Pump comes after filter?

[Waterbug]

A siphon works by reducing the pressure at one end of a pipe resulting in the fluid being forced by atmospheric pressure towards the end of the pipe with lesser pressure. Gravity plays play little if any part of this physical phenomena.
The engineering site is correct in this case.

Now siphons...for anyone who cares: Licence 2011. Also see Gurung 2014. Siphons work in a vacuum and there are lots of pumps used on space vehicles and in space suits.

 

[Meyer Jordan]

there are lots of pumps used on space vehicles and in space suits.

Right....and they are all inside either the space craft or suit where there is no vacuum.
And all of this has absolutely nothing directly to do with plumbing Alex's pond!

 

[sissy]

to e simple is the easiest and cheapest lava rock and a stock tank and tank adapters and you are done .More you do sometimes the more it costs and then if it is not doing the job is it worth all the work and expense

 

[Usman]

A siphon works by reducing the pressure at one end of a pipe resulting in the fluid being forced by atmospheric pressure towards the end of the pipe with lesser pressure. Gravity plays play little if any part of this physical phenomena.
The engineering site is correct in this case.

You are right of course, but we could nitpick about the meaning of the words "pull" and "suck"...not very exact terms. Certainly lots of pumps are installed above the water level and there are benefits like in some cases eliminating flooding in rain storms and shorting out the pump. So I would say those pumps are "pulling" or "sucking" in water. The same is true when a pump is below water level. Position of pump relative to water level affects how a pump is primed. But once primed and the pump is running I'd call it a sucking or pulling action. Same as when we suck on a straw. Water can't really be pulled of course, but close enough.

Crane Engineering's definition really chaps my hide by saying atmospheric pressure pushes water...I hate junk science. Gravity causes water to seek its own level, not atmospheric pressure. If the earth lost its atmosphere water would still stay in place, pumps would still work, we wouldn't float off into space. Crane Engineering's web site was probably written by a marketing intern.

neither is responsible solely since siphon has been performed in vacuum successfully without air pressure and also have been done using co2 , more like started by air pressure in tube then gravity plays role

Gravity, pressure and molecular cohesion were the focus of work in 2010 by Hughes at theQueensland University of Technology. He used siphons at air pressure and his conclusion was that: "The flow of water out of the bottom of a siphon depends on the difference in height between the inflow and outflow, and therefore cannot be dependent on atmospheric pressure…"[28] Hughes did further work on siphons at air pressure in 2011 and concluded that: "The experiments described above demonstrate that ordinary siphons at atmospheric pressure operate through gravity and not atmospheric pressure".[29]

The father and son researchers, Ramette and Ramette, successfully siphoned carbon dioxideunder air pressure in 2011 and concluded that molecular cohesion is not required for the operation of a siphon but that: "The basic explanation of siphon action is that, once the tube is filled, the flow is initiated by the greater pull of gravity on the fluid on the longer side compared with that on the short side. This creates a pressure drop throughout the siphon tube, in the same sense that 'sucking' on a straw reduces the pressure along its length all the way to the intake point. The ambient atmospheric pressure at the intake point responds to the reduced pressure by forcing the fluid upwards, sustaining the flow, just as in a steadily sucked straw in a milkshake."[1]

Again in 2011, Richert and Binder (at the University of Hawaii) examined the siphon and concluded that molecular cohesion is not required for the operation of a siphon but relies upon gravity and a pressure differential, writing: "As the fluid initially primed on the long leg of the siphon rushes down due to gravity, it leaves behind a partial vacuum that allows pressure on the entrance point of the higher container to push fluid up the leg on that side".[2]

The research team of Boatwright, Puttick, and Licence, all at the University of Nottingham, succeeded in running a siphon in high vacuum, also in 2011. They wrote that: "It is widely believed that the siphon is principally driven by the force of atmospheric pressure. An experiment is described that shows that a siphon can function even under high-vacuum conditions. Molecular cohesion and gravity are shown to be contributing factors in the operation of a siphon; the presence of a positive atmospheric pressure is not required".[30]

Writing in Physics Today in 2011, J. Dooley from Millersville University stated that both a pressure differential within the siphon tube and the tensile strength of the liquid are required for a siphon to operate.[31]

A researcher at Humboldt State University, A. McGuire, examined flow in siphons in 2012. Using the advanced general-purpose multiphysics simulation software package LS-DYNA he examined pressure initialisation, flow, and pressure propagation within a siphon. He concluded that: "Pressure, gravity and molecular cohesion can all be driving forces in the operation of siphons".[3]

In 2014, Hughes and Gurung (at the Queensland University of Technology), ran a water siphon under varying air pressures ranging from sea level to 11.9 km (39000 ft) altitude. They noted that: "Flow remained more or less constant during ascension indicating that siphon flow is independent of ambient barometric pressure". They used Bernoulli's equation and the Poiseuille equation to examine pressure differentials and fluid flow within a siphon. Their conclusion was that: "It follows from the above analysis that there must be a direct cohesive connection between water molecules flowing in and out of a siphon. This is true at all atmospheric pressures in which the pressure in the apex of the siphon is above the vapour pressure of water, an exception being ionic liquids".[32]

 

[Meyer Jordan]

Let's get back on topic.

 

[sissy]

I would guess that the only pumps that pull water would be external if that is what poster is going for and willing to give it a try and use a mechanical filter .

 

[Mucky_Waters]

Let's get back on topic.

Hard to get that lid back on that can of worms you opened eh Meyers?

Now tell me, are electrons pushed or pulled in an electrical current?

Actually my understanding of why you want to "push" water through most pumps rather than "suck" it is because of the phenomena of cavitation which can severely reduce it's efficiency and will damage the pump if allowed to go on for long enough.
However, there are pumps that are designed to "pull" water better than others, they just aren't as efficient at moving water as most pond pumps are so they are seldom used in a pond environment.

 

[Meyer Jordan]

Hard to get that lid back on that can of worms you opened eh Meyers?

Now tell me, are electrons pushed or pulled in an electrical current?

Actually my understanding of why you want to "push" water through most pumps rather than "suck" it is because of the phenomena of cavitation which can severely reduce it's efficiency and will damage the pump if allowed to go on for long enough.
However, there are pumps that are designed to "pull" water better than others, they just aren't as efficient at moving water as most pond pumps are so they are seldom used in a pond environment.

Well, if clarifying a point for the OP before a costly mistake may be made is opening a can of worms then I am guilty and will continue to be guilty in as much as this Forum exists for pondkeepers (present and future) to learn truth from fiction.
As to whether or not some pumps may be designed to pull is irrelevant to this discussion for, as you say, they are not designed for use in a pond environment.

BTW: The name is Meyer, not Meyers.

 

[Mucky_Waters]

Well, I'm guilty of "pulling" water with a pond pump. Meaning I've run pumps with very little head pressure but with a restricted intake. Probably a lot of people are guilty of this and don't even realize it. Anytime a submersible pump's intake screen starts getting plugged (a very common problem) it has to work harder to pull that water through the restriction and it's going to create more of a vacuum on the intake side of the pump. At some point, when the restriction reaches critical levels, cavitation may start to occur and you'll start to see internal damage to the pump. Fortunately designers anticipate that the pump users will neglect cleaning their pump intake screens and design the pumps to be cavitation resistant, This generally just means not having as close a tolerances between certain areas of the impeller and pump housing, but that also means the pumps will not be as efficient at moving water. So it's a trade off between building a super efficient pump that pumps a lot of water while using very little electricity, or building a very robust pump that can be neglected (not cleaning the intake screen) for long periods of time without damaging itself.

BTW: The name is Meyer, not Meyers.

My mistake,,,, sorry.

 

[Meyer Jordan]

Getting back to Alex's original inquiry..........Given that this will be a 15,000 gallon pond, a single pump will not be adequate. As @Waterbug alluded, as many as three (3) pumps may be required especially if a sieve is to be incorporated into the mechanical filtration. In addition, there is some doubt whether enough space is available to accommodate the size (SSA) gravity-fed filter required to provide sufficient biofiltration for a pond this size.
There are some design issues that need to be resolved.

 

[Usman]

Well, I'm guilty of "pulling" water with a pond pump. Meaning I've run pumps with very little head pressure but with a restricted intake. Probably a lot of people are guilty of this and don't even realize it. Anytime a submersible pump's intake screen starts getting plugged (a very common problem) it has to work harder to pull that water through the restriction and it's going to create more of a vacuum on the intake side of the pump. At some point, when the restriction reaches critical levels, cavitation may start to occur and you'll start to see internal damage to the pump. Fortunately designers anticipate that the pump users will neglect cleaning their pump intake screens and design the pumps to be cavitation resistant, This generally just means not having as close a tolerances between certain areas of the impeller and pump housing, but that also means the pumps will not be as efficient at moving water. So it's a trade off between building a super efficient pump that pumps a lot of water while using very little electricity, or building a very robust pump that can be neglected (not cleaning the intake screen) for long periods of time without damaging itself.


My mistake,,,, sorry.

very interesting and no foot valve one way valve in submersible pumps thats needed to lock the flow and pressure while sucking , may b it exists in external ones

 

[Waterbug]

Right....and they are all inside either the space craft or suit where there is no vacuum.

Lot's of pumps are used outside space vehicles and suits.

 

[Meyer Jordan]

Lot's of pumps are used outside space vehicles and suits.

Example(s)?

 

[Becky]

Lot's of pumps are used outside space vehicles and suits.

Example(s)?

This is not relevant to the original question, let's keep things on topic

 

[alex chappelear]

View attachment 97292
NOTE: Sieve has its own dedicated pump.

Or-
View attachment 97293

I think im replying in the right place.

on these diagrams shouldn't the waterline in the filters be lower than the ponds waterline, how do you know how much lower to make it?

also shouldn't sieve be before sediment chamber to get stuff out of water before it dissolves? and to people with sieves before their sediment tanks, do you find anything even in your sediment tanks if you have a sieve? if so what size is your microns?

what is the "balance pipe" for

why shut down the sieve in winter but keep the other stuff going?