does restricting flow with line valve impact pump life?

[kcress]

Sorry to counter folks but restricting the output flow of a centrifugal pump does not hurt it one bit, unless you cut off the flow entirely, which can cause overheating, unless the pump is a submersible then even that won't likely over heat it if you are talking small aquarium pumps.

When you restrict the output the motor's load goes down. The motor speeds up because it isn't working as hard. The energy consumption goes down too. If you bypass then you continue to consume unneeded power and add more heat to the water.

It is a common misconception that this hurts a motor. Typically it is born of kids playing with vacuum cleaners. Plug the hose and the motor whines up! "Must be bad for it!!" No. It is the motor speeding up because it just got unloaded.

Restricting the inlet of a centrifugal pump though, is bad. This causes the pump to create a vacuum on the inlet side. The vacuum can give way to the water boiling in the inlet housing. Not because it is hot but because it has such low pressure on it. These bubbles can actually peen the impeller causing damage.

Better would be to run the correct size pump though. You can yank this one and use it to mix batch or save it for a backup, etc.

So to repeat. You can block the output down to about 5% with lowered power consumption and no damage. Instead the motor will likely last longer. Block the inlet.. and the motor will make noises and fail rather soon.

 

[Umbra_Vipera]

:iagree:

While I do agree with kcress, there can be advantages to recirculating the water back through your sump/fuge.

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As you can see in the image (on the extreme right) I have installed my return pump just as was suggested here. In my case an external pump. Water flows from the fuge through a 1 1/4" union ball valve to the pump. Then out of the pump through another 1 1/4" union ball valve to a tee fitting. I placed a ball valve on the tee going toward the fuge. The union ball valves are for pump maintenance only. They are not used to restrict flow at all. The ball valve on the fuge return is where I control the amount of water flowing to the display. In reality however a gate valve here would work best.

Back to the point. By using this method I have in turn created an area of turbulence, which is the same chamber where I pull the water from to return to the display. In so doing, I have increased the gas exchange possibilities of the surface water. This may also prove to be a good place to "tumble" some macro algae. Also, by returning the water back to the return, I have slowed the rate of water through the fuge to ensure adequate biological filtration in the fuge.

Obviously, you have to look at your specific situations to see what would work best for you.

 

[kcress]

Is that tinfoil here and there Umbra? Your sump area is very bright and visible compared to most - dark and inscrutable.

 

[Umbra_Vipera]

Is that tinfoil here and there Umbra? Your sump area is very bright and visible compared to most - dark and inscrutable.

Yes and no. It's actually duct insulation. The self adhesive stuff from Lowe's. I was having a small noise issue so I used that to help muffle the sound. Come to find out however, I had incorrectly sized one of my union valves. Once I replaced that the noise dropped considerably.