Adjusting a stockman silencer

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Aquarium Advice Freak
Feb 4, 2005
Just got a lifereef overflow box up and running. The "silencer" that came with it, the stockman modification of the durso standpipe, is gurgling quite loudly. It has the airtube coming out of the top cap. If this gurgles, does that mean there is too much or too little air being sucked through the airetube? Do I need to add a valve to decrease the air, or a bigger hole to allow more air?

The flow is exactly what I need. I'm happy with it- but, the noise is very loud. Might adding the reverse durso tee design to the output in my sump quiet the gurgle as well?

If I need an airvalve, is there a place online where I could grab one?

Enough questions for now. Thanks.

- Skins
Is the level of water in the overflow fluxuating or staying constant? Changing levels indicates that the hole is too small and a partial siphon is created. Steady levels I'd guess is either a hole too large, or just plain old noisy.

Any major fish supplies place should have airline fittings. You can't find them locally? The shipping would be much more than the price of the fitting.

I've seen plans for a scilencer recently, but I can't remember where. It had a section of pipe with an end cap on each end. The caps were drilled for rigid airline, and one of those rigid airlines was attached to the standpipe hole. I'm guessing it works like a shock absorber, the air inside the tube may change pressure faster than it sucks air from the far end opening.
Yeah, I'm using the silencer that came with the unit, but I made one as well - both are the designs that you're speaking of. Mine uses a 2" coupling, the one that came with this uses a 1 1/2" coupling. I figured the one that came with it was probably better...I was wrong. Yes, the water level fluctuates.

I changed out the silencer that came with the overflow box with one that I made myself - it handles more water and I'm getting max flow out of the box now (no need to throttle back on my return pump anymore). It is a little quieter in that every now and then the water rises a little in the external box and it's silent for about 20 seconds, then the water goes back down and gurgles. Right now, the cap has one hole with a tube sticking out of it.

So, dskidmore, you're guess is this means not enough air? So, in addition to this hole with the tube, perhaps I should drill a 1/8" hole next to it? Then, maybe add 1/8" holes until the water level stays even and doesn't gurgle?

Any help would be greatly appreciated. This is my last obstacle in completing this sump.


- Skins
Not enough air. I'd start with a very small 1/16" hole and keep enlarging it until you get good results.
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