stupid plumbing question

[SpeshulEd]

If my lockline in the tank is 3/4" (I think) it's probably worthless to put larger plumbing going to it, since it'll be bottlenecked at the lockline, right?

Or would I gain more flow/gph from larger plumbing before the bulkheads?

My pump is 5800gph, but I don't think I'm even coming close to that because of the smaller plumbing. I'd like to redo some things to make it look nicer under the tank, but don't know if larger plumbing would be a benefit.

 

[john73738]

Not an expert but yea I believe that the bulkheads are going to "throttle" your flow.

 

[Toby_H]

Not an expert but yea I believe that the bulkheads are going to "throttle" your flow.

Even though he's not an expert, he is exactly right...

 

[SpeshulEd]

Thats what I figured. Thanks guys.

Well, I guess I can still clean things up a bit. I'm not ready to redo all of that yet.

 

[Toby_H]

I've thought a little more about this and now I'm less sure of my immediate response...


Let me create a hypothetical situation that slightly exagerates your situation to help explore a point...

If we have a 1" (ID) bulkhead in the bottom of a tank, 1" (ID) pipe going up and a 1" (ID) pipe going down... If you have at least the minimum verticle drop of 9' you will have 600 gph of flow through the pipe (according to Chompers very helpful sticky in the DIY folder).


But if we increase the diameter of the pipe below the bulkhead... the weight of the water in the pipe will increase, thus increasing the rate at which it falls. If the water falls faster the negative pressure (suction) at the bulkhead will increase, thus increasing the flow rate at the bulkhead...

Analyzing the physics invovled this would in fact increase the flow rate, although I have no idea how much it would increase the flow rate. It will likely be such a small effect it's not worth it for conventenal aquarium filters.


Any engineers or physics geeks care to share their thuoghts?

 

[SpeshulEd]

Hmm...well, I guess if the goal is to clean it up under the tank, cleaning it up with larger plumbing wouldn't necessarily be a bad thing. Right now I'm using 1" (ID) soft plumbing. The pump has 1.5" intake and discharge. Using the larger plumbing, certainly wouldn't hurt.

 

[CHOMPERS]

Toby has the right idea/concept. The flow loss is accumulative throughout the whole system; it is the sum total of all losses. If you can remove some losses, the end result will be better performance.

Restriction vs. flow rate is not linear. Higher velocities cause exponentially higher restriction, especially at the fittings. Lower velocities cause exceedingly lower restriction. Increasing the diameter where you can will therefor reduce the restriction.

My concern is the loc-line. It tends to have higher resistance due to the ribs inside. Increase the number of lengths of it so that it isn't the bottle neck (add enough so that the cross sectional area off all of the loc-lines add up to or exceed the area of the main plumbing).

 

[SpeshulEd]

Excellent.

Just to make sure I'm getting this right...I should keep the loc-line long as oppose to short to stop the bottle necking.

Right now I have the loc-line on both sides of the tank. It comes up roughly 10" and splits to two lines, both around 20", one side of the y, goes to the top of the tank, the other goes to the side to shoot detritus out of the corners.

Not the best photo, but here you can see the loc-line, especially the one on the right.

I'd be better off keeping it long like that, rather than shortening it?

Sounds like I'll be running 1.5" ID plumbing from the pump to a y. The Y will split the plumbing to both returns and I'll reduce it right before I get to the bulkhead.

 

[boldtogether]

IF you have 1.5" pipe from the discharge side of the pump and split it as close to its final destination as possible into two 3/4" pipes, unrestricted, the pump theoretically would still be pumping through one 1.5" pipe. Even if you split that 1.5" four ways as long as all the diameters added up to 1.5", or close to it.

 

[CHOMPERS]

Just to make sure I'm getting this right...I should keep the loc-line long as oppose to short to stop the bottle necking.

No, that's backwards. You want them to be as short as possible, and you need more of them to reduce the restriction. Or split the water with another return method such as a spray bar.




(I'm selling a fish on Craigslist and dealing with some idiot tire kickers. If my grumpiness is apparent, it is not intended and I apologize in advance.)