Staging filtration before and after an inline pump

[knifegill]

What I do know:
For the water returning from the pump to the tank, a fine mesh filter should come before the biological media to keep it clean and functioning. This can be done in many stages and to suit one's taste but basically boils down to keeping genuine raw tank debris out of the biological filter. I plan to use paint strainer bags in the fashion of filter socks, and surround the bag (or layer of bags) with sponges, lava rock and the like. And all this will happen inside a maniacally scrubbed and soap-free kitchen sink. From the sink, it will drop back into the tank. Seems fine and dandy, right?
What I don't know:
But wait! What about the intake/uptake from the tank into the pump? This is not an impeller-type pump. It's a dry-mount type that simply moves the water through, but isn't submersible. I don't even know if I can take it apart without ruining it. I must ensure the parts stay very, very clean. But if I baffle the intake with mesh, large-pored sponges, etc., won't the motor take a toll as the stuff slowly clogs? Even with regular maintenance the poor thing would eventually burn out, right? I'm totally confused. Does my filter pump need a filter?

 

[Toby_H]

For aquarium use we use magnetic driven pumps. In this style the motor moves within the motor housing and the impeller moves within the impeller housing. These two housings are sealed housings with no flow between them. The only connection is via magnet.

In this set up when (when not if) there is restriction, the impeller will 'slip' from the magnetic connection as necessary. Thus the impeller may turn fewer rpms than the motor without any damage occuring.

When the impeller is stuck (not moving) but the motor is moving at full speed, this can cause magnetic friction resulting in over heating and eventually wear and tear. But as long as the impeller is moving at (estimating) half the rpms of the motor there will be no measuable friction heat occuring.


Straight Drive pumps are a whole different approach. In this set up the impeller and the motor are connected by a solid shaft. These pumps can stand up to more resistence with no loss of flow. As the solid shaft connection is far stronger than the magnetic connection they are ultimately more efficient pumps.

But, and this is a very important but, in aquarium use we use media (which causes resistance), usually have an element of head pressure (more resistence), that media clogs (even more resistence), mocrorganisms (bacteria, algae, etc) grows on everything (more resistence), etc, etc. The result of all of this resistence is the impeller will slow down, which slows the motor down. When the back of the motor is trying to move at 100% of it's rpms, but the front of the motor is only capable of moving at a fraction of that rpm rating... the inevitable result is wear & tear, friction and the resultant heat. This will wear out your pump, usually pretty darn fast.


This Straight Drive pumps are typcially used in systems with a given amount of resistance that is designed not to increase. A pool filter is a great example of this. The sand bed media has a given resistence4 and as it gets dirty it does not 'clog' thus the resistence stays the same. The water is filled with chlorine preventing mocrorganisms from developing. The filtration is a closed loop system not experiencing any head pressure. The hoses are all large diameter thus minimuzing resistence. In this situation it is quite simple to find a straight drive pump designed to withstand the resistence the system offers.

In aquarium use, the resistence is much higher and increases with age. Thus the typical resistence in an aquariums filter is higher than a straight drive can handle.


And additional concern is most straight drive pumps require being 'oiled' every so often. A small portion of this oiul will leack into the water it is pumping. It's not enough to harm a swimming pool (due to volume) or to pollute a stream (minimal contact), but in an aquarium with it's restricted volume and continuous recycling, it can be a problem. I will confess that newer straight drive pumps may have better seals preventing this concern. I'm far more 'up to date' on aquarium pumps than non aquarium pumps.


So if you have a straight drive pump, you may want to consider investing in a magnetic driven pump.

 

[knifegill]

Oh, darn. You make a lot of sense in the bad news department. So here's what I'll do. I'll use the pump and do my best to maintain it, and when it dies, I'll get an impeller-driven model. Thanks for the info breakdown.

 

[Toby_H]

and when it dies, I'll get an impeller-driven model. Thanks for the info breakdown.

Magnetic Driven...

While there are all sorts of 'slang terms' to describe them... the two industry standard terms are "Magnetic Driven" and "Straight Drive".

I sometimes feel very anal with termonology, but using the right word when making a purchase can make a world of differnece.

 

[dawnmarie]

I sometimes feel very anal with termonology, but using the right word when making a purchase can make a world of differnece.

Spelling is impotent too.
I'm just sayin'.

 

[iloveoscars702]

Spelling is impotent too.
I'm just sayin'.

really?

 

[Cakilla]

Spelling is impotent too.
I'm just sayin'.

hahahahaha!

 

[knifegill]

Magnetic-driven. Got it. But should I spell it incorrectly, I'd hate to become impotent, especially if termonology would have made a differnece.

 

[boldtogether]

Magnetic-driven. Got it. But should I spell it incorrectly, I'd hate to become impotent, especially if termonology would have made a differnece.