Backyard Aquaponics
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Wondering about placement of the inlet for a radial flow filter. Most designs have this inlet in the center of the container, but is there any reason why it can't be on one side?

Hi
Yes,but! No but!
I wrote a post on RFF design some time ago. Try IBC part 2
I was hoping to get Stuart to comment. I understand he is a busy, ‘bee’ but he has forgotten more about water flow dynamics whilst I am still turning the tap on.
Perhaps this time.
As I understand it;
Water flow is up_down -up
A piece of detritus flows up the tube, It then reverses direction downward.
In addition to the downward flow of the water force is added by gravity.
If these two forces combined exceed the, upward force, of the water in the outer part the detritus will continue on down.
An accepted ratio is that the’ inner damping cylinder’ is 25% of the outer.
This gives the, radial flow to the outside.
The immediate observation is that an off centre inlet pipe will have different flow rates on the, close side to the wide side.
But what do I know?
I can’t tell a tap from a faucet!

yes, it will have different flow on one side than the other, but will it affect the filtration rate?

I've now seen a few examples of RFF like this, with the inlet to one side, so I think I'm gonna be fine.

It can make a difference but it might not make much of a difference



In this design the flow is coming in the orange pipe and out the green one. The flow is directed down the outside of the orange pipe by the large pipe that forms a sleeve about the orange pipe. For the solids to get out they then have to go back up and then get sucked in to the green pipe. This isn't likely but it is possible. If the orange pipe and the green pipe where as far apart as possible it might work a bit better but it might you might not notice.

Where it could make a significant difference is where the flow through the filter is getting close to maximum for the size of the filter.

In any case since making it better only involves a few extra inches of orange pipe to get it to the far side of the barrel I'd recommend everyone do it just to be sure.

Thanks Stuart. I'm in the filter design stage now. Which type is this one? RFF?

Yep.

Easier to make than a swirl filter and they work much better.

Well, in my case, I'm coming up from a bung, so the orange pipe would be over to one side without adding more pipe.

Vela, what type of drum are you planning to use? I'm just trying to grasp the design. 2" and 3/4" bungs or the double 2"? (Although all the double 2" I've seen have different threads on each side.) Maybe you could cut a hole for the inlet, use the 2" bung for outlet, and use the 3/4" for a ball valve solids drain ...

It's a 55 gal (200 l) with double 2" bungs. It has different threads, one is NPT, the other is the bung thread. I'd like to use the Bung as the inlet, the other bung with the 3/4" as the drain, and the outlet on the side.

I really don't see how moving the inlet over would make a big difference in the function of the filter, and it saves me from making another hole. I'm lazy like that.

Not sure what you guys are talking about re the inlets and outlets.

A RFF has three pipes connected to it. One to take the flow from the FT (orange pipe), one to go onto the next component (green pipe) and one to remove the solids (not shown).

orange is inlet to the RFF.
green is outlet.
drain is solids removal.

My situation is that I have a barrel with 2 bungs, they are at opposite sides of the barrel. I was thinking of using one bung as an inlet, but have the typical outlet, like the green pipe above. Now, the difference is that the inlet (orange), instead of being in the center of the barrel would be to the opposite side of the barrel from the outlet. Would this significantly affect operation?

I've heard arguments both for and against, though no one is exactly sure, and I think everyone agrees difference would be insignificant, at best.

Is it? I had a swirl filter on my fish pond, but switched to RFF after reading here they performed better. I didn't like the way the swirl fliter screen would get clogged with solids that were difficult to remove. Having said that, I sometimes wonder if putting some screening material in the RFF would be helpful.

Wouldn't be surprised if having it placed centrally might matter more for a cone bottom tank. Have you made your filter Vela and how is it working if you did?

If you have sized the RFF relative to the flow correctly it shouldn't make any difference at all.

All the large particles that a screen would catch should sink to the bottom. A finer screen would restrict the flow too much and over flow the filter.

Whether its a flat bottomed filter container or a cone should make any difference. Its all about maximising the distance that water has to flow to get out of the filter.

In a commercial RFF with a weir around the outside of the filter container then in the inlet should be in the center. If the out let is on one side of the filter container then the inlet should be on the opposite side.