Pump with good head?

[foxfish]

View attachment 215215
There really isn't anything more complicated.
[Hose / pump / hose] + [water in / height difference / water out]

I am sure we have done this before?
Unfortunately for me, your diagram is difficult to understand!
So the pump supply comes directly out of the bottom of the tank through a drilled hole?
I assume you will have a very good quality ball valve to isolate this facility and enable you to safety connecting the pump?
Whatever pump - filter you choose must still be rated for a high head as it will be under considerable water pressure!
I would also recommend ridged pvc pipe as again it will be under near two meters of water pressure.

Your tank has given us quite a bit of entertainment over the years as its unusual shape has never been easy to deal with, I am glad you are still enjoying it too.

 

[hypnogogia]

The problem he’s going to have is that most pumps with that low of an output aren’t going to be able to conquer the 1.5m head.

But the head isn’t 1.5 metres. The downward pressure of water in the tank will cause the water in the return tube to rise to the same level as the tank water, even without a pump. The head is the 1 or 2 cm above the tank level that the pump needs to push the water to get back into the tank.

 

[Bradders]

But the head isn’t 1.5 metres. The downward pressure of water in the tank will cause the water in the return tube to rise to the same level as the tank water, even without a pump. The head is the 1 or 2 cm above the tank level that the pump needs to push the water to get back into the tank.

Funny you should mention this, as that was my thinking as well. However, I contacted Oase about their head measurements as thought I was getting short-changed, and this was their reply:

OASE: "When they measure the flow to produce the flow curve, the max flow is produced and measure direct from the filter as essentially this will be the flow at 0cm, if you are getting roughly 450-500l/hr this would suggest you have the equivalent flow loss of the filter pumping approx 0.8m up. So, with your filter being about 70-80cm below the tank, you then have to consider the length of pipework and restriction through the filter. Changing to a coarse foam will help reduce the restriction through the filter, but with your install the flow you are getting seems about normal."

What I read from this is that Oase actually measures the head from the filter outlet of the main unit, not the traditional head, as mentioned above.

Not sure what is correct and what is wrong to be honest! But if I look at the Oase curve and measure my head from the top of the canister to the water line, then I am spot on at around 450-500L per hour.

 

[Le duke]

But the head isn’t 1.5 metres. The downward pressure of water in the tank will cause the water in the return tube to rise to the same level as the tank water, even without a pump. The head is the 1 or 2 cm above the tank level that the pump needs to push the water to get back into the tank.

I can’t tell from the provided diagram if it’s actually a closed loop or a sump-like application. The verbal description wasn’t helpful, either.


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[hypnogogia]

Funny you should mention this, as that was my thinking as well. However, I contacted Oase about their head measurements as thought I was getting short-changed, and this was their reply:

What I read from this is that Oase actually measures the head from the filter outlet of the main unit, not the traditional head, as mentioned above.

Not sure what is correct and what is wrong to be honest! But if I look at the Oase curve and measure my head from the top of the canister to the water line, then I am spot on at around 450-500L per hour.

From a pure physics perspective, the head height is only the bit above the level of the water in the tank. The distance that Oase is referring to will obviously introduce friction, and that will reduce flow. The further the filter is below the tank, the longer the return pipe and the more friction there is reducing flow.

 

[zozo]

Amazon product ASIN B07L5M2SWZ
It says amphibious pump, but it doesn't need to be, it can be used submersed.

Searching eBay or Aliexpress you might find them cheaper directly from the wholesaler. I've bought and used these in the past and are pretty good pumps. Bought for 1/3 of this price at Aliexpress. But that seems to be past or searching a tad deeper.

http://www.aliexpress.com/item/1005003245464464.html?

As @Le duke previously already explained H Max isn't an issue in primed and looped pipe systems, then it just pushes water around at its Q Max. And it needs to be primed before the pump starts impeller pumps are not self-priming.

The given Q Max from the factory is always measured unrestricted and will reduce with the hoses/bends/valves and or filters in the circuit, so you might get the 1000 but not the 1500 l/h. Since it's a DC12 Volts or DC24 Volts pump and if the label states the Min. startup voltage is probably 6 Volts then you could connect it to a PWM motor controller and regulate its speed (Q max) if you feel it's still too much. Obviously you would need a DC power supply with it.

Anyway as said by others using a circulation pump unfiltered in an aquarium/pond setup will eventually clog up and need regular maintenance/cleaning.