Waterflow Slowly Coming to a Halt - The Planted Tank Forum
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post #1 of 18 (permalink) Old 06-22-2020, 05:43 PM Thread Starter
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Waterflow Slowly Coming to a Halt

Hello,

I have been experiencing a loss in the water flow in my tank. I have an Eheim 2217 filter, which is attached to a reactor canister. I know that this reactor reduces the flow of water a little bit, but when I initially installed it, the flow was still good, however I've seen it slow down over the weeks, and it is currently so weak that it is not enough for a healthy tank. I have cleaned the intake to make sure it is not clogged with plant leaves and other debris, but the flow remains weak so I am not sure what else to do. Is there a recommended inflow / outflow diameter for a 50 Gallon tank (ADA 90P to be exact)?


Thank you in advance.


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post #2 of 18 (permalink) Old 06-22-2020, 05:46 PM
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Probably a silly question, but have you cleaned the filter media?

“Science, my lad, is made up of mistakes, but they are mistakes which it is useful to make, because they lead little by little to the truth.” -Jules Verne
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post #3 of 18 (permalink) Old 06-22-2020, 06:10 PM Thread Starter
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I set up the filter in this aquarium only a few weeks ago. I have another tank whose filter has not been cleaned in well over 5 months, and the flow of water is pretty powerful, this one has been running, like I said, for only a few weeks, and it is already at the point where water is barely flowing at all. I will clean it anyways, just to try that, but I doubt that it will do anything


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post #4 of 18 (permalink) Old 06-22-2020, 06:15 PM
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When I ran a canister, the flow was my way of knowing when to clean it. YMMV, but there is something impeding flow, and you have cleaned the prefilter. If cleaning your mechanical media doesn't help, its time to look in the reactor.

“Science, my lad, is made up of mistakes, but they are mistakes which it is useful to make, because they lead little by little to the truth.” -Jules Verne
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post #5 of 18 (permalink) Old 06-22-2020, 06:26 PM
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Is it possible that the filter is too far below the tank? From what I've read, the maximum head height appears to be 4-6 feet (depending on whether the filter contains media or not).

If it isn't too far below, I would try cleaning everything that could impede flow (prefilters, reactor, filter foams and biomedia, even the impeller/motor if it is accessible).
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post #6 of 18 (permalink) Old 06-22-2020, 06:41 PM
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Quote:
Originally Posted by sm1ke View Post
Is it possible that the filter is too far below the tank? From what I've read, the maximum head height appears to be 4-6 feet (depending on whether the filter contains media or not).

If it isn't too far below, I would try cleaning everything that could impede flow (prefilters, reactor, filter foams and biomedia, even the impeller/motor if it is accessible).
You don't really have any head height on a canister filter, though the extra friction of the tubing can slow things down. if you think having a canister too far below a tank slows it down, does that mean that putting it above the tank would speed it up?

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post #7 of 18 (permalink) Old 06-22-2020, 07:05 PM
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Originally Posted by Bunsen Honeydew View Post
You don't really have any head height on a canister filter, though the extra friction of the tubing can slow things down. if you think having a canister too far below a tank slows it down, does that mean that putting it above the tank would speed it up?
Head height is mentioned quite frequently on product pages. Maybe they list the head height because as you said, longer lengths of hosing result in extra friction which can slow flow down. Either way, if the filter is too far below the tank, the hoses must be longer than what the manufacturer recommends, which again as you said, could result in reduced flow.

Put it this way. Knowing the head height could be important because he could be using a hose that is too long.

EDIT: @Chizpa305: I checked your journal thread. Looks like the issues may have started after switching to silicone hoses and new inflow/outflows. The old inflow did not have a skimmer, and the old outflow was a spraybar. The first thing I would do is definitely try to clean the plumbing as best you can to ensure there are no clogs. After that, if possible, I'd try swapping the Eheim hoses onto the new inflow/outflow to see if there is a difference in flow. If there is no difference, I'd try the silicone hoses with the Eheim inflow/outflow. You should be able to at least narrow down what's causing the flow problems by process of elimination, in theory.

Last edited by sm1ke; 06-22-2020 at 07:24 PM. Reason: added info
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post #8 of 18 (permalink) Old 06-22-2020, 08:16 PM
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Quote:
Originally Posted by Chizpa305 View Post
I have been experiencing a loss in the water flow in my tank. I have an Eheim 2217 filter, which is attached to a reactor canister.
So, what have you done to narrow down the problem? Have you already established that the reactor is the reason for loss of flow? Have you already established that the reactor is NOT the reason? Hoses? Prefilters? Something else?

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Originally Posted by sm1ke View Post
Is it possible that the filter is too far below the tank? From what I've read, the maximum head height appears to be 4-6 feet (depending on whether the filter contains media or not).
Canister filters are not limited by head height. It doesn't matter how far the canister sits below the tank, as long as the canister seals can hold the water pressure. The flow does not depend on height difference at all (aside from extra friction in longer hoses).
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post #9 of 18 (permalink) Old 06-22-2020, 08:45 PM
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Originally Posted by AndreyT View Post
Canister filters are not limited by head height. It doesn't matter how far the canister sits below the tank, as long as the canister seals can hold the water pressure. The flow does not depend on height difference at all (aside from extra friction in longer hoses).
Head height is mentioned quite frequently on product pages. Maybe they list the head height because as you said, longer lengths of hosing result in extra friction which can slow flow down. Either way, if the filter is too far below the tank, the hoses must be longer than what the manufacturer recommends, which again as you said, could result in reduced flow.

Put it this way. Knowing the head height could be important because he could be using a hose that is too long.
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post #10 of 18 (permalink) Old 06-23-2020, 04:44 AM
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Perhaps they mention it for marketing reasons, since it is important in sump return pumps. It doesn't matter for a canister because it has water in full siphon coming in which balances the energy required to push it back out, minus friction / blockage.
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post #11 of 18 (permalink) Old 06-23-2020, 07:49 AM
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Head height is a standard characteristic of a pump, any pump. So, they publish it as part of a standard boilerplate.

However, static head in a closed system, like a canister filter+plumbing+tank, is always zero (or near zero). Which means that canister filter pump does not work against gravity, it does not work against height. It only works against drag in the hoses and drag in the filtering media.

I often notice that canister filter manufacturers themselves make this mistake. In their user manuals they sometimes refer to their canister filters as "gravity fed" systems and claim that placing the filter lower than the pump's head height will prevent it from working. This simply means that they apparently employ some physically-illiterate low-cost writers for these manuals. Canister filters are gravity neutral systems (not "gravity fed"), and their pumps are completely insensitive to height.

Again, I don't advocate ignoring the declared height limitations. Exceeding declared height difference bears a completely different risk: increase of the internal pressure and, consequently, blown seals and leaking canister. But this has nothing to do with the pump.
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post #12 of 18 (permalink) Old 06-23-2020, 01:46 PM Thread Starter
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Quote:
Originally Posted by sm1ke View Post
Head height is mentioned quite frequently on product pages. Maybe they list the head height because as you said, longer lengths of hosing result in extra friction which can slow flow down. Either way, if the filter is too far below the tank, the hoses must be longer than what the manufacturer recommends, which again as you said, could result in reduced flow.

Put it this way. Knowing the head height could be important because he could be using a hose that is too long.

EDIT: @Chizpa305: I checked your journal thread. Looks like the issues may have started after switching to silicone hoses and new inflow/outflows. The old inflow did not have a skimmer, and the old outflow was a spraybar. The first thing I would do is definitely try to clean the plumbing as best you can to ensure there are no clogs. After that, if possible, I'd try swapping the Eheim hoses onto the new inflow/outflow to see if there is a difference in flow. If there is no difference, I'd try the silicone hoses with the Eheim inflow/outflow. You should be able to at least narrow down what's causing the flow problems by process of elimination, in theory.
You are right, the problem sort of started from there, although it was not noticeable at the beginning. One thing I did notice and it was that the filter inflow / skimmer has a fairly narrow neck that connects to the hose. So it could be that I need to get one with a wider diameter... I will go ahead and change the current silicone hoses with the Eheim ones temporarily and wait a few weeks to see if the problem persists, then at least I will know that the hoses are not the problem.

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Originally Posted by sm1ke View Post
Is it possible that the filter is too far below the tank? From what I've read, the maximum head height appears to be 4-6 feet (depending on whether the filter contains media or not).

If it isn't too far below, I would try cleaning everything that could impede flow (prefilters, reactor, filter foams and biomedia, even the impeller/motor if it is accessible).
No, this would not be the issue. My canister sits inside the cabinet, right under the tank. It is a standard sized cabinet like the ones used by ADA. It is not an ADA, but custom made using similar dimensions, so that would not be the problem The hoses are not too long, except that the water does have to go through the reactor and that could add some resistance to the flow, but other than that, everything is pretty much standard. I know that reactors usually reduce the flow, but it should not make it go to a halt. Right now my filter inflow / skimmer is only sucking water through the skimmer portion since I closed the other section of the intake. I did this because the skimmer was just not doing anything, and to force the surface to be better cleaned by increasing the skimmer suction, however at this point even the skimmer intake is so weak that it barely does anything. This is causing bigger problems like too much CO2 getting dissolved in the water due to poor flow. I disconnected the CO2 until I get his sorted out.
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post #13 of 18 (permalink) Old 06-23-2020, 02:47 PM
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Canister Head Pressure information:

Click below and for a good explanation Head Pressure and read the entire article here "Real World" Canister Filter Flow Rates:

https://www.aquarium-pond-answers.co...-and-pond.html

Here is an actual test using the Filstar S (manufactures rated at 250 gph) and timing its flow to fill a container. Note: -34% just plugging the unit in level with the aquarium and NO media!

Level with the aquarium - 164.53 gph
24" below the aquarium - 153.00 gph (-7%)
52" below the aquarium - 142.87 gph (-13%)

These results were with a filter with NO resistance in the filter (all media was removed). The tubing was not cut, shortened or lengthened (as tubing length can also change results by adding more water resistance).

What is noteworthy is that despite this siphon aid, tests and 1000s of practical use applications show that there is still a drop in flow rate for a closed system canister filter due to friction, tubing size, devices such as UV Sterilizers, CO2 equipment, etc. along with some impact from head pressure.

Another example is the Fluval FX6 with a 0 head pressure rating 925 gph, when in reality the typical head pressure flow rate is 600 gph or less after the added resistance in the filter media and tubing are applied (as well as the addition of a UV Sterilizer).

Though it's far from an exact formula, a typical pump/canister filter flow rate with an under tank placement is about 50% to 60% of the published 0 head flow rate. This is the number you should use for mating your UV Sterilizer.
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post #14 of 18 (permalink) Old 06-23-2020, 05:22 PM
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What is noteworthy is that despite this siphon aid, tests and 1000s of practical use applications show that there is still a drop in flow rate for a closed system canister filter due to friction, tubing size, devices such as UV Sterilizers, CO2 equipment, etc. along with some impact from head pressure.
I highly doubt that there was an impact from head height itself (aka "static head").

As the tester stated, they used tubing of the same length for all canister placements. I's assume that even though the length was the same, the "kinks" in the tubing were different, which is what contributed to the difference in the flow. Again, in a canister filter system, the pump does not lift water. The author of the article at the link explains it fairly well: sump pump lifts water, canister pump does not lift water.

Also note that they state: "Impeller, intake, internal flow, and exhaust design will also play a role, as I have seen one canister filter brand barely affected by placement, whereas another is much more affected by filter placement." Again, this is another indication that the difference is not caused by static height, but rather by something else.
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post #15 of 18 (permalink) Old 06-23-2020, 06:05 PM
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So we have the classic situation here.
We have Eheim who is pretty well known as a long term success in the field of filters and they set limits on what height works best for their filters. On the other hand we have a low level, somewhat experienced hobbyist who says it doesn't matter!
So we get to choose whose advice to follow???
When I see the hobby fellow come up with a filter proving he knows more than Eheim, I will change my mind but for now, I'm blowing him off!

I suggest checking the manual for proper operation!
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