Problems with Durso Standpipe

[Itchy Trigger]

I've just set up a 270g tank, which is drilled in the bottom - two 1.5" drains, two 1" returns. Plumbed to a LifeReef sump. I've got Durso standpipes on the drains, and I'm still getting a lot of noise.

I started by drilling a 1/16" hole in the end cap of the Dursos, but the water level in the overflow boxes dropped low, and I got the awful loud sucking sound. So I drilled the holes bigger, and the water level came up. But I still have a sucking gurgling noise coming through the holes in the tops of the Dursos. The bigger I drill the holes, the higher the water level gets in the overflows, but the louder the sucking noise gets.

Please help. The tank is in the living room, and I was hoping it would be MUCH less noisy than this.
Itchy

 

[Shabadoo]

How much flow do you have going through your Dursos?

My experience is that a pair of 1.25" Dursos can handle about 800G/H quietly (definition of "quiet" may vary.) I run 600G/H silently, but with 2x1.5" Dursos you should have greater capacity. I would install a ball valve, or true union, on the return and reduce the flow until they settle down.

Also more than a 1/4" hole is not necessary, so you shouldn't need to drill a larger hole in the cap.

-Scratchy

 

[shawnz28]

How high is the water level on the T and 90 on the durso? Is it half way yet?

 

[Itchy Trigger]

Shabadoo - I've got about 1200 gph total (with two drains/two returns). I do have ball valves on the lines, so I'll try slowing the flow a little - thanks.

shawnz28 - the water level is above the T & 90 elbow by about 1/2".

 

[shawnz28]

sounds like the holes are too big now. The water level should be half way up the T try to slow down the return a touch.

 

[kim]

I don't have Durso's (no need, a bit of airline does the same thing) but I think I understand the dynamics. You have good advice so far. To explain.

First, I am presuming that your noise arises when the water level in your overflow drops below the water inlet in the Durso ? That'll cause a waterfall over the weir, but more important, gurgling and flushing in the pipe ? If this is correct, read on. Otherwise, I have misread the situation.

Your water is dropping too low because your downpipe's capacity exceeds the return pump's capacity. Congratulations. The reverse is really really bad. This is good.

But because of this, water inside your overflow is dropping until the water inlet of your Durso is exposed. Then air rushes in, and that reduces the amount of water that can flow, effectively throtting back the pipe. Water then rises. Water then falls. Errrr....repeat.. Noisy.

Increasing the hole at the top of your Durso will add more air to the flow, so will reduce the mismatch between pipe and pump capacity. But when it gets too big, you no longer have a Durso, you have (effectively) an open pipe. If you use air to "stifle" your downpipe, it will be noisy. The airhole is meant just to regulate (ie smooth out) the flow of air.

You need to put a ball valve in your standpipe and reduce its capacity. And keep the Durso airhole small. Ideally make it so that the Durso airhole will be covered if the water rises too much. Eg snail in pipe reduces water flow more than you intended.

If you do this, the "air regulated" flow will automatically convert to a siphon when the Durso is submerged, increasing flow to the maximum possible, and possibly saving your floor. Then it will be noisy again but you may be happy for it !

kim