Wier Overflow Questions - Closed loop

[Gerryd]

Hi all,

Most likely stupid questions, but here goes.

I have a closed loop using twin overflows. Based on how I control the flow through my plumbing system, I can make it so the wiers always are filled so there is no waterfall effect or noise.

If I ADJUST the valves a certain way, I get more flow in the tank, but the water level inside the wiers grows smaller, more waterfall and noise.

I can add more water to the tank and that will fill the wiers a little, but they are still unbalanced. One side decreases more than the other, but they both reduce the water level.

BTW, the same thing occured when I had a sump and wet/dry and opened the pump valve too much as I always oversize/throttle my pumps.

Questions:

1. Does this indicate that I am flowing out MORE water than I am taking in and that I am now out of balance in terms of inlet and outlet water volume?

2. If I were to remove the wiers entirely, would this issue still exist? Or if I were to widen the grates somehow? Are the walls now preventing enough water from filling the wiers?

3. Am I really getting more flow out of the pump, or just DIVERTING it from somewhere else in the system?

I just want to ensure I am not missing something in my reasoning....

Appreciate any thoughts.

 

[shoggoth43]

If you think of your weir as a dam, which it essentially is, if you place a board across a stream you will have some amount of water flow across the top of it. If you do the same with a faster flowing stream, the amount of water flowing across the top of it will be "thicker"/deeper because you have much more water to move from the upside to the low side.

This is happening in your tank, but since you have a closed loop you don't have an infinite amount of water on the upside. For more flow, you need that "thicker" overflow layer and more water in the tank. The only place to get it is on the low side of the wier, which drops the water level in your overflows.
You could remove the wiers and you won't have this issue. You could also try filling the overflows a bit more and deal with a larger amount of water in the system. You could also try cutting larger teeth into the overflow or remove them entirely and see if that helps any. I would keep the weirs just from an aesthetic point of view and the surface clearing they provide, but if you're getting noise you're definitely outgassing CO2 so it's worth doing something about it.

Hopefully I explained that in a way that makes sense.

-
S

 

[Gerryd]

S,

What you say makes perfect sense..The dam analogy is a good one.

So..you confirmed what I thought and your suggestions, pros, and cons are all similar to mine as well

I also like the skimming and I need the MAJORITY of the wier wall to hide the plumbing within them so I will not remove the wiers.

But, I want to use more of the flow I have as well, as the adjustment made a big diff in the tank. I can deal with the c02 offgassing, but the noise it not good. Very quiet now and I want to keep that aspect...

1. Adding more water to the system. I did do this and it helped a bit, but how much water can I add? It seems I will always have to adjust this when I adjust flow. I don't like that connection.

2. Removing teeth, enlarging the space, gap, etc. I think this is where I will go first. I can open the gap a bit or make them wider and see if that helps. At worst, I can remove the top 1-2" and see what that does. Will still hide the plumbing and offer more flow, but will lose the skimming aspect.

Well, let me think about it..... Remember that I can adjust so all is balanced and no noise, but I know I am limited by the dams....

Tom suggested a long time ago to remove one of the wiers so I still have some skim. I can experiment on one side at first to guage the effect...... any increase will be a plus I think.

Thanks as always.

 

[shoggoth43]

Well, ultimately you can turn off the pump and fill the tank so that you have some amount of water over the top of the wiers. As long as when you turn the pump on you don't overflow the tank ( water still rises in the tank as it drops in the overflow ) you should be good. What brand of tank is it? I know some of them have a removable front plate that you could modify, or you could modify the bit behind the plate. I don't recall what brand it is but it does draw from the surface and subsurface as well. That may also be another option if you were to cut some additional holes in the wiers at a certain level.

-
S

 

[Gerryd]

S,

It is an all glass about 8-10 yrs old.

Teeth are at top and bottom of wier walls.

I need to brain on this for a bit.....

 

[Gerryd]

Ok,

Done thinking and experimenting

Each wier has a grate at the top with multiple 'teeth'. I simply opened the valves as I wanted and saw the one wier drain. The other does not seem to move as much even though the hookups seem the same.....

I removed one 'tooth' at a time from one wier and waited for the wier to fill a little more. It took 3.5 'teeth' to make up for the loss in the overflow that I gained in in-tank flow/current. This did not require any additional water, and that wier still skims for the most part as the extra gaps are small, but make a big difference.

So, just need a bit of sponge or something to cover the missing teeth. The fish won't make it past the intake strainers, but I don't want any fish in the wiers long term lol

Took 1-2 minutes total and I have more flow than before

NOW I am uprooting my tank, literally........I finally got how powerful this pump can be!!!

Update: After some time I opened the valves more and the other wier drained a bit, so I removed a 'bad tooth' from that side as well. All seems balanced and fine once again......I like it!

******************

On another note, while I was experimenting............

My outlets are as follows:

1. 1" outlet from outlet cone to tank. Basically from the pump to the tank direct.
2. 2x1" outlets from 3 parallel leg merge. Each of these two 1" outlets connect to 3/4 bulkhead/pvc pipe for the tank returns. Each 3/4 return has 3 loc-line outlets from the main 3/4 pipe. All loc-line is also 3/4.
3. One of the 1" leg outlets is split with a 1.5" WYE PRIOR to the 3/4 connection. The split from the wye goes 1" to the tank, and the other goes 1" to the 3/4 loc-line back to the tank.

I fully opened the valve to the 1" outlet I hooked up from the parallel outlet merge. . With the valve open, most of the flow from this outlet goes to the larger sized outlet rather than the 3/4 loclines.

I think this may be better as there is less head on this line than the other with the 3/4 reduction and then the 3 loc-line split at the end. These outlets now produce less flow, but it may not matter as the 1" is producing some heavy flow.

Also, the loc-line split was from when I had many areas to cover in mist. The new scape makes that less of an issue.

I think I may play with capping the 3/4 bulkhead returns and just use the 3 x 1" outlets and have them go over the wall. Two of them already do, so a third won't be bad.

I can then remove the visible loc-line from the tank. The over the wall outlets are mostly hidden by the new scaping. I would just need to run the other 1" leg outlet to the tank instead of the 3/4 bulkhead.........

I need to think about this. Decisions, decisions, lol

Thoughts are appreciated.

 

[Gerryd]

Hey,

I did reduce one of the loc-line splits from 3 outlets to 2 and reduced the length a bit and removed one of the Y splits. I noticed that there was barely any flow coming from 2 of the 3. When I made the change the second outlet now had some flow. The other outlet continues to get the majority. I think this reduces head, so I will leave as is.

The other side does have some flow from all 3, but 2 of them are not much. I will modify this set as per the first and see how that goes.

I cannot open the 'flow' valve more as this starts to affect the flow to the 3 legs and the mazzei.
So, that should be it as far as intake flow modifications I think I am at max capacity for the current configuration!!!!

The PSI on the legs has been reduced, so another bit of help......

Still, a nice gain, and only lost a few teeth in the process lol