Silent and Failsafe Overflow System
- Thread starter JohnL
- Start date
kudora
thread reader
here is a couple of pics of my beananimal overflow build thats still in progress
at this point its been drilled and the overflow is being siliconed
pic of after black acrylic has been siliconed to the front
pic of back painted back and black acrylic
at this point its been drilled and the overflow is being siliconed
pic of after black acrylic has been siliconed to the front
pic of back painted back and black acrylic
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BeanAnimal
Premium Member
There is tremendous gas exchange due to the calfo overflow. Even without a large overflow, if you have proper surface agitation from powerheads or closed loops, then you have sufficient gas exhange in all but the most extreme environments.
Reefski's
Active member
as the water flows over the overflow it is aerated. Eric Borneman did an article some time ago on RC that showed that skimmers do not add much if anything to aeration contrary to popular belief as long as you have overflows and powerheads. it is not the bubbles of the skimmer that adds oxygen very much but the surface contact with the water.
Carl
Carl
BeanAnimal
Premium Member
Exactly 
My tank is already drilled with three holes on each end inside the overflows. The bulkheads that are installed in these holes are 3/4" threaded. Now, I can CLEARLY create the triple standpipes at a 3/4" diameter. The question is if it will work well enough to do the job. Again, I would have two sets of three standpipes on each end of the aquarium.
The total flow through the rectangular weirs in the walls of each overflow will be between 612 gph and 943.65 gph. (This is not a guess, I had a fluids engineer do the calculation!) Will the two standpipes on each end clear that kind of flow without the third standpipe kicking in? Would they handle more volume if I modified the overflow walls to allow more flow? (There is a 1/4" gap between the top of the overflow wall and the ceiling of the tank, but filling that with water would be asking for REAL overflow I fear. I would either add more rectangular weirs or widen some of them to increase flow.)
Thoughts?
The total flow through the rectangular weirs in the walls of each overflow will be between 612 gph and 943.65 gph. (This is not a guess, I had a fluids engineer do the calculation!) Will the two standpipes on each end clear that kind of flow without the third standpipe kicking in? Would they handle more volume if I modified the overflow walls to allow more flow? (There is a 1/4" gap between the top of the overflow wall and the ceiling of the tank, but filling that with water would be asking for REAL overflow I fear. I would either add more rectangular weirs or widen some of them to increase flow.)
Thoughts?
I converted one of my pre-drilled return lines (I think 3/4 is pretty standard for the return lines in RR tanks) and it has pretty crappy performance as my full-siphon line. I am not sure if my experience is in line with anyone else but so far you have one thumbs-down experience on the 3/4. I actually used 1" piping but the bulkhead at the bottom of the RR tank is only 3/4 so that is a bottleneck.
Weir flow calculation
Weir flow calculation
No! That would be like saying that the volume of flow through a funnel is the same as what you can pour int the funnel! The weirs are the rectangular cuts in the wall of the overflow - in case that term isn't understood. Each of those rectangular openings can handle only a certain amount of flow passing through it any a given time before it is "full". The rate of flow through the weir is determined by the size of the weir and the amount of head applying pressure to the liquid flowing through it and the thickness of the wall the weir is cut into and the viscosity of the liquid and the material the wall is constructed out of. All these factors will cause a friction or a change in the pressure on the liquid to make its passage through the weir more or less difficult and thus affect the flow volume.
SO, if I pump more than 943.65 gph through the return lines, I will exceed the capacity of my overflow to accept the overflow and will flood the room until I run out of water to pump into the tank. In my case, until the sump runs out of water which is about 100 gallons.
Make sense?
Weir flow calculation
No! That would be like saying that the volume of flow through a funnel is the same as what you can pour int the funnel! The weirs are the rectangular cuts in the wall of the overflow - in case that term isn't understood. Each of those rectangular openings can handle only a certain amount of flow passing through it any a given time before it is "full". The rate of flow through the weir is determined by the size of the weir and the amount of head applying pressure to the liquid flowing through it and the thickness of the wall the weir is cut into and the viscosity of the liquid and the material the wall is constructed out of. All these factors will cause a friction or a change in the pressure on the liquid to make its passage through the weir more or less difficult and thus affect the flow volume.
SO, if I pump more than 943.65 gph through the return lines, I will exceed the capacity of my overflow to accept the overflow and will flood the room until I run out of water to pump into the tank. In my case, until the sump runs out of water which is about 100 gallons.
Make sense?
BeanAnimal
Premium Member
Re: Weir flow calculation
Re: Weir flow calculation
Only if the weir extends to the rim of the tank. If the weir is lower than the rim of the tank, then when flow capacity of the teeth is exceeded, the water will rise above the teeth and still flow into the box. The limiting factor will be the capacity of the standpipes themselves.
So lets extrapolate your situation a bit further. You have been told that the teeth in your overflow can handle X gallons of flow, before their flow capacity is exceeded. Let me remind you that at anything approaching the maximum flow, you will have one very turbulent and noisy waterfall created by all of those teeth, defeating much of the purpose of this system....
You also indicate that you have (2) isolated boxes to house the standpipes. This may work, but even though water seeks its own level, you can not guarantee that both boxes will always get the exact same amount of flow. It may be hard to keep them both in tune! The siphon standpipes will be isolated at the intakes, but interact at the sump level. You may see the water levels oscillate between the two boxes.
Re: Weir flow calculation
Only if the weir extends to the rim of the tank. If the weir is lower than the rim of the tank, then when flow capacity of the teeth is exceeded, the water will rise above the teeth and still flow into the box. The limiting factor will be the capacity of the standpipes themselves.
So lets extrapolate your situation a bit further. You have been told that the teeth in your overflow can handle X gallons of flow, before their flow capacity is exceeded. Let me remind you that at anything approaching the maximum flow, you will have one very turbulent and noisy waterfall created by all of those teeth, defeating much of the purpose of this system....
You also indicate that you have (2) isolated boxes to house the standpipes. This may work, but even though water seeks its own level, you can not guarantee that both boxes will always get the exact same amount of flow. It may be hard to keep them both in tune! The siphon standpipes will be isolated at the intakes, but interact at the sump level. You may see the water levels oscillate between the two boxes.
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