Backyard Aquaponics
A place to discuss aquaponics

Excuse me! I got it right; picking B in Q1 was correct. If its the same pump as A (even though we didn't know if A was capabable of pumping the required flow to B's GB) its the correct answer.

YEP... .... or some other aeration device or structure ..

I'm going to deduct two points off Frank for changing his answer after seeing the answer -2 Frank

But you didn't provide a reason Sleepe Marks are only awarded if you can show how you got your result. Otherwise everyone would have had a 50/50 chance of getting it right.

That'd be right... post up a multichoice question... then mark it down because the answer does correspond with the markers marking sheet....

There was a typo on the question that you should have known - the question should have read:

Which pump would you buy and why?
My bloody question, I'll change it if I want - that's that bloody smart arse again...[jots down something in a little black book]

My Dad always used to say.... "read the fine print son, read the fine print" ....

Trouble is I usually forget where I left my glasses...

You changing the questions now Myles?

What's wrong with changing the questions to reflect the answer you want Sleepe..

The graph below highlights something important (actually a few things if you read it right):
Source: European Guide to Pump Efficiency for Single Stage Centrifugal Pumps, European Commission, 2003.

Green Line: The theoretically attainable pump efficiency - can't actually be obtained in practice due to reality being, well, reality. [I suspect this is what Frank hopes his pump can achieve.]
Blue Line: The maximum practically attainable pump efficiency - something that the very best, very large industrial grade pump, fully polished inside and out could probably only strive for, and probably never really achieve (None appear to have yet).
The top Orange Line: An average of very large industrial pumps held in the Hydraulic Institutes database. These are big honkin' pumps - in a different solar system to the pumps typically used in AP.
The bottom Orange Line: An average of all the ANSI/API standard pumps held in the Hydraulic Institutes database. Again these are large industrial grade pumps that conform to the ANSI/API standard - on a different planet to the ones typically used in AP.

The pumps typically use for AP, would most likely not fit on this particular graph i.e. they would be below the x-axis somewhere.

The only graph I could find that shows smaller pumps and where they fit is this one:
Maximum Attainable Pump Efficiencies Scroll up a little for the graph.
The graph shows specific speed rather than flow rate, but the two are closely related. Again these are theoretical and not actually achievable in reality.

Note 1: These are pump efficiencies - the losses in the motor/drive are not included, so they really need to be reduce by 80-90%.
Note 2: These tables are not lookup tables! They are just guides.

I thought it was a bit uncouth, but allowed?

please come on, Stuart and Rupert,
and be fair

Frank said no such thing

this is your interpretation of what I might have said
and as such it might concur with my conclusions

but I never wrote this, nor intended to write this
I leave people to draw their own conclusions
so if you think it is leading to the same conclusions, this might be a sign that you agree it might indeed lead to these conclusions

please respect what I do write

which is:
limit pump head to the minimal required, which is the level difference between the vessel pumped from and the vessel pumped to
next avoid all elements which might force you to discriminate between head and total head

the suggested instructions to achieve this are simple and easy to understand: only a vertical, slightly over dimensioned stand pipe to head required is needed

next let gravity take over to bring water back to base (the pump in the sump), meanwhile passing through the fish tank, through the growbeds, to the sump

on every stage, make sure you make the best of all opportunities for passive aeration that appear
and they are many, but seldom exploited

open gutters are one obvious opportunity, your imagination is the only limit to others

frank

myles,
I agree with most of what you wirte
and I have warned for it:
for a centrifugal pump: expected energy efficiency is limited to at the most 60%

but I absolutely disagree with the way you phrase this:

I agree that motor/drive efficiency should be included (clearly shown in the pump efficiency calculator)
but let's say a motor drive to be 70 efficient
that would mean results should be reduced by maximum 30%, not 80-90%

and even that is in most cases not correct:
if the data provided are measured data, all efficiency losses, whether they are caused by the pump, by the piping, by the motor or by anything else, are irrelevant because they are included

as said, a pump has no brain

frank

It's actually more efficient to pump directly to the bottom of a GB, rather than pump to the top of the GB. More flow when the GB is empty, same flow when the GB is full. Flow trumps efficiency again - but it's not practical in most AP GB's.

Ouch, I had meant they needed to be reduce by the 80-90% efficiency that the motor runs at - my bad - must be a problem with my language skills.