Plumbing question...

[Dom]

I'm doing a build in which I will have (2) overflow boxes, each connected to 1" PVC.

I plan on a 1" PVC return which will split once inside the tank.

The problem is that the intended return pump outlet is only threaded 3/4".

Can I do a return that is only 3/4" PVC?

I suppose I can get a connector that goes from 3/4" to 1", but my concern is that the flow OUT will be greater than the flow IN.

The intended return pump has the capability to keep up with the overflow, but I am wondering about the 1/4" diameter difference in the return.

Feedback?
Dom

 

[Larry L]

Not exactly sure if this is what you're asking, but I think you are thinking about it backwards - it's the overflow that needs to keep up with the return pump, not the other way around. The only water that can overflow back to the sump is the water that the return pump is putting into in the tank - there's no way the overflow will send more water to the sump than the return pump is sending to the tank in the first place. In fact, you usually want your overflow plumbing to be oversized compared to your return, just to make sure that even if there is a small amount of clogging in the overflow, all the water sent to the tank still makes it down the overflow.

 

[Sierra_Bravo]

^ Larry beat me to it. You are fine using a 3/4" to 1" adapter on the return side, or even just staying at 3/4" if you were so inclined.

 

[redfishbluefish]

I would immediately step up the return to 1 inch....you'll have less headloss.

 

[jgvergo]

I would immediately step up the return to 1 inch....you'll have less headloss.

I'm pretty sure the head loss will increase if the return line increases in diameter. The pump has to push up a larger volume of water.

 

[redfishbluefish]

I'm pretty sure the head loss will increase if the return line increases in diameter. The pump has to push up a larger volume of water.

It might be counterintuitive, but larger pipe diameter lowers the frictional loss per volume of water, causing for greater flow. Go to any of the headloss calculators, pick any pump and some length of pipe and now look at two different diameters.....the smaller the pipe, the greater the headloss.

 

[doughboy]

you can look at it this way

1" cross section is roughly double 3/4" cross section area.
so if you push less water using 3/4", but you need to push twice as much compared to 1", so in effect, the 3/4" has to travel twice the distance of 1" to get the same volume, thus have to overcome twice the friction.

 

[Dom]

Not exactly sure if this is what you're asking, but I think you are thinking about it backwards - it's the overflow that needs to keep up with the return pump, not the other way around. The only water that can overflow back to the sump is the water that the return pump is putting into in the tank - there's no way the overflow will send more water to the sump than the return pump is sending to the tank in the first place. In fact, you usually want your overflow plumbing to be oversized compared to your return, just to make sure that even if there is a small amount of clogging in the overflow, all the water sent to the tank still makes it down the overflow.

That makes perfect sense to me; you can only remove at the rate at which water is returned to the display.

 

[jgvergo]

It might be counterintuitive, but larger pipe diameter lowers the frictional loss per volume of water, causing for greater flow. Go to any of the headloss calculators, pick any pump and some length of pipe and now look at two different diameters.....the smaller the pipe, the greater the headloss.

Sure enough... Live and learn!