# Good Impeller v. Bad Impeller



## vaypourus (May 20, 2008)

Since I get asked "what does a bad impeller look like?" quite often, I figured I would post some pictures to demonstrate what a worn impeller can look like. HOBs, canister filters, powerheads, and mag drive pumps will often utilize this style of impeller assembly. Getting substrate (sand, small gravel, crushed coral, etc) or other hard debris sucked up into your filter/pump/powerhead can cause an impeller to wear out. If you are experiencing a lot of pump noise or decreased output, you may want to remove your impeller assembly and give it an inspection.

*The Good*










Here is an impeller assembly from a Tetra HOB filter. You will notice that the magnet body is in nice shape with no circular grooves or wear. The magnet is also not cracked. The impeller body spins freely around the impeller shaft. There is no wobble or play between the magnet body and shaft. No rust or wear is visible on the shaft. When in the filter, it runs quiet and produces good flow.

*The Ugly*










Here is an impeller from a Penguin 160 HOB. You can see that there is significant wear on the magnet body. Deep grooves are visible. The body is so worn that it actually has a taper. If your body looks like this, it needs to be replaced.










This is the shaft removed from the same impeller assembly. This also has substantial wear. The shaft should be a uniform diameter; the step that you see in this picture should not be there. Furthermore, the shaft has begun to rust as it has worn through the chrome plating.

Many impellers come as a full assembly with the magnet, impeller blades, and shaft as one unit. Other impellers (like Eheim canister filters) sell the impeller bodies and the shafts separately. An impeller assembly usually costs between $5 and $20.

It is always a good idea to clean out the motor body/energizer recess (where the impeller goes in the pump) to ensure that no debris is located there. Also peer into the motor body/energizer recess with a flashlight and look for wear. The motor body/energizer rarely needs to be replace, however if you get enough garbage into the recess, it can also wear this part down.


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## BRANT13 (Feb 18, 2009)

TY for sharing :thumb:


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## Maxima308 (Jun 6, 2009)

Can you lubricate the magnet body? I've noticed that a new one will have an oily feeling to it. Would Vaseline be safe? Perhaps this would also increase longevity...


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## jfly (Feb 17, 2009)

nice post.. w2g =D>


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## Cento (Mar 30, 2005)

I'm not sure lubricating will always prevent wear; at least not in the case of the shaft. That kind of wear occurs when the shaft isn't running true (completely concerntric) in relation with the hole in the magnet or visa versa...

Obviously NASA standards aren't necessary on an Aquarium pump impeller, but I guess over time, that wear is inevitable even on the most well made aquarium products.. That being said, I have a 402 AC Powerhead that I've had for 14 years, and its still running..


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## vaypourus (May 20, 2008)

The magnet body does not actually touch the wall of the motor/energizer body in a properly functioning pump. Lubricating the magnet body will not make a difference. Additionally, the magnet body comes in contact with your tank water directly, and any lubrication you used would get into your tank water 

You will get wear on the magnet body when:

1. The impeller spins unevenly around the shaft (due to poor manufacturing or a worn shaft) and allows the magnet body to rub on the wall of the motor/energizer body recess.

2. You get debris between the magnet body and the wall of the motor/energizer body recess.

In my experience, a worn shaft will eventually lead to a worn magnet body, and a worn magnet body will eventually lead to a worn shaft. Either way, you want to get this fixed sooner than later. You don't want a worn impeller damaging your motor body/energizer. A motor body/energizer replacement can often cost 1/2 to 3/4 as much as a new filter, or in the case of a mag drive pump, result in a COMPLETE replacement of the whole unit.


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