Do larger gravel siphons suck up water faster than smaller ones?

[finnfinnfriend]

I was just wondering because one that is rated for a larger tank than what I have looks like the perfect size to me, but if it sucks up water too fast then there's no point...I am talking about a plain old gravel siphon with no hand pump.

[shellieca]

Yes it will.

[finnfinnfriend]

How does it do that? The airline tubing is the same size on all of them.

[Aoicat]

Without getting into the details of fluid dynamics and such, the flowrate of a siphon is mainly determined by two factors. The interior diameter of the tube and the difference in height between the upper tank and the tube discharge. In this case the change in height is probably not a factor because you're not going to raise the tank or lower the floor enough to alter the equation significantly. So the deciding factor on how fast the siphon drains your tank is the diameter of the tubing at the smallest point. The bigger the tube, the faster you'll drain your tank.

[finnfinnfriend]

Are you talking about the rigid tubing or the flexible tubing part?

[shellieca]

Originally Posted by finnfinnfriend

How does it do that? The airline tubing is the same size on all of them.

I have 3 different sized syphon/vacs with different sized everything (vac tube/airline tubing), granted mine all have hand pumps to get them started but the principal is the same. When I use a larger sized syphon/vac in my 5.5g the 50% water is removed before I can vac the whole tank. I switched to the smaller syphon/vac & I don't have that problem. I don't know specifically what you are looking at but it seems odd the airline tubing would be the same size on the different sized syphon/vacs.

[finnfinnfriend]

Well I think it is...maybe not. Do you use the Aqueon ones? I'm thinking of the Aqueon ones.

[shellieca]

No Top Fin.

[Aoicat]

I'm talking about the flexible tubing. It doesn't matter how big the vacuum part is, the water can only travel so fast through a siphon tube. That speed is determined by the diameter of the tubing.

[Virto]

Originally Posted by Aoicat

I'm talking about the flexible tubing. It doesn't matter how big the vacuum part is, the water can only travel so fast through a siphon tube. That speed is determined by the diameter of the tubing.

Exactly.

I've found that most brands use the same size of tubing for various sized siphon ends. I typically use the largest they have for sale at the time, but I do prefer the smallest hard-plastic portion (diameter-wise) that I can find. It makes it easier to poke around some decorations without rooting up plants or making a big cloud.

If you're just trying to drain the tank but not vacuum the bottom, you can use any piece of tubing or hose, but you'll probably have to suck on the end of it to start the flow.