Fluval FX6 at tank level having noise issues

Hi,

I have a Fluval FX6 filtering a 110 gallon agricultural stock tank (indoors) which is of course sitting on the ground, so the filter is at the same level. I know it is recommended to have canister filters below the tank but that is not possible here. The water level is higher than the top of the FX6 and I have the hoses come up a couple feet before going down into the water. I also understand that as long as the intake is above the impeller it should be fine. I have been experimenting with various arrangements of the hoses for a long time, and at times I have been able to get it to run completely silent, however it seems after doing filter maintenance something always changes slightly and I will often have issues again with noise and trapped air.

I do not know what changed this time but it is now making a very annoying loud trickling water sound from the top of the inside of the FX6, as if the canister is not completely full and water is dripping/splashing down to the surface inside the filter. To further support this theory if I close the output flow halfway after a while it will stop doing this, presumably because the pressure lets the water level fill properly all the way to the top... but of course flow rate is unacceptably low then. I have replaced O-rings and uses silicone lubricant but it did not change anything. I don't even understand how air gets into the filter like this, it seems like it should be more or less air-tight. Also the intake hose is less than half the length of the output hose, so it isn't an issue of it being harder to pull water in than push water out.

I couldn't think of anything else that could have changed except maybe removing the hoses and re-clamping them repeatedly has made the hoses not air tight anymore? So I ordered a new ribbed hose just in case... but it really doesn't look like anything is wrong with the current hoses.

The output into the water is as high and I can put it but it's basically right at the same height as the FX6. The intake is slightly lower. There have never been any leaks, and most importantly I have been running it this way for about a year and it was not doing this trickling water sound until the last time I cleaned the filter.

I know this is a bit weird of a setup, but I just would like to know what variables could be causing the changes I am experiencing. Any thoughts/suggestions would be appreciated. Maybe there is something more to the physics of canister filters that I don't understand?

Thanks.

 

Is there any way to move the intake higher on the livestock tank, so that there is a bit of drop between the intake and the top of the filter?

 

Not sure if this will help but whenever i start a canister filter i always run the output [return] into a hose going to a bucket lower than the filter. It allows all the air to easily escape. Doubt this will help in your case as return is already pretty low. The important stat is the water level in the tank needs to be a certain distance above the pump.

 

Is there any way to move the intake higher on the livestock tank, so that there is a bit of drop between the intake and the top of the filter?

I just tried that, but in order to have the intake that high the hose connector has to be above the water and I'm not convinced that connection is air-tight. It doesn't seem to have made a difference though.

Not sure if this will help but whenever i start a canister filter i always run the output [return] into a hose going to a bucket lower than the filter. It allows all the air to easily escape. Doubt this will help in your case as return is already pretty low. The important stat is the water level in the tank needs to be a certain distance above the pump.

Well the pump is in the bottom of the FX6 so it's more than 1 1/2 feet below the water surface. I can make one or both hoses go below the water surface below the water surface before going up over the edge of the tank if that would do anything... I thought having them go up well above the filter and then coming back down might help but I don't think it does. I'm still not clear on all the physics for the hose placement other than that the actual intake and output points need to be above the impeller.


Ok so I found this thread here that sounded like a similar problem and was only resolved by getting a replacement unit...
New FX6 making sloshing water noise | Aquarium Filter Forum | 487032

However, they mentioned by wedging something under one side the problem stopped so I tried that and sure enough it is running silent now. So, I wonder if I just have a defective unit. I'm also wondering if the service kit might fix it... Amazon.com

 

Didn't realize the pump was at the bottom of the filter. I would guess there's something bad in the filter causing the issue not your configuration. My guess is the repair kit fixes it, it's a lot of parts. My only other thought would be a restriction on the intake not suppling enough water to the pump.

 

I took apart the intake hose, took everything out of the filter and reseated it all. I had a nonstandard adaptor and intake prefilter sponge on the intake that was making it a little more narrow so I removed that. Powered it up and it filled all the way up and ran silent!........ for about 20 hours. In the middle of the night it started getting noisier over time with the dripping water sound, by the morning it sounded like it was raining inside the filter again. This thing is a nightmare. I ordered the maintenance kit to try that next. After that, there's nothing left to replace unless I replace the motor, which at that point the cost makes me wonder if I should throw the whole thing in the trash and buy a new filter. I can't believe there are no competitors to the FX6. Unless I just haven't looked hard enough, it seems there is no other canister filter of equivalent power and capacity.

 

So your back to stock on the intake side now? No restrictions? Tough problem. Does Fluval have a tech support line? Maybe they can at least tell you if your setup SHOULD work. Is the stock tank rigid? I wonder if you could set it on 4x4's to get it higher? Good luck hope the kit works.

 

You might try turning down the output valve to 3/4 and leave the intake at full. Might help to keep a little back pressure in the filter. I have two FX6's and they are below the tanks. Only time I have noise is with the impeller when it gets sandy.

Oh I also fill the filter full of water before closing the lid after cleaning to help with getting all the air out.

Good luck.

 

I installed the maintenance kit and it did not fix it.
Once it is fully filled with water it runs silent for a few hours, then slowly starts filling with air until it sounds like a rainstorm.

If I didn't need this filter right now I'd throw it in the trash. The noise is driving me insane. I really don't want to buy another FX6 if this one is a piece of junk.

One thing i have discovered is when I shut it off, the air will bubble out and it will refill with water some, but not all the way. then if I shake the whole unit a bunch more air bubbles out and it fills more. If I keep doing this it will get all the air out... but it's not doing it on its own. I don't understand how the inside of the FX6 works well enough to guess why this is happening. Could something be screwed up with the lid? There are no leaks and it seems fully sealed, but air is getting in somehow.

What would be the next best course of acttion besides throwing it in the trash? New hoses?

Also setting the output to 3/4 seems to slow the problem but it will fill with air and make noise eventually... and it did not originally do this, so something is wrong.

 

I know this isn't helpful, but the FX6 instructions are pretty adamant about the need to install it under the water level for it to function properly.

I think you are likely fighting a losing battle expecting it to work 100% correctly otherwise.

 

It almost seems like the filters emptying out before it can fill with water and sucking in air somehow. Maybe Tanks suggestion of slowing down the return to the tank could help? Any kinks in the intake hose that maybes slowing flow down? Running out of ideas here. Going over your original post as long is the water level in the tank is above the filter i would cut the hoses so they don't have to go hi over the tank. Keep them as short as possible.

 

I know this isn't helpful, but the FX6 instructions are pretty adamant about the need to install it under the water level for it to function properly.

I think you are likely fighting a losing battle expecting it to work 100% correctly otherwise.

They always say that but I believe what is actually correct is that the impeller needs to be below the water. I know it's relatively uncommon but 'm definitely not the only one who runs a canister filter on a tank at ground level. I might question this if what I am dealing with wasn't a new issue. I've run it like this for years, it would tend to have minor issues after cleaning it out which could always be corrected by getting the hose placement just right... but this thing where it is basically emptying out the filter slowly and sounding like a rainstorm has never happened before, so I'm pretty sure something is broken. I don't need it to work 100% correctly, I just need it to work like it used to.

 

serqetry , I also have an FX6 with the same issue.

Everytime I unplug it or when it turns itself off for a min every 12hrs, a lot of air comes out the discharge.

Yesterday I cleaned the filter, and applied silicone gasket lube on all the O-Rings. The problem is worse now.

I had to leave it unplugged and turned the valves closed this morning. Tomorrow I'm going to check the connection between the hose and the intake valve. I think air is getting sucked in there.

Try taking apart and reconnecting where the hoses join the intake/discharge valves.

 

So, I made progress. I now have my FX6 running silent, although I have to keep the output valve around only 50%-60% open. Anything more open than that will cause it to empty slowly and start making noise again, so it's definitely a pressure issue at this point.

The thing that changed which allows it to function as well as it is now, is I took apart the inside of the lid. there's some kind of twisty air trap made of black plastic snapped into the center, and then that connects to a white plastic ring that the tube that stays inside the canister fits up into. I unsnapped both those things and cleaned them but I also noticed there was an o-ring (not included in any maintenance kits, which seems really dumb) in there behind the white plastic ring. The o-ring was very loose and flopping around inside there. I took it out and lubricated it with silicone grease, and when I snapped everything back into place I was able to push the white plastic ring much further than before and then the o-ring was completely snug.

So this seems to have increased the pressure, but it's still not perfect obviously. I also notice that my lid and canister seem pretty warped from tightening the clamps so I think maybe my FX6 is just doomed and can no longer be pressurized enough to run silent at 100% output. There's also something stupid still going on where it will never purge all the air out on it's own...I have to shake it while it's shut off to get all the air out. But at least running at 50% seems to keep that amount of trapped air from causing the horrible noise. I am curious what would happen if I just left that twisty air trap thing in the lid out. Maybe I will try that the next time I clean the filter... but I assume it's there for a good reason.

I'm going to just call this semi-success and enjoy the silence until the next time something makes it worse. I sure wish there was a better canister filter out there with the same amount of power as the FX6... but since i'm now running at 50% anyway maybe I should consider other options.

 

Really starting to sound like there's design issues with filter. If everything's not perfect problems arise. There should be some margin in the design to allow these the filter to work in non-optimal conditions. I would try to contact the manufacture to get a replacement, maybe they have some fixes for these issues in the latest models.