Sciencey odd question just occured in my daily musings...

[WaterTight]

Is pressure less, by some infinitesimally small amount, at the end of a pipe run, say at a tap, than at the beginning, say at the internal stopcock? Because the pressure available to push water out of the stop-cock is less than the pressure available to push the water out of the tap, because it was finite to begin with so the further away you get from the source of pressure and the greater the amount of water said pressure is trying to shift the less the effect of the pressure and so the less of the residual pressure that is left....?

And if it is - if you ran a pipe, from the stopcock, in a straight line, level for a, for argument's sake, potentially inexhaustible distance in miles - if there was sufficient water to fill this pipe all the way up until the point of exit but the pressure as the stopcock was just normal mains pressure, would you reach a point where nothing would come out the other end? Because the pressure wasn't great enough to move the water through the pipe? And is there a calculation to work out what this would be? It's much easier to think about water being pumped upwards when gravity is fighting you and the limitations there.. Just wondering if it's was in a straight line..

If this effect does exist and doesn't actually require very long distances before it can cause problems I guess it would be part of the calculations used for commercial plumbing. I only thought because there's another thread about running a pipe for an outside tap for 25metres. Made me think how long you'd have to run a pipe on mains before it was too long to work.

 

[ecowarm]

If there is no friction then there are no friction losses so the pressure remains constant

But he said no pump so how do you maintain said pressure in a level pipe how ever long?

 

[tamz]

Never noticed that bit:shame:

So, if i've got this right, we have a level pipe of infinite length with no applied pressure but as it is on earth, it is subjected to gravity.
Cut the end off the pipe and it will empty...............eventually.

 

[ecowarm]

Glad we didn't get into the electric losses that some one posted as well

 

[mickie]

if your talking about a pipe in outer space their wouldnt be any pressure and if you opened each end water wouldnt flow anywhere, it would stay still, untill someone moved it, using a force of pressure or gravity moved the water down..

 

[tamz]

Ah, but we are now back on earth (post 59) so subject to the usual forces :lol:

 

[mickie]

water run level for a long distance, say 1000 miles, i dont think would work, due to the moons pull on water, just look at the sea, it goes in and out, but i think it would work if the water was raised up from the ground, as that would increase its pressure..its pressure would never come down over the 1000miles, but its flow rate would due to friction so you'd have to fit the currect sized pipe to cater for its run

if size didnt matter, the water board would be using 15mm pipe under our roads to feed everyones home.. i dont know the math in sizing water mains though

 

[tamz]

So the pipe might have a high and low tide:speechless:

 

[mickie]

well if run totally level without any real pressure, bar its own pressure due to its own weight on the earths gravitational pull and say we had no moon, if you opened each end water would flow out slowly, but factoring it the moons pull on water, depending on where the moon was water would naturally want to follow the moons path, would it not ?

dont really understand the question, who'd want to fit a pipe without increasing its pressure

 

[tamz]

I suppose as long as the money was right , wgaf. Just keep laying pipe. No pressure as it is an infinate job!

I'm out:sleep1:

 

[fuzzy]

if your talking about a pipe in outer space their wouldnt be any pressure and if you opened each end water wouldnt flow anywhere, it would stay still, untill someone moved it, using a force of pressure or gravity moved the water down..

there is gravity on the moon, its just reduced 1.6n/s/s instead of 9.8n/s/s. So i pipe on the moon 25 miles long would take 1/6 of the time to empty. However, if it were pumped and pumped upwaards the restriction due to gravity would be less, its all pros and cons lads

 

[fuzzy]

Ah, but we are now back on earth (post 59) so subject to the usual forces :lol:

stop trying to simplify things tamz

 

[fuzzy]

NO there is no gravity in space therefore the water would be weightless

are you just an earth plumber? not got your 'moon' ticket? Ask at your local centre, when your doing heat pumps

 

[WaterTight]

Well I'm still a bit confused but I think the answer is too many other factors would get in the way of the experiment.

I suppose what I want to imagine is say you are on this magical world for this experiment - you have this level stretch of 1000 miles of pipe, which is not effected by friction, is neither subject to the effects of gravity nor the effects of no gravity, where the only thing being tested, somehow - magically - is whether the mass of this water itself can hold back pressure when applied.

So this pipe would be full of water but not pressurised. Just at the pressure it normally would be at. At the far end is a tap which will be opened shortly. Then, 1000 miles back the other away is a valve which is closed. On the other side of the valve is more pipe, containing water which is pressurised to 1.5 bar. If you open the valve the pressurised water comes into contact with the non-pressurised water, sitting there for it's 1000 mile stretch - if you then open the tap 1000 miles away does water come out or not?

 

[WaterTight]

And if this has now been answered already and I'm just too thick to get it and everyone else does I apologise and will stop bothering everyone :43:

 

[unguided1]

not answerd yet dont forget if a pipe is a 1000 miles long layin on a planet, the natural curvature of the planet will allow air in when you open the pipe allowing the water to pour out

 

[fuzzy]

Well I'm still a bit confused but I think the answer is too many other factors would get in the way of the experiment.

I suppose what I want to imagine is say you are on this magical world for this experiment - you have this level stretch of 1000 miles of pipe, which is not effected by friction, is neither subject to the effects of gravity nor the effects of no gravity, where the only thing being tested, somehow - magically - is whether the mass of this water itself can hold back pressure when applied.

So this pipe would be full of water but not pressurised. Just at the pressure it normally would be at. At the far end is a tap which will be opened shortly. Then, 1000 miles back the other away is a valve which is closed. On the other side of the valve is more pipe, containing water which is pressurised to 1.5 bar. If you open the valve the pressurised water comes into contact with the non-pressurised water, sitting there for it's 1000 mile stretch - if you then open the tap 1000 miles away does water come out or not?

no, the weight of water would be too much for 1.5 bar to overcome it

 

[fuzzy]

not answerd yet dont forget if a pipe is a 1000 miles long layin on a planet, the natural curvature of the planet will allow air in when you open the pipe allowing the water to pour out

arrrhhhhh

ok, lets also pretend the earth is flat

 

[WaterTight]

no, the weight of water would be too much for 1.5 bar to overcome it

Soooo.....what we want to know is, how long would a piece of 15mm copper full of water need to be when subjected to 1.5 bar before water couldn't come out of the other end but ONLY because the weight of the water in said pipe would be too great for it to be pushed out by available pressure?

I've done the calculations and its 643.274653 miles. No need to check, 100% accurate, absolutely.

 

[GQuigley67]

I'm sorry guys but water would boil in space, thats what happens to you in space the water inside yer body boils !

ohh and did you know that at the deepest part of the ocean the mariana trench(6.85miles) the pressure is over 8 tons per square inch ?? lol

 

[Mrs Tara Plumbi]

Only just read this gem of a thread - physics, maths and astonomy - my all time favourite subjects, appart from a few not taught in my catholic school!

In deep space the temperature is just 3 degrees warmer than absolute 0 so approx -270 C
So the water will definitely freeze.
Not sure what happens to copper or plastic at these temperatures.

As said earlier if there were no forces such as gravity or friction then ANY body set in motion will continue to move in a staight line at a constant speed, as in a vacuum or deep space.
In side the theoretical frictionless pipe the water release at mains pressure will continue to move at the same speed BUT i think you question is that this water then meets an obstacle which is the still water sitting in the pipe.
So you need enough pressure to move the still water. Sorry if i am repeating what was said..

I'm not sure the moon will have any effect on the water in the miles of pipe. Because I think the moon - tide thing is to do with a big body of water like a giant swimming pool. Along this theoretical pipe there is always a small amount of water in any one place.

 

[GQuigley67]

it actually boils before it freezes then turns into ice droplets

 

[Mrs Tara Plumbi]

While you were writing I was checking my facts!
of course I forgot that water boilers at lower temperature when pressure drops.
I don't know what the pressure is in deep space?

But I was thinking of comets and rocks like pluto being largely frozen ice. But of course they have mass and pressumably higher pressure than deep space. Makes you think...

 

[GQuigley67]

[DLMURL="http://scienceblogs.com/startswithabang/2009/06/water_in_space_what_happens.php"]Water in Space: What Happens? : Starts With A Bang[/DLMURL]

interesting page

 

[GQuigley67]

sorry correction, it boils faster than freezing so in effect it is freezing but turning into a gas at the same time lol mad

 

[diamondgas]

do you have 25 mile of copper on the van?

diamondgas wants to do it in speedfit, but i think thats cheating, in fact ive decided hes a big wuss now and i o longer consider him a real plumber, psss, dont tell him

how about doing it in iron? ive got some hand dies

I have'n got a finger big enough for iron fuzzy and i am a wuss .... Part time plumber full time gas engineer :rofl: Haven't got a clue when in comes to anything waste related and have never fancied messing with toilets, baths and the like... leave that to the proffesionals lol ...

 

[Mrs Tara Plumbi]

And this covers a lot of useful stuff but doesn't quite anwswer the question
Domestic water-supply system - theory - JohnHearfield.com

this chap does know Renolds

 

[GQuigley67]

And this covers a lot of useful stuff but doesn't quite anwswer the question
Domestic water-supply system - theory - JohnHearfield.com

this chap does know Renolds

thats 1st year stuff lol

 

[fuzzy]

Soooo.....what we want to know is, how long would a piece of 15mm copper full of water need to be when subjected to 1.5 bar before water couldn't come out of the other end but ONLY because the weight of the water in said pipe would be too great for it to be pushed out by available pressure?

I've done the calculations and its 643.274653 miles. No need to check, 100% accurate, absolutely.

so your saying we are good for the first 642 miles?

 

[fuzzy]

I have'n got a finger big enough for iron fuzzy and i am a wuss .... Part time plumber full time gas engineer :rofl: Haven't got a clue when in comes to anything waste related and have never fancied messing with toilets, baths and the like... leave that to the proffesionals lol ...

its all very clear now, so how far would gas travel if subjected to a force of 1.5bar in a 15mm copper tube?

 

[diamondgas]

its all very clear now, so how far would gas travel if subjected to a force of 1.5bar in a 15mm copper tube?

Up hill, down or on the level? I'd be gettn' the meter gov checked if I was getting that sort of presure ... imagine the cooker flame!!! lol