Oversize filters with flow control taps?

[Ben Lim]

I have a classic Eheim 2217 canister filter lying in my store for a few years now and was thinking of using it for my 2ft planted tank. I believe this filter is quite over size for the setup and I'm wondering by adding those control valves at water inlet & outlet can help to control the water to the appropriate flow rate. Or any other suggestions from member here?

[cairocks]

From what I understand, only restrict the output flow rate of the filter but not the input side. This is to ensure at least chambers are always filled and it is not overworking trying to pull water into its chambers. I also used an oversize filter for my 2 ft planted tank. But I do not use any valve, instead, I run the output water through a fluidized bed filter, a chiller and a external CO2 reactor before letting the water return to the tank via a rain bar. Had this setup for 1.5 years already and everything seems fine.The fishes are relax and not swimming in a whirlpool. Hope this helps.

[peter2883]

I think you should never overwork your canister no matter what... By doing so in your case by restricting either inlet or the outlet makes your canister work harder...

Maybe you can add a rainbar but face the it on the wall of the tank at least this slows down the speed...

But take it this way the more you cycle your tank the cleaner it will be...

I'm running around more than 10 times the volume of my 200 litre tank...

[cairocks]

I think you should never overwork your canister no matter what... By doing so in your case by restricting either inlet or the outlet makes your canister work harder...

Yea, but being having to run water through a chiller, I have to use a filter anyway. Don't think it is a good idea to run unfiltered water into a chiller. By the way, the filter I used is a 960l/hr one for my 90 liters tank. On the other hand, had been contemplating if I should add a delicated filter to drive the chiller recently.

[Eralf]

I think you should never overwork your canister no matter what... By doing so in your case by restricting either inlet or the outlet makes your canister work harder...

Maybe you can add a rainbar but face the it on the wall of the tank at least this slows down the speed...

But take it this way the more you cycle your tank the cleaner it will be...

I'm running around more than 10 times the volume of my 200 litre tank...

Er... I'm wondering. How does anyone work a centrifugal pump too much?
I'm not mechanically trained, but I can't see how restricting water flow would over work a centrifugal pump.

A centrifugal pump in our aquarium pumps and filters are dumb systems, it does not adjust itself to its load or anything like that. The magnetic 'drivers' would just spin the impeller, the impeller would cause a pressure increase of the water near the end of the impeller blades due to Bernoulli's principle,the pressure is relieved by having the water flow out from the pump's outlet (preferably), or just back out the 'intake' of the impeller housing.

The impeller would just spin at more or less the same speed regardless of the fluid pressure, so any wear would still be the about the same. It's not smart that it would try to spin faster to achieve a consistant flow rate when there's a restriction. The only difference I can think of would be the cooling effect of flowing water on the heat produced by the impeller drivers. But it should not be significant as long as water is still flowing and more so if the water temperature is already below ambient temperature.

Logical? Just try. Block the intake of your pump or filter or squeeze the tubing shut. The impeller would still be happily spinning, although failing to pump any fluid.

[cairocks]

The thing that worries me of the pump being over worked is that sometimes when there is a suction failure, like having air suck into the filter when changing water. When trying to get the suction going again, there is some sort of sound coming out of the filter. Sort of griding, knocking etc sounds. Once the suction is established, and the water flow is re-established, these sounds tend to stop. The presence of such sounds gives the impression that some sort of stress is happening inside the filter pump.

[Ben Lim]

Thanks you all for the valuable advice. Will give it try.

[Eralf]

The thing that worries me of the pump being over worked is that sometimes when there is a suction failure, like having air suck into the filter when changing water. When trying to get the suction going again, there is some sort of sound coming out of the filter. Sort of griding, knocking etc sounds. Once the suction is established, and the water flow is re-established, these sounds tend to stop. The presence of such sounds gives the impression that some sort of stress is happening inside the filter pump.

Ah! I see. That's the sound of water turbulence. When the impeller's chamber is not totally filled with water, the impeller is slapping the water around the chamber and the water is slapping the surface of the chamber. This causes the sound, just like you'll hear a sound when you slap the surface of the water.

When the chamber finally becomes filled, the sound stops, just like you waving your hand under water would not cause any sound.

I have a valve at the intake of my Eden 501. The water flow at the intake is reduced, resulting in a slower output as well (You won't need 2 valves, 1 will do the trick). Unless there's a leak somewhere in the canister or plumbing, air will still not get into the canister, so you need not worry about
the canister not filling. I can totally shut off the valve, the pump would just stop pumping water, it would not empty the canister. Don't worry, the pump doesn't produce enough pressure to empty the canister leaving a vacuum.

[ankank]

The water flow at the intake is reduced, resulting in a slower output as well (You won't need 2 valves, 1 will do the trick).

Just a quick note: Just about every manufacturer of external filters, including eheim, recommend throttling the outlet side only.

Which I don't think has got much to do with the pump, but rather with the whole canister and its gaskets etc. being designed for a certain pressure range. With throttling the outlet side, the only pressure change is overpressure directly after the pump. Whereas when throttling the inlet side, the whole canister becomes underpressured, possibly drawing air from the gaskets and underpressure outgassing which will eventually concentrate in the pump chamber.

[Eralf]

Just a quick note: Just about every manufacturer of external filters, including eheim, recommend throttling the outlet side only.

Which I don't think has got much to do with the pump, but rather with the whole canister and its gaskets etc. being designed for a certain pressure range. With throttling the outlet side, the only pressure change is overpressure directly after the pump. Whereas when throttling the inlet side, the whole canister becomes underpressured, possibly drawing air from the gaskets and underpressure outgassing which will eventually concentrate in the pump chamber.

Hmmm... I see... Yes, that makes sense. Thanks for sharing!

[tcy81]

so if the canister filter is connect a chiller, you will only need to connect a flow control valve on the output side of the chiller ?

[BFG]

Filter, not chiller. But if connected to chiller, for sure the flow will be lessen.

[tcy81]

Filter, not chiller. But if connected to chiller, for sure the flow will be lessen.

ok. if still flow still strong , connected at the out put filter side before chiller ?

[Eralf]

Just a quick note: Just about every manufacturer of external filters, including eheim, recommend throttling the outlet side only.

Which I don't think has got much to do with the pump, but rather with the whole canister and its gaskets etc. being designed for a certain pressure range. With throttling the outlet side, the only pressure change is overpressure directly after the pump. Whereas when throttling the inlet side, the whole canister becomes underpressured, possibly drawing air from the gaskets and underpressure outgassing which will eventually concentrate in the pump chamber.

I just thought of something. If the filter is placed below the tank, and the valve at the outlet side, and with gravity feeding the water down into the canister, wouldn't the whole canister be under overpressure?

So if we place a valve at the inlet side, reducing water flowing from the tank into the canister, we could reduce this overpressure or create an underpressure at the canister. Personally, outer than the problem with outgasing of dissolved gases, I prefer to have the canister under underpressure, so if there's any tiny leaks, air would get into the can instead of water coming out of the can and flooding my room...

[ankank]

If the filter is placed below the tank (...) with gravity feeding the water down into the canister, wouldn't the whole canister be under overpressure?

Theoretically, yes. In practice, a filter that is placed 1 meter under the tank's water surface receives a pressure of roughly 0.1 bar (9,807 kPa) from the piping. That is hardly noteworthy at all.

so if there's any tiny leaks, air would get into the can instead of water coming out of the can and flooding my room...

If the gaskets are leaking so much as to flood your room, you'll have a problem either way. Again, in practice, a gasket should not be leaking, period. And you probably wouldn't notice a slightly leaking gasket at all, a few ml a day will just dry up on the outside of the filter case. Whereas you will absolutely notice a few cm³ of air drawn into the filter.

[Eralf]

Theoretically, yes. In practice, a filter that is placed 1 meter under the tank's water surface receives a pressure of roughly 0.1 bar (9,807 kPa) from the piping. That is hardly noteworthy at all.


If the gaskets are leaking so much as to flood your room, you'll have a problem either way. Again, in practice, a gasket should not be leaking, period. And you probably wouldn't notice a slightly leaking gasket at all, a few ml a day will just dry up on the outside of the filter case. Whereas you will absolutely notice a few cm³ of air drawn into the filter.

Ah! I see I see. Thanks! So I guess it's time I change the position of my valves....