Making water circulate based on pressure alone

No. No matter what you do, you will have to overcome friction losses. That will require an additional power source.

By "push the water back into the loop" - do you mean return the water from the tank back into the original source? If so, then no - it is not possible [unless the source pressure dropped of course].

If you mean into another, separate "loop" then it is possible if the pressure is lower than the original source.

I meant "to go back into the same loop." But I guess it doesn't matter. If it is possible to go into another loop so that the pressure will build up enough to push it back into the first loop, that would be cool.

You will have to think out of the box on this one. Think in the direction of a electronic bistable flip flop using water,

The replacement components could be Ram pumps, check valves, float valves and venturi's.

I promise to come back to you (I will need some time in the pub to figure it out)

I think you may be on to something. I'll start thinking in this direction. Good luck at the pub. I'll buy the drinks when we figure this out.

Short answer, "No". Water always finds its own level. Once the level in the tank and outlet pipe are the same, there is no pressure differential, so there will be no flow. The only way to do this would be to couple a hydraulic ram to the tank, but this entails the loss of a small amount of water each time it is used.

It could be "yes", if the expected set-up is as below:

Thanks. Interesting diagram. I'm not sure I understand it completely, though. What are the two boxes in the middle? Why have the two pipes coming out of the bottom of the tank? Have you ever tried this before?

I think the two boxes in the middle are windows for the house, and the two 'pipes' out of the bottom of the tank are actually support legs (the left side of the tank has the inlet/outlet line and a vent)

Sorry, I did not understand your question in the first place.

Later I understand the whole subject is about 'perpetual motion arrangement'. And as many said perpetual motion is impossible. But still some love to deny and wish/see one of that kind should be available.

Well, answering your questions:

- A over-head tank is shown over a house (two box like indications are windows)

- The two line under the tank are just support and nit pipe lines.

In principle it has been proven that perpetual motion is impossible, and thus, there is actually no need to do the math- that's impossible from first principles.

Btw, your question refers to 'hot water' but I don't see what's the temperature got to do with it. It can come downhill without a pump, but I don't see a reason in the world for it to come up again at the same temperature. On a level field the water will be static with no flow. For flow to occur a pressure difference has to occur for some reason, and you are ruling them out in your question. So the answer is no.

OK, everyone start laughing at me now.

I have done this back in the early 90's. I used a tank about the size of a large coffee can with a funnel shaped bottom. I connected a very small diameter tube. Somewhere in the 1/8" diameter range. The tube was just long enough to reach the top of the tank and point back into it slightly but no siphoning effect. I filled the tank until the flow started. The flow was very slow. I hear you laughing and gasping for air. Yeah, well my wife laughed at my idea until she saw it work. A few years later we were visiting friends. They had a 2 small children. My wife was helping fix drinks in sippy cups. These cups were the type that the handle was also the straw. The mother told my wife to not fill the cup too full or it would leak out of the handle. My theory behind the original experiment was that the weight of the water in the tank would over come that of the water in the tube, since the water in the tank was being concentrated by using the funnel. It went against what I had learned in school but I wanted to try it anyway. The flow of water could have initially started due to the filling of the tank. So, I stopped it by placing my finger over the tube. After waiting a few seconds I allowed the flow to continue. Still worked. I had hoped that there would have been enough flow to use this idea to run a small decorative table top water fountain. The flow was so slow that I did not pursue it further.

Capillary action at wpork?

I did not think that capillary action would have taken place in my experiment due to the size of the hose. The 1/8" mentioned was the ID.

Something like this?

http://en.wikipedia.org/wiki/Barometer

On my experiment the top was open, not sealed.

Goethe's device is similar to the design of the sippy cup. Move the spout to the side of the base and it would be used as a the handle / straw.

Thank you!!! I'm not laughing. It's nice to know I'm not the only one who's tried this. Only you succeeded where I did not.

I tried it with a gallon milk jug and a 1/8" (about) diameter tube, but the pressure was never enough to push the water back into the jug. I thought a funnel shaped bottom might be what was needed, but the milk jug had that. I just put the tube in the lid, filled up the jug and turned it upside down. Maybe I'll try the coffee can like you said. Thanks again!

It's been 15+ years since I did this. With all of the problems we are having with global warming the water now a days may not be dense enough to do this any more.

Just kidding.

I am going to have to repeat this experiment now.

If you were holding the handle of the sippy cup (which was also the straw), the heat from your hand could have caused some convection????? Yes...?? No...??

The cup was sitting on the counter top and the lid had a small vent hole. No check valve that I can remember. Here is one on ebay similar to what she had. I don't know if it is the same brand or not. http://cgi.ebay.com/BABY-SIPPY-CUPS-SMALL-AND-LARGE-NEW-NEVER-USED_W0QQitemZ180291747056QQcmdZViewItem?hash=item180291747056&_trkparms=72%3A1205%7C39%3A1%7C66%3A2%7C65%3A12%7C240%3A1318&_trksid=p3286.c0.m14

The design may have been changed to over come the problem. Maybe it was due to capillary action as pointed out by Reid in post #8. I do remember that the level of liquid in the handle was higher than the liquid in the cup. Granted it was not by a huge amount but it was higher.

The drink could have reacted with something in the tube causing CO2 for example.

(calcium reacting with a weak acid in the drink).

By placing your finger you allowed the bubbler to rise or escape at the bottom.

It was just a plain plastic sippy cup. The handle was a zig zag style not straight. I'm not sure of the type of plastic but it was clear with a color tint. The drink was either fruit juice or Kool-Aid, not soda. I know you said, "reacted with something in the tube causing CO2", I am just trying to pass on what was probably in the cup. It's been to long ago to remember exactly. I do not remember seeing bubbles in the tube. I'll look around and see if I can find a cup that style.

You could build a expander /pump that is powered by the water pressure at the tap and then circulates water in a loop.....

Something like this?

Check out this link:

http://www.lhup.edu/~dsimanek/museum/people/people.htm

Good lord this is physics for 14 year old kids!

It is not possible without the injection of some more energy.

The nearest that RLMartin can get to his aim, as hinted earlier, is to divert a small amount of the incoming pressurised water and use this flow to operate a hydraulic motor (vane type or turbine for instance) which then turns a circulation pump in his closed loop.

Regards

Chas

So you think only a "small amount" of the pressurized water could operate the hydraulic motor? That small amount would be lost from the loop, right?

Sincerely,

RL-14-year-old-Martin

We went for a family lunch to a restaurant today and I saw a terrible 2 year old having this zippy cup upside down without juice spilling.

The air vent must have a non return valve. Therefore when the cup i filled and the lid is clipped on the pressure inside will be higher.

As for the CO2 - we have super saturated dolomite water in our taps. any wet object will dry leaving a thin layer of mostly CaCO3. This do react with juice with a ph of 6.

Most, if not all, sippy cups these days have a check valve on the lid. Some of these have a reversible valve. Install it one way and nothing spills but it dispenses slower. Meaning more work for the child to get a drink. The other way will allow some leakage but the flow is much faster. The cup I was talking about only had a vent hole in it, I think. Anyway, the lid was off of it when it was being filled and I noticed the difference in levels. I believe Reid (post # 8) was right about the capillary action causing this. I went to the store yesterday trying to find one of these. No luck. I think I need to save face here. I am searching for one of those cups. If anyone out there has one please fill it up and let me know if it does what I said. I will keep looking around here to try and find one.