Overflow Questions

[redracer77]

I am having a tank made soon and want to get sort out an overflow design soon. I have been looking on the net and finding varying designs.

Tank will be 1500x700x600

I am wanting it to be quiet, (it will be in the living room) and reliable.

The sump will be in the next room (Davidr inspired) more questions to come on this

Is a stand pipe with a weir the best option?

Any suggestions?

[hovmoller]

A "Herbie" overflow is what I did on my 800L tank.

It is completely silent. I thoroughly recommend doing it this way.

These are 25mm fittings.. will easily cope with 4000L/hr

[David R]

*snap* we must have been writing the same thing at the same time... :-?

A Herbie or Bean Animal type set up [google it] is the best bet for silence. Basically you have two or three drains, all capable of handling nearly the full amount of flow from the pump, one is set lower than the others and controlled with a ball valve to run at a full siphon, taking say 90-95% of the flow, and the remaining drain(s) handle what is left and are also near-silent because of the small amount of water flowing through them leaving an unbroken air column.

The design of the weir/overflow itself will depend on where the tank is and how you want it to look. I went with a traditional corner box as I didn't have space for an external, but if you can work it then an external box is the way to go, similar to this old tank of mine (now Hovmollers cold water marine tank);

I found this thread on MFK a useful guide useful when figuring out how big to make my drains; http://www.monsterfishkeepers.com/forum ... Viewing%29

*edit*

I'm running two 50mm drains and around 8500-9000LPH at a conservative estimate. With the ball valve on the lower drain wide open it runs as a full siphon, just. I have the ball valve slightly closed and run a little water down the higher drain, so IMO the MFK numbers are pretty much bang on. Given that a 25mm pipe has less than a third the cross section of a 50mm pipe I'm not so sure a 25mm drain could flow nearly half of what a 50mm one will handle?

[redracer77]

*snap* we must have been writing the same thing at the same time... :-?

A Herbie or Bean Animal type set up [google it] is the best bet for silence. Basically you have two or three drains, all capable of handling nearly the full amount of flow from the pump, one is set lower than the others and controlled with a ball valve to run at a full siphon, taking say 90-95% of the flow, and the remaining drain(s) handle what is left and are also near-silent because of the small amount of water flowing through them leaving an unbroken air column.

This is probably the simplest explanation of this I have found - Thanks

Does having an overflow like this still collect most of the detritus?

Is there anyway of having a pickup/intake near the bottom of the tank?

[hovmoller]

Given that a 25mm pipe has less than a third the cross section of a 50mm pipe I'm not so sure a 25mm drain could flow nearly half of what a 50mm one will handle?

All I know is that if I am to believe the graph on the box of my pump it delivers around 4000lph at the head height I have and on my 25mm outlet line I have to close the ball valve slightly so it takes 99% of flow. I have not compared that to the MFK numbers.

Does having an overflow like this still collect most of the detritus?

You will need enough flow around the tank to suspend crap into the water so it can get removed at the overflow at the surface (harder to achieve than if you have pickup at the bottom but not impossible

Is there anyway of having a pickup/intake near the bottom of the tank?

In theory yes but you would need an area in front of the overflow to be separated from the rest of the tank with a pipe going to the bottom. This way it would draw water from near the bottom and go up and over the overflow. I am thinking of including this in future setups but haven't really worked out a good design for it yet.

[redracer77]

In theory yes but you would need an area in front of the overflow to be separated from the rest of the tank with a pipe going to the bottom. This way it would draw water from near the bottom and go up and over the overflow. I am thinking of including this in future setups but haven't really worked out a good design for it yet.

Would something like a baffle in a sump work for this? possibly made from acrylic with slots near that bottom, and the top being slightly higher than the overflow height. I will try to draw what I am thinking.

[David R]

I've often pondered having a lower pick up, but I've always found it simpler and tidier just to have a well aimed return or powerhead to keep the debris circulating. I do get a bit of a build up of waste in front of the stump in my new tank, but it just happens to be one of the main areas the big royals hang out so they often give it a stir which helps send it up and over the weir. To me, having the surface skimmed is more of an advantage than the downside of it being a little more difficult to pick up waste off the bottom of the tank.

[hovmoller]

I started thinking about this after your question and I have thought of a super simple way to do it (at least with my setup).

If you look at my above drawings I would drill a hole through the bottom of the overflow box. Install a bulkhead (tank fitting) in it and a pipe almost to the bottom of the tank. Then adjust the male bit of the tank fitting to be same height as overflow (or thereabouts, can be adjusted).

This way water will still go over the overflow and skim the surface but at the same time you will be able to decide how much of the water is pushed up through the pipe from near the bottom.

I will go draw it. Much easier to understand a picture.

[hovmoller]

So here's my solution...

Quite simple but will work in my situation. (the shown pipe is an addition to the already working system shown earlier)

This way I can regulate how much water I want coming up through the pipe while at the same time water will still go over the overflow.

[David R]

So that pipe drains out the back, or somewhere? I presume there's an opening somewhere near the top to prevent it siphoning the whole tank! Looks like a very simple and elegant solution, and another positive aspect for the overflow box vs a full-height overflow.

[blueether]

just pulls water from the bottom of the tank into the overflow box where it drains via a beananimal overflow?

Sort of make sense to me anyway

[David R]

Ah, yep, got it now! I guess the size of the pipe would determine how much water it sucks up? Only potential downfall I can see would be that it could cause more water to siphon down into the sump when the pump switches off, depending on how far below the height of the weir your drains are.

[hovmoller]

Yep bluether got it. It simply spills out water into the overflow box. If it is set to the same level as your overflow then it acts exactly like the overflow itself and water should pour out over the edge of the pipe similarly to how it flows over the overflow.

If the pipe is lowered a bit though then I suspect the flow would increase a lot because of the level difference but yes you are right David in the case power is off tank would now drain down to the level of this pipe instead of the overflow so would need to make sure there is room in the sump to cope.

In my mind this seems to work and could be the "best of both worlds" with both surface skimming and bottom extraction. I will definitely try this one day

[David R]

I'll certainly be interested to see how it goes if you do, sounds like a good idea especially with the internal box like yours. I'm sure you could make it work with a full height overflow some how though.

[redracer77]

This looks like something I imagined. I guess if I get the box drilled for this I could block it off later if it doesn't work as expected.

I will consult the tank maker about it. Thanks