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Gravel/Water Siphons

562 Views 5 Replies 3 Participants Last post by  PlantedRich
I have an incredibly stupid question. Does anyone know whether the suction power of a gravel/water siphon increases with the diameter of the siphon? The reason I ask is I'm setting up a tank that has both a pool filter sand substrate area as well as a gravel substrate area (with dirt beneath the gravel). The dirt is of course dirtying up all the substrate as I plant, which I don't mind and knew would happen, but I'm trying to suction the dirt particles up to clean the sandy area, and my small siphon doesn't have quite enough power. I have to siphon into the sand about an inch which gets both it and the dirt moving. This is okay, but if I could siphon the area just above the dirt and get it to come up without shifting the sand too much, that would be ideal. Would a larger siphon work? (Mine is about 1" diameter.)

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According to Bernoulli equation, if the rate of flow is constant, the smaller the diameter, the higher the speed. ie higher suction.

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When cleaning my tank, I'm using a 5 mm hose to suck up all the algae and mulm on my sand. Then use a bigger hose to remove water. Why smaller diameter?
1. Can reach into tight space.
2. Water flow smaller which means I have longer time to clean my tank before suck out all required water.
3. Have more control compare with bigger diameter.

Just forget about my previous stupid answer, under gravity water speed will almost same given that the height difference is same.

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There are design ideas that make the difference in how the siphon will work. A larger tube to carry the water away will let more water go out so it does make it seem stronger. But at the same time running the same diameter all the way from end to end like just straight tubing will not work as well for many of us as what we see on the ready made units that have an extra large portion at the pickup end. What I find best is having the large area and holding it just above the substrate. This will pick up the loose stuff as well as some of the sand. But the large area lets the sand swirl around and drop back while the light dirt portion goes on out. Kind of self sorting the debris? If you use a larger diameter tube, you will get more volume flow but that can also mean you pour a bunch of the substrate out in the yard or drain.
To get the most "power" one might want to use a small tube at the pickup and larger from there on but most would not like that as it tends to have too fast flow and pick up stuff when you don't want it picked up. Things like small fish, plants, etc?
My favorite water wand is this el cheapo. I add enough tubing to press fit on the end to run to the drain.

It has a squeeze bulb to start the flow very easy as well as a good design to let me get down into the gravel if I want as well as the large section to sort out the sand. There is also a grid over the end to stop it if I run it across the top of some fry that I don't notice.

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Thank you both for the info! I'm slowly getting a methodology down for cleaning the sand. I also found a smaller siphon downstairs that has an angled end that will come in handy.

Interesting pictures! There were a few times when my fry wished for a grid like that!
I like the grid for saving fry as I have sent a few down the drain. Once I see them passing through the tube, I call them gone as I'm not about to take a trap off to recover something that might already be half killed by the experience! I did so much sucking "Malawi wine" before I got the squeeze bulb that I may never taste another wine of any sort!
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