What Happened To My Aquarium Water Pump?

[Boris_yo]

Hello everybody! Thanks to those who tried to help with my previous problem.

This time my water pump stopped functioning and this is second time my water pump failed actually. I bought it with aquarium half year ago. I tried hitting it like i did first time which made it to continue functioning, but this time it did not help. However! It works but does ot function. I hear working sound, feel vibration but it does not pull water in.

Here are its pictures:






What can be done? It says to not operate without water. If i am going to disassemble it, how am i going to still operate it without water?

Thanks.

[Simon]

bin job ! sounds like the impeller has broken off the motor shaft

[Boris_yo]

bin job ! sounds like the impeller has broken off the motor shaft

Maybe i should disassemble and take a look?

[Mechatrommer]

i dont think impeller can get torn apart by water, except if some power abuse is applied, maybe jam due to dirt or worn out magnet/coil. try opening it up, what else can you do other than that? buy new?

[IanB]

Although hitting things is a time honoured repair technique, there are limits to its effectiveness. It sounds like either something is broken or there is a blockage. It says do not operate without water as the water would be required for cooling and lubrication. You could run it briefly without water for testing. However if you open it up you will likely break the water tight seal around the electrical elements and then it will be very hard to seal it up again. It may be best to just buy a new one.

[Boris_yo]

I think i now understand what is wrong here. You see, i am weak in physics. I have noticed that when the water level in aquarium is below the pump's core, it does not pull in water. When water level is above the pump's core, the water is coming out. What i initially thought is that it pulls water directly from tube's end and when i submerged the end of tube into the water, the water did not come out. This is where i thought something does not work.

The rotor rotates and pulls in water now. However is there a pump that does not require water to be above its level?

If somebody could point me to explanation how aquarium pumps work, i would appreciate.

[0xdeadbeef]

A water pump should work no matter where it's located. The system (pipes and the core of the pump) have to be filled with water though as water pump are usually pretty bad at pumping air. Indeed they are usually damaged sooner or later when running dry.

[Mechatrommer]

looking at your picture, it seems like a normal "aquarium" pump. if its similar like the one i dissasembled years ago, the coil is completely sealed with hard glue (top part in the picture), opening it means breaking it, however the impeller/rotor/magnet part is totally exposed to water and can be separated from the sealed body easily. aquarium pump is meant to be submerged and very low suction power, even a slightess air (above water level) and it will fail to suck. see the lining there? i think you can separate the top and bottom part of the housing and look at the impeller inside and then can take it out. anyway, as you said, its not broken at all, so there's less reason trying to fix it now.

[IanB]

I think i now understand what is wrong here. You see, i am weak in physics. I have noticed that when the water level in aquarium is below the pump's core, it does not pull in water. When water level is above the pump's core, the water is coming out. What i initially thought is that it pulls water directly from tube's end and when i submerged the end of tube into the water, the water did not come out. This is where i thought something does not work.

The rotor rotates and pulls in water now. However is there a pump that does not require water to be above its level?

If somebody could point me to explanation how aquarium pumps work, i would appreciate.

This is very normal. The need for the pump to be submerged would also (often) happen with much bigger pumps like swimming pool pumps, fountain pumps and sump pumps.

All of these pumps are centrifugal pumps. They work by spinning water through the rotating impeller blades. If the blades are full of air the pump will just spin uselessly like a car with its wheels off the ground; the pump needs to be primed with water on the suction side before it can work. Basically centrifugal pumps are good at pushing but no good at sucking. If you don't feed water into the pump it can't push it out the other side.

It is possible to get what is called a self-priming pump in some cases, but there is still a limit to what height this will work over, and all centrifugal pumps have a suction height limit anyway called the "net positive suction head". If you exceed the required NPSH a pump will not work properly and may be damaged.

(The above is a very condensed summary from a chemical engineer hanging out on an electronics forum.)

[Mechatrommer]

(The above is a very condensed summary from a chemical engineer hanging out on an electronics forum.)

not bad! alot better than me

[Jimmy]

Sounds like you got a air bubble in the pump. When staring the pump if there is a bubble of air the impeller can spin around freely in the air and it doesn't pump. 

[Boris_yo]

All of these pumps are centrifugal pumps. They work by spinning water through the rotating impeller blades. If the blades are full of air the pump will just spin uselessly like a car with its wheels off the ground; the pump needs to be primed with water on the suction side before it can work. Basically centrifugal pumps are good at pushing but no good at sucking. If you don't feed water into the pump it can't push it out the other side.

It is possible to get what is called a self-priming pump in some cases, but there is still a limit to what height this will work over, and all centrifugal pumps have a suction height limit anyway called the "net positive suction head". If you exceed the required NPSH a pump will not work properly and may be damaged.

(The above is a very condensed summary from a chemical engineer hanging out on an electronics forum.)

Good answer! Is there a pump which does not require water to be fed? Is it self-priming pump that you mentioned?

[XynxNet]

There are two common types of aquarium pumps. Ones like your pump with a more or less sophisticated magnetic rotor and ones which work with a membrane pump, which pumps air bubbles into a vertical pipe.

Today the pumps with the magnetic rotors are standard. They can stop due to clogging of the rotor with plant material or bacterial mats or (big) air bubbles in the rotor chamber. If they don't start most times the rotor is in a "dead" position.

Once working the rotor does not have to be totally submerged because pressure pushes the water inside the rotor chamber. Unfortunately some times the rotor chamber isn't totally pressure tight and some air gets inside in normal operation. The pump gets noisy and doesn't work perfectly any longer. Because of that most people do totally submerge their aquarium pump. 

For short periods of time, like function testing, you can use the pump without water. Obviously it would not pump air, because of it's design. But the real problem is overheating.

[Mechatrommer]

Is there a pump which does not require water to be fed? Is it self-priming pump that you mentioned?

one poster above mentioned... "most pump need to be primed manually". meaning "all pump". but i dont dare to say "all", since i've never seen a pump with high NPSH esp for aquarium use. and if its there, its a big nasty noisy pump that is not for aquarium and not centrifugal type. but, you are free to do the search and let us know