Noisy drain to sump

[Leon71]

I've researched lots here and other forums to find out how to stop the noisy drain in my new setup. Just some history.

I have a Marineland 120gal with a corner overflow. The plumbing came with the tank and is a type of durso system. I have 1" bulkead through the bottom of the tank, followed by 1.5" standpipe and two 90° elbows at the top. The one elbow has two 3/8"-1/2" holes (one on either side) just above the standpipe, and a vent tube at the top. I can't get it to stop sounding like a toilet drain. So I replaced the elbow with a tee and cap. This seems to be common practice, so I thought I would give it a try. The top is now pretty silent. On the bottom I have 1" PVC straight down from the bulkead to the sump. With a union inline.

Now the problem. On both setups, I have extreme amounts of air coming down into the sump. I'm talking 2-3" high "boiling" in the sump. I've tried a shorter downtube (just at the water surface) and a longer downtube (3" off the bottom of sump, in 14" of water). There doesn't seem to be any change. Any help would be greatly appreciated. Am I overlooking something?

Thanks, Leon

[fishytime]

You said you capped off the top?.... If you did, you still need a vent hole.... Start off small and increase size til the gurgling stops

[Leon71]

Sorry, forgot to mention that I drilled a vent hole in the cap until the top became a lot quieter. Started out with 1/16" hole. Kept going until I had 2 holes at 1/8" and two at 3/16". Did I move too fast? Am I letting in too much air now? It seemed that until I had this many holes, that as soon as I put the cap on the overflow, it wanted to overfill the corner.

[Lampshade]

What i did to allow some "adjustment" was drill 3 x 1/4" holes through the side of the cap into the pipe it sat on. I didn't seal the cap on to the pipe, and could twist it to open/close the holes. worked out great until I put a high flow pump for my return, lots of microbubbles in the duroso set-up.

[Leon71]

I am using a plug, but that would work for adjustment as well. Will try that. Thanks. So if I get the setting up top right, will that cure the bubbles down in the sump? These are not microbubbles, but rather huge boiling effect.

[e46er]

Pipe running straight dOwn into sump will be impossible to get quiet with a durso standpipe

[paddyob]

Originally Posted by fishytime

You said you capped off the top?.... If you did, you still need a vent hole.... Start off small and increase size til the gurgling stops

Better yet... drill a 1/8 hole in the cap and add an airline valve. My drain is almost completely silent. If it bubbles I simply adjust the airline valve.

Here's a pic of mine.