# Eheim classic 250 canister filter making a lot of noise



## Ken Keating1 (Nov 22, 2017)

You may not priming the unit properly. If you are, remove the impeller and check the ceramic shaft. Sometimes they break and need replacement.


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## PlantedRich (Jul 21, 2010)

The low flow indicates there is air around the impeller. Suggest trying this? 
Empty the canister and the entire tubing going from the can back to the tank. In whatever way needed, make sure there is no water in any reactor, heater or other added item in this outgoing line and that the incoming line from the tank to the canister is full. Also make sure the tank water is at a normal level, not low. 
When you open the valves this setup will allow the siphon to start, water will flow down the incoming tube, fill the canister from bottom to top as it forces air out the top until the can and tubing is filled all the way until the water in the filter reaches the level of the tank water. shining a bright light on the can and tubing , you will be able to see this happen. Once it has finished, plugging in will start the motor to boostthe rest of the way up over the tank side and the siphon will continue. 
There are a few things that may not let this happen. Something like a piece of media stuck somewhere in the tubing where you don't see it? A kink in the tubing? 
But a siphon is such a simple process that ,it DOES work and may only leave a tiny amount of air in the canister. This air can be removed quickly by tilting and rotating the can but it will also come out by itself in a few minutes and all should be silent if the impeller and shaft are okay.


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## OVT (Nov 29, 2011)

The filter is sucking in air, most likely from a loose hose connection.


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## PlantedRich (Jul 21, 2010)

If we use a bright light to shine on the back of the tubing we can often see the water moving inside. If there is standing water in the outgoing tube, this can often block the air in the canister from coming through. Definitely true if we have a reactor full of water inline. Air will always go up and pass through water but only if it is always going up. IT will not go down and then up through water! But it often gets confusing when we start the filter and it pumps water for just a bit and then won't! That is often because we start the motor with water around the impeller but then a bubble of air comes down from the incoming line and reaches the impeller. Since the impeller can only move water and not air, it stops moving when the air reaches it. Long term solution is to figure why there is air getting to the impeller and since we can see the bubbles in the tubing, we have a good chance to look and see if the bubbles are there before we start the motor or if they are being drawn in through a leak.


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## utilities21 (Oct 25, 2017)

PlantedRich said:


> The low flow indicates there is air around the impeller. Suggest trying this?
> 
> Empty the canister and the entire tubing going from the can back to the tank. In whatever way needed, make sure there is no water in any reactor, heater or other added item in this outgoing line and that the incoming line from the tank to the canister is full. Also make sure the tank water is at a normal level, not low.
> 
> ...




Actually that’s what happened when I got back from work and went to check on it, everything was silent and the flow had got back to normal ...thanks everyone for all the help 
Next time I have something impeding the flow, I know what to do [emoji1360]



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## PlantedRich (Jul 21, 2010)

Small note if it happens again. The noise is caused by the impeller rubbing and that is usually quiet because there is water around the impeller. There is some hazard in leaving it running too long as the water kind of "cushions " the impeller and shaft. If it runs dry for too long it can score the shaft or impeller. Not a sudden, big thing but over time it does wear them more than needed.


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## utilities21 (Oct 25, 2017)

PlantedRich said:


> Small note if it happens again. The noise is caused by the impeller rubbing and that is usually quiet because there is water around the impeller. There is some hazard in leaving it running too long as the water kind of "cushions " the impeller and shaft. If it runs dry for too long it can score the shaft or impeller. Not a sudden, big thing but over time it does wear them more than needed.




I know I should have stopped it and shouldn’t have let it correct itself 
Thing is I had emptied and filled the canister so many times that I got frustrated since I did not know how to do it right 
I’d keep that in mind. Thanks [emoji4]


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