DIY durso issues

Salty Rambler · Dec 28, 2021

A few years ago I built a DIY durso and weir for my undrilled tank. When I reassembled it and started it up after its most recent cleaning soak, it started the "toilet flushing" sound I've read about on the forums but hadn't experienced myself until now. The water levels are holding steady. I've read that sometimes the flushing sound is caused by the return pump not being in synch with the volume of water going through the overflow/durso, but I assume if that were the cause, the water levels would also be fluctuating. Is my assumption incorrect?

The durso is glued PVC that runs up the inside of the tank, over the lip, and back down the outside of the tank. When it reaches the tank stand, it transitions to a clear hose that slopes it into the sump. The hose ends a few inches under the water line in the sump. The return pump is a clear hose leading from the sump, transitioning to glued PVC to run up the height of the tank and over the edge into the DT. I control the flow with a ball valve on the PVC portion of the return pump plumbing. I originally thought I might have accidentally bumped the ball valve slightly during cleaning, but again, I assume that would have resulted in unstable water levels, vice the (noisy) stability I'm currently experiencing. Welcome any/all advice to banish the flushing noise.

shwareefer · Dec 29, 2021

I don't have a durso but the flushing is caused by the pipe going from full siphon to air in the pipe over and over. I'm guessing from your description you have no drain control so the adjustment has to be on your return flow - more flow to stay at full siphon, less flow to stay at air in the pipe. Either will remove the flush. I think full siphon is safer to not lose siphon all together and have a flood and be quieter.

Billdogg · Dec 30, 2021

Your return pump is pushing more water into the tank than the drain can handle. On a really good day, a 1" DURSO can handle 350gph max. In reality, 250-300gph is a better flow rate for it. Put a ball or gate valve on the return line to slow it down a bit.

Salty Rambler · Dec 30, 2021

Billdogg said:
Your return pump is pushing more water into the tank than the drain can handle. On a really good day, a 1" DURSO can handle 350gph max. In reality, 250-300gph is a better flow rate for it. Put a ball or gate valve on the return line to slow it down a bit.

I have a ball valve on the return pump line and can slow it down. I hesitated to do so without further research though, because the water levels are holding steady, and I was hoping not to start the equalization dance again. I thought if the pump was pushing more water than the drain could handle, I would be seeing a slow rise in the water level in the DT leading to a flush to drop it back down, but maybe the flush is forcing the drain to constantly keep up, so I'm hearing the imbalance versus seeing it?