need plumbing advice

s2k

Active member
I am installing a Durso for a new tank and it sounds like a toilet flushing every 5-6 seconds so I think the hole on the end cap is too small. I made it bigger, but it still makes noise.

Then I realize the drain is under the water level in the sump. Should the drain be above the water level to reduce any back pressure. Any advice would be appreciated..
 

DRC69

Oh Well
Well it nice if the outlet is vented but not always necessary.
The key is the hole on-top of the inlet.
And yes the outlet should be above the water-line.
 

Hawkdl2

Mad Scientist
There are two general approaches to the design of overflows: air dependent and full siphon. Durso, Stockman, etc. all require air and will fluctuate between a full siphon and air infused turbulent flow if they are air deprived resulting in the flushing sound you hear. A well tuned air-dependent system (i.e. Durso) will be very quite, but never silent. If your system flushes you need to allow more air into the top of the system. The more air you let in, however the noisier the system gets from the inrush of air and the flow of turbulent water. One approach to solve this is to just keep drilling holes until the flushing goes away and as along as the system continues to become quieter. After a point it will start making more air noise (not flushing) and you simply tape over a few holes and you're dialed in. Installing an adjustable air valve (e.g. John Guest fitting) makes dialing in easier in some, but not all, cases. Also, many have found that 1 1/4" pipe to the bulkhead is the minimum diameter for an effective and most quite Durso/Stockman system.

The outlet can be above or below the water level, but the air in the system must be allowed to escape and the further under water the outlet is located, the more back pressure there will be in the system and the more the air will build up in the the outlet line, resulting in increased burping in the sump. An outlet above water eliminates most burping, but typically results in more splashing and salt creep in the sump. Often the best location is just an inch or so underwater - this reduces splashing from the outlet and minimizes the burping. On occasion, I've found drilling a 1/4" hole in the side of the outlet just above the water level allows enough air out without splashing to reduce burping to a manageable level.

I, and many others, have moved away completely from the air dependent approach and have gone with a full siphon overflow. The main advantage is it is absolutely dead quite - zero noise, because there is no air in the system so the flow in the line is laminar and there is no burping in the sump because there is no air in the water. Several people have described full siphon systems and been given credit for various manifestations of the concept, BeanAnimal most recently, as well as others, but they are not new and have been around for a long time. They do require initial tuning which is accomplished with a ball valve, or preferably a gate valve, near the outlet to adjust the flow rate to be equal to the return pump volume. Full siphons can move more water than air dependent systems so they almost always have to be dialed back.

Both system really should have an emergency overflow which is just another stand pipe extending an inch or so above the desired tank water level.
 

s2k

Active member
Larry, thanks for the in-depth response. I will cut the drain pipe alittle shorter and perhaps try a 1/4 inch hole on the side.

Can you also elaborate of full siphon overflow? Does this mean you do not have an endcap of the top of the durso for air to release and add a value to the drain? Thanks
 

s2k

Active member
My drain is also 1.5" so not sure if that makes a difference compared to the 1" drain.
 

805reef

New member
+1 on great writeup
i dialed back the flow on my drain using a ball valve, but i am interested in how it would be if i cut the drain pipe a little shorter. right now i have it going all the way to the bottom of the sump with flex pipe
 

OC CJ

Crushed coral > sand
I had this same issue when I plumbed my first tank. I learned that if your durso is the same size or smaller diameter pvc then your drain line, this will happen. I always make the durso at least 1/4" bigger than the drain line to prevent this from happening. My drain is about an inch under water even and i have no issues.
 

Hawkdl2

Mad Scientist
<a href=showthread.php?s=&postid=15449764#post15449764 target=_blank>Originally posted</a> by s2k
Larry, thanks for the in-depth response. I will cut the drain pipe alittle shorter and perhaps try a 1/4 inch hole on the side.

Can you also elaborate of full siphon overflow? Does this mean you do not have an endcap of the top of the durso for air to release and add a value to the drain? Thanks

Just the opposite - a full siphon system has an airtight end cap with no holes at all. Try it and see what happens- just replace the end cap with one with no holes and don't worry about it being completely air tight. If you try it, make sure you have the sump capacity for the amount of water in your tank between its normal level and the bottom of the Durso intake because it will siphon fairly quickly if you don't have a valve to dial it back. Once it get's that low the siphon will break until the pump catches back up. If you like the way it works (virtually silent), just glue the end cap on, or use pipe tape, and add a valve by the sump. I adjust the bottom of the intake level to not be so low that a pump failure would result in a flood in the sump. The "Bean" system uses a third pipe that is in essence an emergency overflow, but adjusts its height so it is very close to the water level you want and assumes most systems will have some amount of water flowing through it - which adds noise that I do not like. He then has a third overflow line he considers the real "emergency" overflow. He considers the system as he diesnged ti to be "fail safe" and I would say it is, but I don't buy the need for three pipes and believe you can easily dial in the flow to use just the main "Durso" overflow and use the second one as a more than adequate emergency overflow.
 

s2k

Active member
ok, thanks again for the explanation.
I'll give it a shot tonight. I'll try the full siphon method and will add a ball valve to my return pump to control the flow.

I wish I had a second hole drilled for the drain to setup an emergency overflow, but hopefully nothing gets stuck in the pipe.
 

s2k

Active member
I did the full siphon thing with the ball valve and it works like a charm. The only downside is that I had to close the valve to a point where the return flow is really weak. So I am planning to add another powerhead in exchange for the silent overlow.

Thanks again Larry. Much appreciated!
 

Hawkdl2

Mad Scientist
Then you probably don't have it dialed in correctly. The only reason to dial it back is to allow the return pump to keep up. You should be able to run your return full throttle. You dial back the siphon only to the point where the water level stays where you want it. This can be a bit tricky without a gate valve, but I've also been successful with just a ball valve.

Now, if your return pump is simply inadequate for your tank, that's a different matter.
 
Top