Pumps & gph

[debdp]

Yesterday I tried uping the flow to my refugium and switched out my Minijet 404 for the Maxijet 400. The Minijet has a variable flowrate of 18-108gph The Maxijet 400 has a max flow rate of 106gph. But when I switched them I knew the Maxijet had more power but was not aware of its GPH. Well the angle/height of the pipe coming from the refugium (which sits higher) to the main tank wasn't enough and the tank started to over fill. So I killed it and put the Minijet back in.

So my question is: How can a pump rated at 106gph as the Maxijet is, seem to have 2 to 3x the flow of the Minijet which is rated a 108gph.

 

[psteeleb]

pump GPH ratingas are with no vertical head pressure. So, depending on how far you push the water both vertically and through a pipe the ratings will drop off and with some pumps it drops off very fast. Some high GPH pumps will loose most of their GPH with just 1' and may loose all of it within 5'

 

[BigJay]

I have a better question: Is a powerhead really necessary in a sump/refugium?

Outside of the skimmer, I wasn't planning on having any pumps in the water anywhere.

 

[debdp]

Thanks Pete.

The pump is not having to travel far. The distance is up about 6" (inches) and across about 10" but it's at an angle so there is no elbow, just straight 1/2" hose. But even with no vertical/horizontal output I put both pumps in a container and the Maxijet 106 has a much more powerful output than the Minijet.

So is it you can't look at the GPH to determine the output (power of flow) of a pump?

 

[debdp]

@BigJay wrote:

I guess it depends on your situation. My refugium is set to the side and ABOVE my main tank. So the pump is in the main tank pumping water into the refugium. My refugium also holds Sun Corals and they like/prefer lots of flow, so in my case I was trying to create higher flow into the tank to avoid adding a second pump. Since my main tank is currntly only 20g, the refugium is 6g. In your case I'll assume you have a much larger set up and your sump/refugium is most likely below your tank so you probably have a significant amount of water already going through the sump area and you probalby only keep macroalgae in there. So you most likely have no need for an additional pump. But somebody with more sump experience would have to best answer... as this is my deduction and not experience.

 

[psteeleb]

I don't know enough about the minjet - they may overate thier pumps as compared to maxijet (in turn may underate)

but the GPH could be spot on with out any tubing attached. Many small pumps are designed to move water more so then push it. An example; the maxi jet mod, normal factory, has an impellor that pushes water, the mod uses a propeller that moves a bunch more water but you would probably get nothing or very little if you hooked up tubing to the outlet.

 

[Darby]

Reefcentral has a calculator that is apparently absed on real world data that can give you the gph pressure loss due to head height and other factors. I was surprised!