Durso drain question


Reefing newb
So my tank has been up and in good shape for a little over 18 months now. I've had a few issues, as most do with new tanks, but so far its been good. Last night I noticed a small problem. The drain back from the tank was very light. Not much volume. So I checked things out an saw that my return pump needed a good cleaning. After cleaning it the flow returned to normal. (Its been about 6 months since I last cleaned it.)

This morning I noticed my drain is making a sucking/bubbling sound. Not the normal flushing sound that these drains are known for but a loud sucking sound. Upon closer inspection I see that it too needs to be cleaned. I guess I should have asked sooner, since I've never cleaned it, how do I clean it? What keeps all of the water from draining back and out of the DT and flooding my sump/stand/floor if I pull it out?

Any help is appreciated!
If you shut your return pump off will your sump overflow? If not, shut it down, and pull the Durso and clean it. If it will over flow, wait until you are in the middle of your next water change. Pull out your used water, then pull the Durso and clean it. Put it back, and re-fill the tank/sump with fresh salt water.
Figured I follow up on this.

So I pulled the durso drain. Nearly overflowed the sump, but didn't. Next time I'll read and follow advice a little better. I'll wait until I pump out the sump for a WC!

Anyway, I pulled it and cleaned it. Lots of crusty stuff on and around the slits. Works great again and it quiet. It did cause something of a sand storm in my sump though. There is some sand in the overflow box area so it sucked some of it down into the sump. Not too big of a deal. I pumped out 20 gallons from the sump into 5 gallon buckets, then pumped it right back in through a filter sock.

My only issue is my skimmer. I kicked up some cheato pieces and they float around and get sucked up into the skimmer pump. Seems every day I'm pulling the whole skimmer out and cleaning its pump.