Backyard Aquaponics
A place to discuss aquaponics

Thanks Aquadict.
Thats just great information - I will need to read it over and think about what you are saying a few times! but I gather the main gist is to go for the 2000 Lph pump for best results and dont stock over 20 kilos.
Youve taken alot of the work out for me and I really appreciate it . I hope it helps others out for calculating pump requirements

Cheers mate
Aeon

Aquaddict wrote:

More pump than you need is fine, to an extent, you can redirect it for aeration or in pond circulation.

I agree. Go with the meatiest component you can afford. I bought a beast of a pond pump for my outside ponds when I wanted to create a waterfall.

It is rated at 5000 L / h at 2 m so for my system it will be excessive. I am therefore putting in a T on the pump outlet with a tap on the bypass end to use for aeration. As I increase the bed or in my case tower volume I can throttle the bypass back.

Remembering this is 2000 litres at the highest point....

Head of the pump means a lot in terms of flow. And a venturi can take away as much as 20 percent but as long as you have sufficient waterfall (say 30 cm) you won't need a venturi.

So the pump will more likely be 4000 lph plus adding height considerations. The flow required is 2000 lph at given head.

side of the box usually has a flow Vs height graph you can use. Will be different for each pump style and impeller design

The whole thing about pump size is a bit subjective really, Go as big as you can, a centrifugal type pump can always easily be valved back to reduce the flow without any damage to the pump, so long as the flow is not stopped altogether. It is better to have too much capacity so you can accommodate extra grow beds. (I am finding now that there is never enough grow beds)
A good quality pump will serve you for many many years so it is the least expensive in the long run.
The down side to a bigger oump is the extra power it will burn, although remember it burns less than the rated amount when the load is lower.
Muzza

Wow, how much less power Murray? Say I throttle a pump back to 50%, would i save 50%, 10%...

In asking, I have learned to trick more head out of pumps using reducers, must experiment more before I post findings but the power saving is a definate consideration. Seems as soon as you get over 1.5 metres head the wattage required goes right up in pumps, so I am looking into forcing yet more out of submersibles.

Power useage is not directly proportional, some power us used just to keep the motor running, but in general, less load = less power burn.

It is a bit like your car, flat to the floor going up a hill burns much more fuel compared to cruising along a level highway. Same concept.

Pumps from reputable manufacturers quote the watts burn at full load.

Some pumps from cheap destinations burn much more that quoted on the label.

Muzza

I have found in industrial pumps anyways, centrifical, when you choke em off or as you add more restrictions, (more piping more bends) they have to work harder and there-by more amps are used. So size does matter. I think by adding a 90 degree bend in the discharge its the same to the pump as adding another four feet of pipe. If memory serves which it probaly don't but hopefully you get the idea.

Yes Gotfish, adding distance and bends to a system adds load, (increases inefficency) but over the very short distances we pump water in Aquaponics it is not much of a factor.
The strange thing about a centrifugal type pump, is that it reaches a point where it is at full load then it will loose the load and "gurgle" so in the end as a general principal the load is proportional to the water actually delivered.
We are talking about simple single stage centrifugal pumps, not multi stage pressure type pumps when we use most submersibles.
Muzza

True that.

Murray is correct about centrifugal pumps, the same applies to centrifugal air blowers. When tested on the bench the lowest current draw is when you completely blank off the outlet! and you can hear the motor increase in rpm.

Always throttle centrifual pumps on the OUTLET, not the INLET.

Steve

I've been reading through the posts but haven't seen a $ figure (I know electric prices keep going up); but can any one give a rough estimate on how much their pumps costs to run?

Also what about noise?

Anyone out there doing continous flow? Do you have your pump running 24/7 or a float controlled pump which fills a header tank?

E2

E2 - I run continuous flow 38w pump (24/7):
noise factor - zero, I can be ~ metre from the pump and not hear it over the background noise (and before anyone asks - I don't wear a hearing aid )

running costs - pretty low, there was some figures thrown up to calculate cost but not sure where it is.

I was at Murray's place and I think he has 8,000lph pump running on a timer and that had very little noise also

ca'nt be bothered digging around for a power bill, but if i remember correctly 1Kw/h cost me about 12 cents.

i have a 35W pump running 24/7

12 cents x .035=

.42 cents per hour
10 cents per day
70 cents per week
36 dollars per year

If there is a down side to Aquaponics it is the fact that one has to have a pump or two to make it work. (pity) I am now running a 700 watt x 15,000 lph in my fish tank, but it is throttled back a fair bit. Assuming it is going at 3/4 power burn and using Steves calcs it is going to cost 675.00 per year to run in continuous flow, but it only runs for 3 minutes every 30 minutes, so it is only going to cost approx 67.50 per year to run.
Then there is the sump pump, which is a 280 watt pump. It runs more often so I guess it is going to burn 30.00 per year.
Total running cost = about 100.00 per year

Mate, If I cant get more that 100.00 worth of Lettuce a year (not counting Tomatoes and all the other stuff) from my system, my name is Brad Pitt

I was running a 280 watt x 8000 lph pump which was great for one grow bed, ok for 2 grow beds, but was at the edge of its capacity filling 3 grow beds.

Go for a good quality pump that has more capacity than you think you need, it's better in the long run. I have tried the eb china specials, they are as noisy as hell and the watts and head they claim is a load of old cobblers.