From Durso To Herbie

[Wavemode]

I have a 50 gallon SCA cube with all the stock plumbing. The tower has Durso drain approximately 1.5" and a return pipe approximately .5". I just upgraded my return pump to a bigger unit and am running an external .75" return up the back side. I want to turn the old Durso and return into a Herbie system to quiet my tank down but want to verify the larger of the two pipes (Durso side) should become the main drain and the old return should be the emergency overflow. I'm familiar with heights of tubes and how the Herbie drain system works. I just need to verify which one is which and if it will even work without re drilling for bigger bulkheads.

 

[recess62]

Usually the larger pipe is the emergency. You may have issues with the .5 inch main though

 

[Wavemode]

I was afraid you might say that. I'm curious if it could still work With the large tube as the main since you only have a slight trickle going down the emergency side. I realize the back up drain wouldn't be much help in an actual emergency but if you screen your main and cap your tower correctly it seems logical. Then again maybe a .5" main is enough to get 200-300 gph through the filter if you run it wide open all the time but that would make my 951 gph return pump a bit moot.

 

[TheEngineer]

Usually the larger pipe is the emergency. You may have issues with the .5 inch main though

This.

I have this same tank and run it this way. A siphon pulls way more water than an open pipe so don't worry about flow rates.

 

[Wavemode]

Perfect! That's exactly what I needed to hear. Thanks you guys for the valuable feedback!

 

[TheEngineer]

Just to make you feel even more comfortable... I did the math

A .5" drain running down 2 feet (I guesstimated) and submerged under water in the sump will flow 417gph at full siphon. This same setup, but with a 1" drain will run 1666gph at full siphon wayyyyyyy more than you need.

A 1" drain submerged 2" under the water's surface will run 418gph (1.5-2x your pump rate). (<- no siphon) The same switched to a 0.5" drain will run 120 gph, way too slow and you'll get a flood.

 

[Wavemode]

Wow that's great information. So the half inch drain 2" under the surface in the tower, with a gate valve, and submerged in the sump should be a good setup? Then the larger tube will make a great emergency drain. Do you think my return pipe being three quarter inch is too large?

 

[TheEngineer]

Wow that's great information. So the half inch drain 2" under the surface in the tower, with a gate valve, and submerged in the sump should be a good setup? Then the larger tube will make a great emergency drain. Do you think my return pipe being three quarter inch is too large?

It works for me. A 3/4" return is good. It drives two 1/2" nozzles so the extra volume won't go to waste.

 

[Wavemode]

Awesome! Looks like I'm all set. Thanks so much for all your help.

 

[Brew12]

@icecool2 nailed it. Full syphon drains flow a huge amount of water. It is not even comparable to a Durso.

Your return piping really can't be "too large". It just reduces pump head loss. That said, a 3/4" return will be capable of slightly more flow than your 1/2" drain so unless you are going for a crazy amount of flow through your sump your setup plan should be just fine.

 

[ReeferBob]

You don't need an emergency drain if properly designed.

 

[Wavemode]

That is a very thorough explanation for the confusion I was having. That video is awesome! I can easily convert my tank to make it whisper quiet. On the main drain what's the difference between having it hook like a Durso and leaving it straight with a cone screen top? Noise? From watching the video it looks like I can pretty much leave my Durso as is for the open drain. Maybe just increase the size of the hole in the top for equalization.

 

[TheEngineer]

You don't need an emergency drain if properly designed.

There is some good advice in this video, such as: design your sump to handle your tank's back flow, set your returns higher in the water and use unions on fixed plumbing. I'd caution against some of this other advice though.

Don't let running your pump dry be an acceptable state your system gets to if a drain gets plugged. At best it is bad practice and will shorten the life of your equipment and at worst you could burn your house down.

As far as having space in your DT to "absorb" the extra volume from your sump, this is a bad idea if you intend to use wavemakers, especially on a rimless tank. I run two in my tank and the water gets to within an inch of the rim. That's ~1.5 gallons of water before a flood and your return chamber holds 2 gallons. Half a gallon of water on the floor is a pain but water and electricity don't mix. Fire is a likely outcome. Also if you have an ATO there is even more water.

The video shows a tank with three emergency drains. One of those drains can handle the full flow of that return pump without a problem.

I think the intent was to show that a dual
overflow tank could be made into a dual herbie but it seems to be trying to sell more than that.

 

[TheEngineer]

That is a very thorough explanation for the confusion I was having. That video is awesome! I can easily convert my tank to make it whisper quiet. On the main drain what's the difference between having it hook like a Durso and leaving it straight with a cone screen top? Noise? From watching the video it looks like I can pretty much leave my Durso as is for the open drain. Maybe just increase the size of the hole in the top for equalization.

The hook on the siphon is helpful to get the inlet deeper in the water. Be careful with screens as they tend to get fouled and you'll find yourself spending a fair bit of time cleaning them and you'll have a hard time keeping your siphon tuned.

 

[Wavemode]

That's all really good advice that makes a lot of sense to me. It looks like I'll be able to convert my Durso to a Herbie fairly easily. Do I run two completely separate lines for the intake? The half inch main drain should have the Durso type hook on top but no drilled hole and it's the only intake line with a gate valve. Correct? The secondary larger pipe can be left as is for emergency. How far below the emergency drain should the main be 2-4 inches? Are both drain pipes under water in the sump?

 

[ReeferBob]

This video shows one example of what can be done for a full siphon style drain with the limited options out there using a tank with builtin overflows.

The point of the advice was not to let the pump run dry (or even have that as part of the disaster plan) but that if it should run low, it isn't the end of the world. In reality, it would not actually run dry it would simply cavitate when the water level was low enough that it couldn't return any back to the tank. Will this start a fire? That is very doubtful. Will it burn up the pump? Yes, eventually it probably will. Reduce its life? Probably. Will you ever run into a situation where your drain is 100% clogged? Very unlikely. Also keep in mind these are on GFI circuits and the pump itself is sitting in a pool of water.

You do want to run your drains underwater but not more than an inch or so. The reason the left drain was having trouble starting was when I made this video I had forgotten to trim the plumbing going underwater and it was literally like 6" under. That was enough back pressure to make the siphon hard to start.

Also with my return pump, I could have used the smaller of the 2 drains for the full siphon and the larger for the overflow. I hesitate to call one drain an "emergency" drain as it is needed in day to day operations to tune the drain. It isn't really possible to get and maintain a full siphon without some water overflowing into this drain. As you can see, it also it not set up to go fill siphon but could if I put the tubing on top and set the opening just above water level like Bean overflows do. This is a good idea. If I wasn't too lazy to redo the 4 standpipes in each overflow, I might just reverse them and make the smaller the full siphon.

You also want your open channel "trickle" drain above the level of the full siphon. In other words, the full siphon needs to run at full siphon and then raise the water up to the opening of the open channel. It doesn't matter how far above that full siphon it is though. You could have the full siphon way down at the bottom of the megaflow and the trickle way up at the top. The top open channel dictates the water level in the overflow chamber though. The lower it is , the more water that waterfalls over the edge and makes noise.

 

[Wavemode]

Thank you for all the extra information ReeferBob. What's the benifit of multiple gate valves? I appreciate your help.

 

[Robthorn]

I haven't read this whole thread yet but why do you need to change from durso which should already be very quiet. no tank will ever be dead silent. I have 90% of the people that see my ask me how my tank isnso quiet.
I run durso's. It is not dead silent. When I walk in my front door I want to know my tank is running. No flushing or gurgling, just running.

 

[TheEngineer]

Let's take these one at a time. Again, I think there is some sound advice in here, but it is mixed with poor practice.

This video shows one example of what can be done for a full siphon style drain with the limited options out there using a tank with builtin overflows.

Agree!

The point of the advice was not to let the pump run dry (or even have that as part of the disaster plan) but that if it should run low, it isn't the end of the world. In reality, it would not actually run dry it would simply cavitate when the water level was low enough that it couldn't return any back to the tank. Will this start a fire? That is very doubtful. Will it burn up the pump? Yes, eventually it probably will. Reduce its life? Probably. Will you ever run into a situation where your drain is 100% clogged? Very unlikely. Also keep in mind these are on GFI circuits and the pump itself is sitting in a pool of water.

And what happens when the water evaporates in the sump? The difference between sucking a little air and sucking just air is about 1/4". It depends on the return section, but that's about 1.25 cups of water in the SCA sump. I won't get into every nitty gritty detail here, this is just bad advice even as a fall back plan.

Also with my return pump, I could have used the smaller of the 2 drains for the full siphon and the larger for the overflow. I hesitate to call one drain an "emergency" drain as it is needed in day to day operations to tune the drain. It isn't really possible to get and maintain a full siphon without some water overflowing into this drain.

It is called an emergency drain because its job is to handle the full flow of the return pump should the primary drain become clogged. I refer to that situation as an emergency, but the name isn't important. If your second drain can't handle the full flow of your return pump, you can get a flood when the primary drain clogs. See my previous post about why having your DT "absorb" the extra volume from your sump is a bad idea. The second drain is not needed to tune the siphon, it is however part of the drain system. You can run your tank off of just one siphon if you were able to tune it perfectly and never have the lines foul. The second drain takes up any extra flow that your siphon isn't handling. As the water level in your sump changes due to evap the level in your tank will also change slightly. Rather than needing to constantly adjust your siphon, the second drain handles the difference.

You also want your open channel "trickle" drain above the level of the full siphon. In other words, the full siphon needs to run at full siphon and then raise the water up to the opening of the open channel. It doesn't matter how far above that full siphon it is though. You could have the full siphon way down at the bottom of the megaflow and the trickle way up at the top. The top open channel dictates the water level in the overflow chamber though. The lower it is , the more water that waterfalls over the edge and makes noise.

I agree, you want the second drain higher than the siphon. The difference in height between them represents the amount of water that can flux within the overflow your system can handle. If it is too small, you'll have a hard time finding that happy medium. Too big and you wind up draining a lot of extra water to your sump when the pump is off. That may not be a big deal if your sump is properly sized for the back flow.

 

[Wavemode]

It's so loud you can't even watch tv or have a conversation without raising your voice. It looks stock though and SCA claims the noise is classic Durso.