Pressure, head, and pumping into tanks

[@jmohammedtt]

I think you explanations are great for young and aspiring engineers.

[@ProcesswithPat]

Can’t tell you how pleased I am to hear that!

[@jmohammedtt]

@@ProcesswithPat I've been a process engineer for ~16 years. Whilst I understand all the concepts you explain, I can see how learning these at an earlier stage in my career would have been invaluable. Keep up the good work.

[@baselsteel4976]

@@ProcesswithPat It's a great video but it can be even better :) In terms of pressure (& neglecting friction losses as you correctly indicated) they are equivalent.. but let me add an important note to your very helpful video: There is a major difference when the pump stops... the water will come back in cases B & C... this means that the pump will turn in the opposite direction which will prevent you from running it again & possibly damage mechanical seals (if used) & other critical pump components... Neglecting the extra cost, You can put an NRV (non-return valve) but what if it passes water? Or requires maintenance? Yes you can put an isolation valve... but this is not the correct way... you should select the inherently stable system; that is case A (Unless the system is small, You will have to put both the mentioned valves in case anything happens in the middle! But you will not have to worry about the water in the tank only the water in the line) *having taught students for a long time I learned that I have to mention such significant points or at least "stress" on the fact that the comparison is strictly in terms of a specific aspect (in this case; pressure/head only) & in reality many other aspects have to be considered... this is because many would have the tendency to "over simplify" the problem, just repeat that everything is equivalent & cause a disaster! * again I know it is not directly related to the question but yet I feel it is important to mention such issues, have a good day

[@simonmasters3295]

Nicely articulated, one could say "case study in over simplification" by focusing on pressure alone. In my own 13,000 litre heat in water solar capture system, the fill line is small diameter Flexi, providing a low continuous rate of circulation of warmed or chilled water through any one of 13 containers with filling at any level adjustable without valves by manually physically relocating both the flow and return lines without disconnection of a pond pump directly attached at the inlet and a solar panel providing flow in proportion to incident heat. Any the high pressure generated and friction in long lines is accepted as free heat making the inefficiency of overpressure into a benefit. A loss into a gain.

[@r1273m]

@jmohammedtt ...and for really old guys like me that have forgotten so much of this kind of thing!

[@dale116dot7]

One advantage is that filling from the top instead of the bottom happens if the pump blows up. If you fill from the bottom, the tank will empty through the shrapnel that used to be the pump housing and onto the floor. If the contents of the tank is water, it is inconvenient. If it is sewage or chocolate, you have a heck of a mess to deal with.

[@justanotheryoutube]

True, but one advantage of filling from the bottom is there is less head pressure during the entire filling processes, only when the tank is full is the pressure the same as filling it from the top.

[@actionjksn]

That potential problem could be prevented by putting a check valve in the line right after the pump.

[@dale116dot7]

@@actionjksn It can be, though there is a pressure drop across that valve too, although an active valve (pneumatic for example) could reduce that to almost nothing. Like anything in engineering there are multiple solutions.

[@rupe53]

@@justanotheryoutube ... while that makes perfect sense, the main reason to fill from the top has to do with fluid dynamics where an open ended pipe just has less restriction and an even flow rate throughout the fill process. BTW, the open end also acts as a siphon breaker in the event of needing pump service. IOW, you don't have to empty the tank.

[@trevorliu735]

@justanotheryoutube and @rupe53 The other reason to fill from the top of the tank is that the Pump is pumping against a known and constant head. If pumping into the base of the tank and the tank having varying fluid levels, the Pump is not pumping against a constant value but a value which varys with the level. Pumps have an head curve where there typically is a narrow range of optimal conditions. Pumping to the top of the tank removes one of the variables in the design.

[@baselsteel4976]

In terms of pressure (& neglecting friction losses) they are equivalent.. but let me add an important note to your very helpful video: There is a major difference when the pump stops... the water will come back in cases B & C... this means that the pump will turn in the opposite direction which will prevent you from running it again & possibly damage mechanical seals (if used) & other critical pump components... Neglecting the extra cost, You can put an NRV (non-return valve) but what if it passes water? Or requires maintenance? Yes you can put an isolation valve... but this is not the correct way... you should select the inherently stable system; that is case A (Unless the system is small, You will have to put both the mentioned valves in case anything happens in the middle! But you will not have to worry about the water in the tank only the water in the line) *having taught students for a long time I learned that I have to mention such significant points or at least "stress" on the fact that the comparison is strictly in terms of a specific aspect (in this case; pressure/head only) & in reality many other aspects have to be considered... this is because many would have the tendency to "over simplify" the problem, just repeat that everything is equivalent & cause a disaster! * again I know it is not directly related to the question but yet I feel it is important to mention such issues, have a good day

[@JaakJacobus]

But in case A there's always a maximum counter pressure even if the tank only half full. This will reduce the flow quantity.

[@gr8dvd]

"not directly related to the question" Wrong, I suspect an extreme case of modesty 😀 But seriously, some mention of application is both helpful in sustaining interest AND understanding the theory.

[@baselsteel4976]

@@gr8dvd Thanks Indeed, Slowly Injecting things from an application perspective will always help fresh engineers/students (we can not go full throttle on details since it will deviate us from the topic at hand, but "some mention of application"👌 is much better than the "bone dry Theory" methodology)

[@baselsteel4976]

@@JaakJacobus *I did not understand what you mean by "counter pressure" *In Case A, the tank is filled from the top not the bottom *If we are talking about the same case, do you mean the friction losses/head losses (which translate to pressure losses) due to the length of the pipe & fittings? In cases B & C, The entrance losses are very large especially if it is directly from under the tank as shown (rather than from the lower level but from the side of the tank)... this is due to the induced turbulence in the tank at the entrance * even if the losses are larger in case A (which is unlikely), the huge disadvantages of the other cases (mentioned in my previous comment) force us to use case A in practice * the drain of the system should be at a low level & on the side of the tank... not the entrance This is Another reason why we don't put the entrance below... since all debris, rubbish, sand, gravel...etc tend to go down such openings and choke the pipe (causing interruptions in operation & resulting in expensive repairs...) * extra: Some times, especially in large size pipes we use "long neck" elbows to reduce the friction losses caused by traditional elbows (due the abrupt change in flow direction) When filling the tank, in small systems we usually use "floats" to signal the pump/s to stop once the water reaches a certain level (which should be below the entrance level) In bigger scale systems we usually use other means such as ultra-sonic sensors to stop the pumps... Hope this helps :)

[@baselsteel4976]

Another reason why we don't put the entrance below... since all debris, rubbish, sand, gravel...etc tend to go down such openings and choke the pipe (causing interruptions in operation & resulting in expensive repairs...)

[@rolandhanbury5641]

One aspect that nobody seems to have mentioned is that a key reason to prefer bottom filling in many applications (e.g. rural water tanks) is that you can use the same pipe for both inlet and outlet for much of its length, thereby nearly halving the quantity and cost of the pipe needed. In the case of a tank on the top of a hill that is distant from both the dwelling and the water supply that can be quite significant.

[@legro19]

It reduce the quantity of gas in the liquid too, wich greatly reduce cavitation in the pump. This why even if you pump in the top of the tank often the pipe continu in the tank to the bottom. Essential in case of high pressure pumping.

[@theeraphatsunthornwit6266]

my tank fill at the top, or otherwise the water will run back to the source when source has no water....... or check valve is needed

[@legro19]

@@theeraphatsunthornwit6266 You have the most reliable check valve possible.

[@Colorado_Native]

True. When refueling aircraft they pump from the bottom of the wing for a couple of reasons. They don't have to pump a greater amount of fuel up and over the wing. Also, it's safer than having to drag the hoses over the wing and even possibly damaging the wing.

[@pw6048]

Not only that, ik you fill from the top, like in the example as seen in the video, you ALWAYS have to rise the water 3 meters, and the pump always has to use maximum presure ( and energie) to do that. when filling an empty tank from the bottom, it just costs a lot les energie to do it from the bottom. than from a fixed heigth at the top.

[@GerhardAEUhlhorn]

The pressure loss cannot be neglected! Example: Pipe DN40, 10 m length Flow rate: 320 l/min Flow velocity: 4,5 m/s Pressure loss: 0.5 bar With solution B and C you need less pressure.

[@boilermaker1337]

Also, exit losses will be different and "A" has one more elbow. The analysis in the video is quasi-static. There's nothing wrong with that, but it should be mentioned.

[@whatevernamegoeshere3644]

Side note: It should be calculated for 3 meters, it was 10 feet

[@Holzner1991]

No tank is always full. A pumps always 3m. B and C don't have to pump the missing height.

[@CatNolara]

What I like about A is that if you turn off the pump, the fluid stays in the tank and doesn't flow back (only the portion in the pipe)

[@GerhardAEUhlhorn]

@@CatNolara Yes, this is true.

[@nikeelim7878]

just found your channel and it’s so useful and relevant to me atm as a third year chem engg student!! i love how you can break down problems into ways we can easily understand thank you

[@ProcesswithPat]

That’s really kind. Welcome and I hope you find more that is useful!

[@WillKemp]

This clearly true, and I've known it for a long time, but I had never thought about the difference between pumping water up a pipe into the top of the tank (which is the way it's usually done) and pumping it into the bottom. Pumping it to the top requires more energy because you're always pumping at a higher pressure than is really necessary (most obviously when the tank is empty), but pumping into the bottom only uses the amount of energy to pump against the head of the water in the tank.

[@cyrilvankeirsbelk7299]

But pumping to the top of the tank results in a constant pressure, allowing you to design a pump for that pressure and not variable pressures. You also don't have to worry about a back-flow valve, one additional fail point on a system.

[@_Coffee4Closers]

This was a good explanation for the average layman. I am glad you mentioned you are ignoring frictional losses as I assumed by the question that "pumping" is a part of this equation. So I immediately assumed that Option C is the lowest loss, Option B is the second lowest loss, and Option A is the highest loss. All options pump against the same static head, but option A has the highest frictional loss, and Option B has a higher Discharge coefficient than Option C due to the 90 degree angle at the discharge point. Option C has a less that 90 degree discharge angle and therefore less loss due to the lower discharge coefficient. This takes me WAY back to my Engineering school days.

[@Coen80]

When I pump horizontal, how do I know how long my pipe can be? I want to pump water 100 - 200m through the garden (downslope) in pipes that maintain some pressure for the sprinklers. I understand this height (Hm) now a bit, bit i haven't figured out how to calculate how strong my pump needs to be to keep pressure for 100 metres of pipe. Can anyone explain?

[@zerocanvas6163]

the difference is not in the final state, but in the transitory one. in 1 the tank will be filling at a constant rate but in 2 and 3 there will be a variation in the rate of filling because as it fills the pressure will increase as the water column rises. there are other differences, like If there is a leak in the filling pipe and the filling is from above, it will only leak while it is being filled, if it is from below it will always leak liquid.

[@zerocanvas6163]

other thing i hear people saying is that in 1 you will save pumping energy by filling from the bottom, because you won't be working against the full tank head when the tank isn't full, whereas if you fill from above you will be against the full head all the time. But in reality that does not work that way because the pump will work as its curve says .initially you will have less H and more Flow and the eficiency will be different.

[@ronblack7870]

@@zerocanvas6163 you assume a centrifical pump. why do that.? much liquid pumped into tanks is actually pumped with lobe pumps where the flow will almost not change with head but power will.

[@zerocanvas6163]

@@ronblack7870 At the place where I work (olive oil processing plant), centrifugal pumps are used for tank filling because the filling flow rate is the most important factor (it must be fast). Positive displacement pumps (gear pumps) are used to transfer the oil from the storage tank to the bottling line.

[@actionjksn]

A simple check valve will prevent it from leaking if there's a failure. All sump pumps have this, although they have it to keep the water from the vertical pipe from flowing back in to the sump, but it would still work to prevent a week in the event of a failure.

[@bipl8989]

There is no difference in the transitory state of pressure. In #1, the same pressure variation will occur when filling the riser as when bottom filling the tanks. The difference is that the riser will be filled quickly and, once filled, the pressure to fill the tank remains constant. Whereas bottom filling, the pressure varies over the entire time required to fill the tanks, from start to finish.

[@pwrofmusic]

Great explanation. Ive worked on oil taker ships and had to pump oil into tanks a mile away and on high hills where there was alot in of head.

[@HostileRespite]

Fantastic video. Simple explanation and graphics to help the viewer grasp the point. Thank you!

[@ArgondtheGrey]

Technically would be slightly easier to pump to the bottom because there is a shorter pipe and therefore less friction loss. In a 1.5 inch pipe we would add one foot of head for every ten feet of hose or pipe when calculating output. The extra 90 degree elbow would also contribute to reduced flow. I was a professional pond installer, we needed to know how large a pump would be required for the waterfall. The pumps specify output at the pump, then you add up height above waterline and the lenght of the pipe to determine outflow at the top of the waterfall.

[@vincentrobinette1507]

When filling an empty vessel, it's more efficient to pump into the bottom, than the pipe at the top. That's because, the head pressure doesn't reach it's maximum until full. With the pipe filling from the top, it requires full head pressure for the entire volume of the tank, meaning more energy was used to fill the tank to the full mark.

[@marciochao4849]

Why i didn't found this channel earlier! You're awesome pat! Thanks for sharing this knowledge

[@moamenkamal]

Excellent explanation and makes sense to visualize it. Please Keep going and posting more videos. Thanks

[@deansawich6250]

Great explanation. The difference comes in when one has to select a suitable pump. Then the other aspects have to be taken into account.

[@michaeldoherty7434]

I’m glad you mentioned the minor differences in friction as that’s the first thing that came to mind.

[@yellingintothewind]

Yes, and note that this only considers the hydrostatic case. To see that the hydrodynamic case can be different, consider the swimming-in-the-ocean example, but with an impending tidal wave. In water retention systems, this shows up as "water hammer", and is a major engineering challenge in some situations.

[@3in1Supadiverta]

Found this by accident, great video. I have trouble explaining this to many customers and even plumbers. One day I hope to make a video showing a retention tank scenario with varying water levels. 🤠

[@JohnWilliams-iw6oq]

You confirmed my thinking, I live in rural Australia and quite often transfer water. Thank you.

[@richardeltringham3090]

Another awesome and super interesting video! 😃

[@jeffmoreton2752]

Altered my perception it would actually use less energy to bottom fill as the head increases only as the tank fills and not the constant head determined by the height of the tank. Would only be significant in a really tall tank perhaps

[@rokoala2636]

It does use less for the reason you just said. The video was just explaining that only the head matters, not the total volume.

[@Jake-zc3fk]

Very well explained, thank you!

[@millionroots3102]

Thanks. Beautiful illustration.

[@harpo7226]

Thank you I learned something new today. You made that really simple to understand.👍

[@croxy57]

You are 100% correct, and because the example is dimensionless there’s no point arguing the effects of friction, velocity head etc.

[@oatkeroder]

That was a great explanation. Thanks.

[@oilman1758]

Always wondered about that. I would assume pipe on outside would be easier to pump. You explained it perfectly in simple terms so anyone can understand. TY

[@Moist_yet_Crispy]

Subscribed! Looking forward to more of your videos :)

[@nunyabitnezz2802]

Excellent info. Excellent explanation.

[@farmcat3198]

This was pretty interesting. Thanks!

[@TonySwitzerland]

Excellently explained!

[@mspeir]

I learned this two decades ago when I was really into the saltwater aquarium hobby. The bottom glass needs to be thick enough to withstand the total weight of the water and contents, however, the sides only need to be thick enough to withstand the static pressure of the water column. For my metrically challenged self, 1 PSI ≈ 27 inches of vertical water column.

[@mikep490]

Yes, roughly double the thickness of material is needed for the bottom compared to the sides for aquariums mounted on a stand that supports the bottom only by the rim. There's an exception. If an extra support band is added to the center of the bottom glass, that reduces stress and similar thickness can be used. In practice, if set on a solid level surface, thinner glass could be used since it'd now (mostly) be there simply to seal water in. That's one reason why huge aquariums (and bathtubs) are often set atop thinset (cement) for additional support.

[@bipl8989]

Not exactly. Weight equals pressure. Bottom carries pressure, which equals the weight. The reason the bottom is thicker is that the pressure is constant all across the bottom, whereas the force on the side is the average of the pressure at the bottom and at the top. Top is zero, so force on the side is roughly half of the force on the bottom.

[@mikep490]

@@bipl8989 Correct, but it's the unsupported dimensions that matter. Let's say you have a 30x60 bottom. If you add a center support, each half of the bottom is now a 30x30 distance, roughly half the weight. You see that in buildings, as in using posts, load bearing walls and foundation supports below floors.

[@gustavoespinoza7940]

Great answer! This should only apply if the diameter of the pipe is the same in each case And the number of bends in the pipe are the same. Otherwise you get a pressure drop

[@andrewbradfield5500]

Great stuff Pat 😆

[@dixon_est]

Easier to explain - pressure is a measurement of force per units of area (example: pounds per square inch). To find total force, pressure needs to be multiplied with the area of application.

[@allezvenga7617]

Thanks for your sharing

[@b4ph0m3tdk9]

So well explained!

[@ErikBongers]

I had seen the video you are referencing to, and because of that reason only, I was able to pick the correct answer. It still is extremely counter-intuitive though. The only way I can make it intuitive for me is not to think of pressure but of gravity. It only points down, straight down, even in a funnel. However, filling a thank from the bottom, probably suffers a bit from inertia and friction: the water that is already in the tank has to move away for the new water to enter. Imaging sand or grain. But I assume with water that's negligible.

[@matjazwalland903]

Thank you for the explanation! But I have two questions. 1. If the tanks were empty, would you notice a difference in pressure? 2. If we pump into the reservoirs a liquid with a higher density than the liquid in the reservoir? and an additional question, reservoirs have different internal pressures 1. it is below sea level, 2. it is at sea level, and 3. it is at an altitude of 3000 meters? In which reservoir would it be easier to pump liquid?

[@JB-qg2uc]

There is a surprising difference in the pressure loss from having a flat inlet vs conical inlet. This also applies in the case where the water is pumped to the top, due to the extra 90degree turn. Though the exact solution would depend on the radius of the 90degree piece and the radius of the pipe.

[@BCarli1395]

Thank for an interesting presentation.

[@ssu7653]

5:43 Perfectly show how these questions are very often designed to trick people. The top and bottom of water in A/B/C is not in line with eachother, of the background have a slightly tilted pattern. This makes your brain think there are different heights to each water colum, even when you know how the water pressure work

[@Lufe6301]

That is one reason why, in a Refinery fluid is pumped into (and out of) the bottom of a tank. Product levels vary in a tank so it takes less time to fill it from the bottom and less pipework.

[@thatcanadianwhitetrashguy]

Good Job Bud

[@krabkrabkrab]

This can also be explained from energy consideration. The energy needed to pump liquid in is force (F) times distance dx, which is (F/A)(A dx)=P dV. But we know the energy needed is (dm) gh. Equate the two to get P = (dm/dV) gh = density g h. This is independent of how the water gets into the tank.

[@bipl8989]

Less energy needed for bottom fill, since all fluid does not have to be lifted over the top of tank rim. Less energy is needed in bottom fill since the pressure (height of lift) is much less during the initial stages of filling.

[@TopGigaChad96]

Thanks for using the Metric system.

[@B30pt87]

Thank you!

[@murraymadness4674]

That was great. However that the small tube can transport water without having the tube full and thus have the full height of water pressure on it. For example a screw type setup. Now of course, it is a form of leverage where the rate of water filling is less. It would be like filling it a cup at a time using a pulley to pull up the cup and dump it.

[@mortensen117]

There is an even simpler way to see the identical-ness than the pool comparison: If you end up raising a "plate" of water the same height in all three cases, that is, end up "putting" the same volume of water at the top, then the increment of potential energy in all three cases are the same.

[@tomgreene7942]

When filling and using hazardous materials, the codes or standards usually require filling from the top, with a check valve and a vacuum relief valve. They don't want the tank emptying if the pipe springs a leak. A pump is also required to pump it out of the tank. A vacuum can be used to pump it out but only if the vacuum relief valve is electronic. Strangely though, while working at a oil terminal, they pumped and drain from the bottom, so they must have had an exemption written into the codes.

[@TheJarrodh]

Intuitively pumping through a pipe to the top of the reservoir is greater due to friction losses through the pipe, which you don't see if you pump directly to the bottom of the tank.

[@michaelwarren2391]

Yes, and he did mention that.

[@colbyscott9822]

The answer to the question is built into the unit PSI, ie. pounds per square inch, not pounds per cubic inch. The two dimensional unit implies that the pressure will only be applied on one plane, which functions as the boundary for the column of water above it.

[@AndrewCampbell-ut6jk]

Good explanation as many people don't get the concept at first.

[@andvil01]

As a brewer with 100 m3 15 m high tanks, the pressure of the water collumn is something to count on. Easy over 1 bar at the bottom.

[@albratgaming2348]

My Initial answer was B. The I watched the video and was happy that my answer was correct. This is because C and B are the same. A is actually slightly more pressure, because the lift is to above the column of water in the tank. But it is also nearly no difference.

[@redneckminer9164]

Nice video!

[@wayneyadams]

Fresh water is simple to remember, the pressure is about 0.43 psi per foot. For a quick and dirty approximation, 0.4 will work 2.50 What leads people astray is the fact that in a tank with vertical sides only the column of water directly over the pipe exerts pressure on the pipe. So a ten foot column of water exerts 4.3 psi at the bottom of the tank which is the same pressure it takes to pump the water to the top of the tank.

[@katynewt]

Good explanation. However, according to your drawing, the pressure in B and C should be almost the same, while the pressure in A should be lower because its water level is a bit lower than the ones in the other two.

[@PeterSedesse]

Pump or electrical failure are the reason to chose #1. However, in certain use cases #2 can save you money with pipe costs.

[@n8mail76]

I astounding how complicated physics is. I wonder if that has any deeper meaning than the obvious.

[@asandax6]

KZbin is now reading minds I've had this question on my mind but haven't searched for it and look at that it just recommended this video.

[@GemulChannel]

The reason i use A is because from my pump (submersible in the waterwell) to the water tower doesn't have any check valve. The pipe is always empty when not pumping. if I use B or C, the water inside the tank will flow back to the well. And i know well enough not to touch something that works so i keep it that way.

[@hughjanus3378]

Interesting question. The pressure that the pump has to supply at the same flow rates is greatest for A, less for B and the least for C. A has static pressure plus pressure loss to generate the flow. The pressure to generate the flow is from the friction in the wall of the pipe and the discharge pressure required to expel the water from the pipe. B has static pressure plus pressure loss to generate the flow…..which is less because there is less length of pipe experiencing the full flow and the velocity up the tank is negligible…PLUS the pressure required to force the water into the tank…..because the water has to flow into water residing in the tank…which requires pressure. C has all of B…..but…..the tapered entry into the tank will require less pressure than B….so the pump supplying C will read the lowest pressure while pumping. All three will read the same when not pumping if the water levels are the same. Q.E.D.

[@geoffreyworley5853]

Excellent

[@UpRealBug]

I dont see anyone realising, that when the tank is open, you only pump againts atmosferic pressure initially (with the bottom set up) and you only reach the 3 metres of pressure as you reach the end of filling. With the top set up you always need to reach 3 metres of pressure....so unless you cant risk your fluid spilling on the floor. the bottom feed is way better becuase it requires less work (electicity/money)

[@ruffnutz71]

In practice though , rarely do you want to pump into an already full tank So pumping into the bottom of a tank is more efficient right up until the point the tank is full. At which point you would need to stop pumping anyways. Pumping into the top of a tank is always at max pressure whilst pumping in from the bottom there is an energy saving right up to the point of a full tank and switching off the pump. When they are both at 3m its the same pressure. ( I am aware I am answering something that wasn't asked in the original question)

[@Stampalex]

Found you by accident -- great video - Have subscribed.

[@josebuenfil7559]

Gracias

[@marksherrill9337]

Interesting. I knew this is the reason a dam is able to hold a reservoir, but expected the cone shape to have more pressure.

[@dermatologymiami]

Thanks I get it now

[@ahmedhasabo6647]

Nice thanks

[@user-vs4by3zh9m]

Wow Thanks

[@ryleebrownfox]

Pumping water into tanks B and C is much better than into tank A. However, for potable water system, governing codes require the inlet pipe to be 100mm or more above the top level of the overflow pipe. This is to isolate the water supply from the stored water in case the tank is compromised.

[@wayneyadams]

Here is an interesting question from an old entrance exam for the US Navy nuclear power program. There are two sealed tanks connected at the bottom by a pump which has Pipes with valves on either side which can be closed to remove the pump. One tank is filled with water and the other is empty. How do you pump water from the sealed full tank to the sealed empty tank.

[@MrArray1967]

Interesting question and explanation. BUT. Filling tanks with pumps require less energy when pumped through the bottom than when pumped through a pipe connected to the top of the tank!

[@user-sm9hh9hz8j]

رائع ، أحسنت . 👏

[@davidgamble7180]

If you pump into the bottom of the tank it takes less energy because the column of water is always less than the full level.

[@yellingintothewind]

_Never more than_ the full level would be more accurate. In the diagrams, there is some distance from the top of the tank to the upper fill port. If the fluid exceeds this, then the heights become equal.

[@bipl8989]

Not true.

[@tomkarlsborn2384]

What about the energy used to fill the container from empty to full? The smallest amount of energy needed would be to fill B as the head increase is slowest. Next comes C and the worst case is A where the head is at a constant maximum. This would be a consideration if using battery power for instance.

[@tdcmachine]

In the conical tank diagram, shouldn't the pressure be shown as straight down in regard to water column and not perpendicular to the bottom of the tank as illustrated by the yellow arrows. However, there is outward pressure being exerted on all sides of the tank, so pressure in the tank might be indicated by perpendicular arrows.

[@jameschains]

Brilliant

[@davidn4125]

However, scenario A requires more overall energy to fill the tank than B or C. Think of slicing the tank into thin slices of water. In scenario A you are lifting every slice of water to the top edge of the tank while in scenarios B & C you are not.

[@rupe53]

you are correct, but fluid dynamics and fluid viscosity will also play a roll. In theory, an open ended pipe will have less resistance to flow, even though it will have the same head pressure at the same height. You also have the advantage of a siphon breaker in the event that something fails in the pump system.

[@ColinRichardson]

Pumping into the bottom of the tank only has the pressure of how much fluid is already in the tank, whereas pumping into the top always has maximum head.

[@savannahrei8674]

It seems like the pressure of the inlet pipe should have something to do with the result. For example, if you were pulling a vacuum at the outlet of the pipe dumping into the top of the tank, like you were sucking on a garden hose, once the water starts to flow, you don't need to pump anymore because of syphon action.

[@tyrranus_tyrranus]

A siphon works due to a difference in elevation between the inlet and the outlet. If the ambient pressure at inlet and outlet are same, then the outlet must be lower than the inlet for a siphon to work.

[@Phylaetra]

I would expect the work necessary would be slightly less from the bottom, as you don't need to raise the first liter of water as much as the last - but I am not sure it would make that much difference in practice... But - I could easily be wrong, I haven't actually worked it out, and there are a lot of cases where intuition can lead us astray!

[@utah20gflyer76]

The correct answer is A because the extra friction of pumping the water through a second 90 degree pipe fitting. The question didn’t mention anything about ignoring minor differences.

[@sparkythewildcat97]

Me, an engineer that hasn't worked on a head problem in forever, just stopping in to make sure I wasn't thinking entirely wrong while looking at the thumbnail haha.

[@haasofdetroit9828]

Crossing out feet for -meters- metres felt like a personal attack

[@ayubshaikh9156]

Well explained,……. I forgot , fooled by the height of the pipe in ‘A’ being same,……!

[@ViciOuSKiddo]

This makes sense because the gravitational pull from Earth is occurring in a single "column", if you will. Like a bunch of slippery sand in a pool and if one section of the bottom has a hole in it... gravity forces that column down like a game of connect-4.

[@gide5489]

You should have considered the pressure from the atmosphere from the beginning. Concerning pool vs sea, you should have considered 1. The salinity of the sea and 2. The altitude of the pool.

[@thevoiceharmonic]

I used to argue with my father about this. He said my approach would work in theory but not in practice, but I would reply that it worked both in theory and practice. My brother was on my fathers side. Neither of them studied science

[@00wheelie00]

Pressure is highest in A until the tanks are level with the top of the pipe in A. A needs max pressure to fill fro the first drops.

[@bobleader9006]

Would the pressure on the pump still be the same as the other 3 examples if the inlet pipe was at the bottom of the side wall?

[@smitajky]

This is all very well but having to pump water a lot I can assure you that tank A takes significantly less power than the other two. And that if you make the end of the pipe into an exponential horn then the pump takes less power again. I know that is beyond the level in the video. But if an engineer was looking at the problem I would expect them to instantly see why one design is more efficient than another. The effective head is the height the water is lifted to PLUS the kinetic energy component in the water velocity.1/2 m v^2 = mgh -> h = v^2/2g EXTRA head needed. In the other two tanks a lot of wasted power is used in turbulent flow within the tank itself. Slowing the water gradually and regaining the kinetic energy is vital to efficiency.

[@mr.bianchirider8126]

What if the diameter of the pipe is very small and the height difference small ? Wouldn’t capillary action reduce the pressure on the pipe that is open ?

[@mgpvii]

Any difference in the friction of the water exiting exiting an open orifice (air-top of tank) vs into water (water-bottom of tank)? I’m disregarding the friction of the extra pipe to the top of the tank for purposes of this question.

[@geoffreymoloney4113]

Wouldn't the bottom filled tanks be preferable because your head slowly increases from zero, while the top fill has to overcome maximum head before it even starts filling the tank?

[@LoneWolfSnowplowing]

I've been wondering about this type of thing on a car project. Let's say I have a sealed tank with 2 fittings in it. 1 fitting near the top, 1 fitting near the bottom. The installation would be cleaner if I pump the water into the bottom fitting and forcing the fluid out the top fitting versus pumping to the top fitting and having it come out the bottom fitting. The pump will be about level maybe slightly below the bottom fitting. So if what I understand from this video is correct, there's no problem with feeding the bottom fitting versus the top. Whether I feed the bottom fitting and it fights the water column to the top fitting, or if I run the hose (from pump) up to the top fitting.....that hose will have it's own column to fight, plus when it comes out the bottom fitting I'll still need to run a hose up above past the tank on to the next component (supercharger)

[@mathewritchie]

Not an engeneer but I think the pipe may add friction and require more pressure to move the water.

[@dracos85]

What if the bottom pipe was moved from bottom of the tank to the side of the tank at the very bottom? How would that change the pressure?