, volume didn't matter. I had to go back through the posts and reread them carefully, cause I wasn't understanding, you helped with the big picture. Well, I lost the stoopid argument, but I learned and will humbly accept my berating and move forward. Thanks again.

Shouldn't it be the area of whatever piston, diaphram, or whatever you're moving the water with, in the pump? The hose is just a weirdly shaped part of the reservior you're pumping water into.

--Goedjn

I had to read carefully too, but remembered the column is the smallest part all the way along, finally....

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's

I'm with you on this one - The barrel has a lager cross-section than the hose. Much like the pistons in a kiddie-toy-simple two-ram hydraulic system - Big piston pushes on fluid, sending it throrugh the lines to wherever the work needs to be done, where it presses against a smaller piston. Thethe smaller piston can be seeing *RIDICULOUSLY HUGE* amounts of pressure from a very light pressure being applied to the larger piston (The multiplication of force effect that comes from the larger piston displacing more fluid)

My take on this is that filling from the top would put take less effort from the pump - Rather than needing to fight both its own "head" (The size of the tube multiplied by the height it's climbing, if I remember rightly) AND the "head" in the barrel, the pump only has to push against it's own head until it's above the highest point of the barrel, where gravity takes over and delivers it the rest of the way.

Pumping to the bottom of the barrel means a steadily increasing head in the barrel as the barrel gets fuller. To go with the head developed in the fill hose. The pump has to overcome that "total head" to get anything more into the barrel.

How to test this theory: Put a pressure gauge at the lowest point of the system after the pump - right at the pump outlet would be ideal. Now fill the hose with water (You'll probably have to block the pump's intake to get any reading at all), and raise it into posiiton to fill from the top. What's the gauge say?

Now hook the hose to the bottom bung, make sure it's full of water, then pump until the top barrel is full. Shut down the pump and block the intake as before, and read the gauge. What's it say now?

My nickel says that the "from the bottom" setup is going to show a higher PSI than the setup to fill from the top.

"volume" has nothing to do with pressure. 'Only' the 'vertical height' (static head) is what requires the pressure; or, in another way.... each 2.31 feet (in the vertical direction) of water is equal to 1 psi. So, if the total height of pumping (includes the height of water in the barrel) is 23.1 ft. it will take 10 psi to 'push' it that far up

If you slowly submerge a pressure gauge into a large container of water, the gage will read 1 psi at 2.31 ft. submergence, 5 psi @ 11.6 feet, 100 psi @ 231 ft. ..... and it doesnt matter if the container is a vertical soda straw or the Atlantic Ocean. ;-)

The formula for the amount of pressure coming out of the bottom or top hole is:

Each foot of height provides about 0.43 PSI (pounds per square inch) of pressure.

The size or diameter of the tank does not matter. The pressure comes from the height of the water column. The pressure for any given height difference (from top tank to bottom tank) would be the same with any size tank. A million gallon water tank 10 feet off the ground will have the same water pressure draining as a 10 gallon tank, 10 feet off the ground.

Tom

via Encryption =----

If, and only if, the tanks are of the same height. If the million gallon tank is taller there will be more pressure.

Ignore the confusing input. ;-)

There isn't 100 PSI at the bottom of the barrel -- unless the barrel is something like 225 feet tall.

You'll get a little under half a PSI for every foot of height -- that is, the vertical distance between the pump and the top of the water. If you dangle the hose over the top of the barrel, the top of the water for these purposes is the top of the hose. If you actually run the hose over the lip, and down to the bottom of the barrel, the top of the water is the level of the water in the barrel -- once you have filled the hose with water. The principle is the same as a siphon.

So, fill the barrel wherever you want. It won't make a difference. I would fill it from the top bung so that it won't come out when you turn off the pump.

Ray Drouillard

Nonsense.

The pressure at the bottom of the tank depends on the height of the column of water in the tank.

The pressure required to pump water up to the elevated tank depends on the height above _ground_ to which it is being pumped.

In the situation described (a 55-gal drum elevated some eight feet above the ground) it is necessarily the case that the height of the water column in the drum is *much* less than the height of the drum above ground, and any pump that develops enough pressure to lift water eight feet necessarily develops more than enough pressure to overcome that exerted by the water already in the tank.

The only thing that matters is the *height* of the column. Sure, the water in the barrel weighs a whole bunch. Most of that weight is supported by the bottom of the barrel, though.

Ray Drouillard

GREATLY

If you submerge yourself a foot under water in Lake Superior, you had better be related to the polar bear. ;-)

Ray Drouillard

I figured it out thanks. I forgot about the smallest part of the column being the pressure regulator in a static stack.

Mike

mabar wrote:

Well you know, everyone else has explained why I was wrong, but you are wrong here with that snip quote.

That is 'not' nonsense. If there is 100 psi in the line and the pump can only pump 50, it will flow backward.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's

I pump juice through hozes all day long. Do not forget the diameter of the hoze - the bigger it is the faster you can pump. Friction in pipes is a real and very well understood phenomenon. So, if you can have a bigger hoze going to the top bung then you are better off doing thing that way.

I strongly advise filling from the top for this reason: If the discharge is above the water and the pump guits or the hoze pops off then you only lose one hoze volume of water. If you are filling from the bottom you risk losing the whole barrel of water. If you make and break fittings pretty soon they leak. Therefore if you have one line for discharge that is made up properly and never monkeyed with and you fill from a hoze going in the top you have Murphy insurance.

Jeepers proclaimed:

Tighten all bungs. Drop a round or two from a hand loaded big bore belted magnum thru it. Watch barrel disintegrate.

As you pump water up to the bottom, you'll be pumping water up thru N feet of gravity. You'll also be pumping it against the extra weight of water in the barrel, presuming that you left both top holes open so there is no increase in atmospheric pressure in the barrel. So the amount of pressure will be the water column of N feet plus the height of the water in the barrel.

When you pump water in thru the top, you'll be pumping water up thru "N+B" feet of gravity where "B" will be the extra height needed in order to run the hose up to the top of the barrel. This will always be higher than pumping up thru the bottom, so the water column will weigh more.

Heck make it really tricky and try to suck a column of water up a height of more than 21 feet at roughly sea level... less in the mountains.

>

Mike Romain proclaimed:

Exactly the same as if the hose were exactly the height of the water inside of the barrel longer. And always less than the height to the top of the barrel, which will always have a longer water column to pump water against.

Less likely to do so than if attempting to pump the water up to a height high enough to clear the top of the barrel.

All that matters is the pure height of the water column as can easily be measured or demonstrated by the artesian effect.

Jeepers proclaimed:

Nope. Height matters, width doesn't. Presuming the top has been vented to the atmosphere.

snipped-for-privacy@uri.edu proclaimed:

Nope. That only matters if you want to calculate how many linear feet of water moving up the hose it will take to make the depth inside the barrel rise by one inch.

Don Bruder proclaimed:

Except that this is totally irrelevant. Only if you are working where you put pressure on the water in the barrel...say by forgetting to open the top vent.