# max head height



## plantnoob (8 Jun 2013)

i see this a lot as im looking at pumps at the moment . am i understanding it right , that it is the max height the pump can return water ? ie a pump with max head height of 2 metres must sit no more than 2 metres below the tank?


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## Rich Jackson (8 Jun 2013)

that's how I understand it, but output would be greatly reduced to almost zero.


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## plantnoob (8 Jun 2013)

the pump im looking at is adjustable from 1200-2300 lph and has max head height of 240cm . would be much less than that though , from a quick measure up , its actually going to be more like 70 to 80 cm


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## Andy Thurston (8 Jun 2013)

Some have a charts telling you what flow is at given head heights
Flow would be nearly 0 at maximum head height but the weight of water from tank will increase the flow a bit too so flow would be 0 @ 2.4m above water level , in theory, but thats not allowing for flow lost through media or dirty hoses


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## plantnoob (8 Jun 2013)

at the moment , im running 1 of these
Aquarium Water Pump Adjustable Flow Rate 1200L/H JP-065  - All Pond Solutions
its a horrible ugly noisy thing ( unbelievably noisy!) its in the tank and is ugly too , oh did i mention its NOISY ? 
i got it because its cheap and had the right sized outlet on for the reactor ive got , and i just wanted to test the system i was going to use .

for the final permanent install im looking at 1 of these pumps
New Jet NJ2300
out of sight in the cabinet . head height will be as said 70 (ish) cm . running at full chat 2300lph through a diy reactor a la foxfish
High flow DIY reactor - now with video | UK Aquatic Plant Society
figure that should still give a good strong flow .


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## Andy Thurston (8 Jun 2013)

Should be about twice the flow you have now
I like the look of foxfish's reactor it looks to work well too. Some people use central heating pumps too, and their fairly quiet. I take it that your pump is just on a loop through the reactor


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## plantnoob (8 Jun 2013)

Yep it's just a loop . It gos powerhead-->reactor-->full length spraybar.


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## sciencefiction (9 Jun 2013)

The quoted flow rates are normally at 0 head height. Manufacturer's saying that 2m is max head height means that if that pump's inlet is positioned 2 meters below the outlet(if outside the tank for example), then it will have theoretically 0 flow at that distance. But that would be even less in practice, because it doesn't take into account the size of the hoses used, connector diameters, bends, obstructions/media, etc..


I've been using and Eheim 1250 external pump and noise wise it's non-existent.


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## plantnoob (9 Jun 2013)

i do like eheim but those pumps are a bit over budget at the moment


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## ian_m (10 Jun 2013)

sciencefiction said:


> The quoted flow rates are normally at 0 head height. Manufacturer's saying that 2m is max head height means that if that pump's inlet is positioned 2 meters below the outlet(if outside the tank for example), then it will have theoretically 0 flow at that distance. But that would be even less in practice, because it doesn't take into account the size of the hoses used, connector diameters, bends, obstructions/media, etc..


Not quite correct. The head height is the maximum height the pump will pump to with zero flow, normally for aquatic pumps in 1-2 meter range. Size of pipe, bends, diameters etc doesn't make any difference to max head height there is no flow. Size of pipe, bends etc only makes a difference to the flow.

If you are making a "loop" with the pump, ie inlet and outlet are at the same height, as in an external filter, then max head height doesn't matter (as the head height is zero in this case) and what matters is the pumps maximum flow rate and number of pipe bends, corners, diameters etc.


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## sciencefiction (10 Jun 2013)

> Not quite correct. The head height is the maximum height the pump will pump to with zero flow, normally for aquatic pumps in 1-2 meter range. Size of pipe, bends, diameters etc doesn't make any difference to max head height there is no flow.


 
It does in my opinion.
The head height is actually the amount of pressure the pump can apply to push the water up. When you have a narrower than ideal pipe, the pump needs to put more pressure in order to push the water up, and in the same logic it needs less pressure with wider piping and no other obstructions. So a pump obstructed by narrower pipes, bends, etc.. will need to work harder to apply enough pressure and that will affect the head height/the vertical distance it can manage to push the water up to. Which of course in turn is another thing that adds to the pressure needed by the pump. The higher the head height, the more pressure needed by the pump to push water.
Basically they are all related and depend on each other for maximum performance.


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## ian_m (10 Jun 2013)

sciencefiction said:


> It does in my opinion.
> The head height is actually the amount of pressure the pump can apply to push the water up. When you have a narrower than ideal pipe, the pump needs to put more pressure in order to push the water up, and in the same logic it needs less pressure with wider piping and no other obstructions. So a pump obstructed by narrower pipes, bends, etc.. will need to work harder to apply enough pressure and that will affect the head height/the vertical distance it can manage to push the water up to. Which of course in turn is another thing that adds to the pressure needed by the pump. The higher the head height, the more pressure needed by the pump to push water.
> Basically they are all related and depend on each other for maximum performance.


Wrong.....pressure for a column of liquid is given by P=hρg.

P=Pressure in Pascals, h=height in metres, ρ= density in Kg/m3 and g=acceleration due to gravity (10m/s2). No where in this simple equation is the size of pipe, bends etc needed. Fundamental school boy physics.

Doesn't matter if the pipe is 10cm in diameter or 4mm in diameter, or has 50 million bends in it the pump will only pump to its max head height given by P=hρg.

Here bursting of barrel depends only on height not on type or pipe.
Pascal's barrel - Wikipedia, the free encyclopedia


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## niru (10 Jun 2013)

ian_m said:


> Wrong.....pressure for a column of liquid is given by P=hρg.
> 
> P=Pressure in Pascals, h=height in metres, ρ= density in Kg/m3 and g=acceleration due to gravity (10m/s2). No where in this simple equation is the size of pipe, bends etc needed. Fundamental school boy physics.
> 
> ...




Thats true only ideally. With friction drag the inner area of the pipe surface ratio to the volume rate of water flow is imp. This ratio is radius dependent..  Most of our pumps are pressure head limited in the sense that the magnetic propeller can throw only a mam weight of water. Per unit time this weight of water depends on hose diam. So if you work out all details there is an optimal hose size for our pumps... 

Sent from my GT-N7000 using Tapatalk 2


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