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Hi guys, I recently bought a used sunsun canister filter (303A). Filled it up with media and water to get it primed easier but there's this problem, the filter outlet keeps blowing out air along with water, causing inconsistent flow rate and it stops working after a few hours. been trying to figure out what happened but just couldn't find the source of the problem. The screw nuts and connecting parts are all tightened up. could it be trapped air or some air leak?? if so, where's the most common component which has this problem?

Check the o-ring (might need lube) and hose seals. Check to see there are no cracks on the inlet pipes. After you prime it, let it sit a few minutes. Then after it is running, unplug and let it sit for a few more minutes. This applies to most canisters, not just the sunsun.

steve wrote:Check the o-ring (might need lube) and hose seals. Check to see there are no cracks on the inlet pipes. After you prime it, let it sit a few minutes. Then after it is running, unplug and let it sit for a few more minutes. This applies to most canisters, not just the sunsun.

There's a small crack at the inlet pipe(made of plastic) which is fully submerged. It's a connecting piece between the J-hook and the inlet strainer. Could that be a problem?


Edit: Btw, I realised this problem can happen without any strainer or connecting parts. I did a test with just the hoses, the same problem occurred again. Bubbles and air kept coming out from outlet.. the inlet hose is much more shorter than the outlet though...

There's no water leaks also.

If the crack is under water, it's not the problem but you will want to replace it. Did you let unplug it like I described? Is the inlet too close to the outlet?

steve wrote:If the crack is under water, it's not the problem but you will want to replace it. Did you let unplug it like I described? Is the inlet too close to the outlet?

So I should replace it? But why? Can I just silicone it? And nope not yet, because I have not assemble back the connecting pieces, will do once I have the time to. The inlet and outlet are placed at each corner of the tank, hence they are quite far apart.

The crack will worsen, making the fitting loose. If it's loose, the intake cover is not as secure, and could cause a trapping issue. Either replacement parts or PVC, it should be an inexpensive fix.

steve wrote:The crack will worsen, making the fitting loose. If it's loose, the intake cover is not as secure, and could cause a trapping issue. Either replacement parts or PVC, it should be an inexpensive fix.

Oh ok got it, thanks! Tried unplugging and letting it work after a few mins, didn't work for me. I tried placing a power head to the inlet to push all the trapped air out. When I plug it on again, it works well without any bubbles or sort but after 15 seconds or so, the problem came back again..

Not sure how readily available SunSun parts are, you might want to go with PVC.

Try priming it, leaving it unplugged and rock the filter back and forth a little. Is the filter below the tank?

steve wrote:Not sure how readily available SunSun parts are, you might want to go with PVC.

Try priming it, leaving it unplugged and rock the filter back and forth a little. Is the filter below the tank?

It's next beside with the tank. I had no issues with the other canister running beside it.

This canister is driving me nuts.. could it be impeller problem?

Is there too much slack with the hoses? Can you lower it?

steve wrote:Is there too much slack with the hoses? Can you lower it?

Nope, I've cut it to the shortest length as much as possible.

Its a sun sun. They tend to leak air all over. I no longer recommend them. Sorry for your problems.

Kansasslider wrote:Its a sun sun. They tend to leak air all over. I no longer recommend them. Sorry for your problems.

Really...? I bought on impulse because there are good reviews about sunsun canister. Damn, what a waste of money and time man

From what I understand the problem is the intake and output. I'm not sure as I have never owned one. I'm sure what ever is causing it can be fixed. Sorry, wish I could help more. You should read this maybe it will help.
http://www.americanaquariumproducts.com ... ilter.html