Water pressure fountain

[buckleyc]

Good Morning All, I have a spring fed well half way up a hill and want to run a pipe from the well overflow (which is currently running out at c.2L/second. My idea is to start with a large bore pipe (c.110mm) and reduce it to maybe a 25mm pipe to create a fountain at teh bottom of the hill. However, I do not want to spend teh money and then see if it works, I want to calculate what size pipe I need to start with, at what stage I reduce it down to smaller bore pipes, how small a pipe a reduce to at teh end and how high the fountain will be?

 

[Stivino]

It's not enough to say "the well is half way up the hill". You're going to need to know how much higher the start of the pipe will be than the bottom.

 

[buckleyc]

From the top of the pipe to the bottom, the difference in height will be about 20m.

 

[ColJack]

20m head is 2 bar, or 28.4PSI..
but I'm not sure if that still works if it's on a slope..

 

[buckleyc]

That very helpful - thank you. No much of a water fountain though!

 

[ColJack]

i dunno, it's all about pressure..

that's 28.4psi.. so if you use a 15mm or 10mm pipe i'd say it should be quite a jet..

 

[dextrous]

From the top of the pipe to the bottom, the difference in height will be about 20m.

So the height of the fountain should be 20m then, subject to some loss due to friction in the pipe. It will simply "try" to reach the same level that it comes out of the well at. This is nothing to do with the pressure being 2bar at the point of exit of the pipe, but everything to do with basic physics. The wider the bore of the pipe, the greater the flow rate, but there will be no difference in static pressure

 

[ColJack]

you're not going to get a 20m jet of water from a 4 inch pipe though are you..

isn't it more to do with velocity and gravity?
decelleration due to gravity and all that?

 

[dextrous]

you're not going to get a 20m jet of water from a 4 inch pipe though are you..

isn't it more to do with velocity and gravity?
decelleration due to gravity and all that?

If you wanted to mark two points say 50m apart to have exactly the same height, you could use a length of hosepipe filled with water - the water will want to level itself out. The principle is exactly the same here.

 

[ColJack]

that only works because the water is contained..
once in free air then it will go all over the place and won't have the water below it to support it so will fall back down.. while it falls it will strike other water coming up slowing that down..

try it with a hosepipe.. turn the tap on to a trickle and hold the hosepipe end near floor level pointing up.. see if the water reaches the height of the tap..
then put your finger over the end ( so the pressure increases ) letting only a little squirt out.. it will go much higher

 

[TicklyT]

It sounds like 2 litres/second, or 120 litres/minute would be more than adequate flow for a fountain - it's approaching the delivery rate of a fire hose.

A flow rate of 120 litres/minute through a 2" smooth bore plastic pipe would have a pressure drop of something of the order of 1 Metre of head per 100 Metres of pipe. losses are about 3.5 Metres/100 Metres for 1.5", and 0.04M/100M for 4"

The design of the venturi or fountain jet would have the biggest impact on the display. That's where the flow is accelerated to it's maximum velocity in accordance with Bernoulli's principle. IIRC a smooth converging cone with an included angle of no more than 41 degrees generally produces good results.

There could be room for experimentation with a hydraulic ram pump to boost the pressure at the fountain head. They are self-driven, producing a high pressure but low flow rate from a low pressure high flow. A home made one can be built from common pipe fittings.