Overflow keeps flushing

LeChef · May 14, 2021

Luckily I’m just water testing though it went bad the first time my overflow keeps flushing, it fills up and then drains causing a loud gurgling and I’m not sure how to fix it. My main siphon is currently just a bulkhead hole that the water goes down but I’m not sure how to fix this. I’ve tried filling the tank up a lot but that just fills my sump up to much, I’ve increased and decreased my return pump flow, I’ve also slowly closed the main siphon with a valve to see if that helps but it’s still doing it. Is there a special plumbing I’m supposed to use? Would love any ideas and fixes!

Brady4000 · May 14, 2021

Look up durso drain, this is what I did.

KrisReef · May 14, 2021

You have two drains, 1 is supposed to be the main and the other the emergency from what I can tell looking at your pictures.

When the drain is first starting to fill, water flow in until the pipe gets totally flooded. At that point, the water creates a siphon flow that sucks all the water down the pipe, making a nice whooshing sound that continues until the overflow cup is emptied and then the sucking sounds erupt as air goes into the return and the whole refill-suck cycle just repeats.

Couple of ways to attack this, one is to thread an airline tube down into the drain so that the siphon sucks air through the tube to prevent "the whoosh' from ever building up, (TRICKY TO BALANCE) -may not work?

The other place to impact the drain flow is to open up the emergency drain, leave them both open and see how that goes.

I have a similar 2 drain set up, the primary I installed a standpipe on to decrease the drop of water over the cup-teeth which reduce the waterfall noise... and the second is slowly pulling water also and it prevents a siphon from getting started in the number one drain.

Good luck.

KStatefan · May 14, 2021

I can not see the pictures but it sounds like you have two drains a full siphon and a emergency? Adjust the gate valve on the full siphon until there is just a small amount going down the open drain.

ca1ore · May 14, 2021

Flushing typically happens with a single open channel drain that is being asked to move too much water, so it cycles between operating as an open channel and a siphon. It can also happen with a Herbie-style drain, either because the gate valve on the siphon is open too much or because the emergency is being asked to do too much. Either way, its a calibration problem.