Plumbing for two Eheim II Pro filters. - The Planted Tank Forum
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post #1 of 8 (permalink) Old 12-09-2003, 01:33 PM Thread Starter
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I recently added a second Eheim II Pro filter to my 90 gallon tank. I was previously unhappy with the amount of water movement and the ability to filter out small particles. So, now I am running an Eheim 2026 and 2028 on this tank.

To minimize clutter in my tank I really would like to run both of these filters on the same filter intake and output. So I went ahead and bought two T-junctions and some extra hose and set these filters up to run in parallel with one intake and output. Something like this:

intake --------<----------------------->-------- output

In addition I would like to run an inline heater and an inline CO2 reactor on this system as well. My initial idea for the setup was like this:

intake --------<--------------------------------->-------- output

Unfortunately, this setup does not seem to be ideal. The Eheim II Pro series has an output flow gauge. And on both filters the output seems to run only at 60-70%. When I turn off either one of the filters, the other will run at 100% immediately.

Could anybody with some plumbing experience let me know how to best set this system up? I would like the filters run at (or close to) 100%, I need to add both the heater and the reactor to the system and I would like to do the whole thing on one intake and output.

Do I just need to use a wider diameter hose and intake/output where both filters are joined? Do I need a wider diameter intake/output? Might an assembly like this one help? Any suggestions are welcome. Thanks for you help... mario

Btw. Please let me know if the schematics don't make any sense to you... I will try and post a better drawing or a digital picture of my actual setup.
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post #2 of 8 (permalink) Old 12-09-2003, 02:23 PM
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Great job on the schematics. Crystal clear to me.

That is a tricky one Mario. I don't think you will be able to plumb the two together. You would be able to run a CO2 reactor and inline heater, no problem. My suggestion to you is to go right to the "horse's mouth" and contact Eheim directly. Drop by their web page and follow the contacts link.


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post #3 of 8 (permalink) Old 12-09-2003, 02:54 PM
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My buest guess is that they are being restricted on the intake, you are trying to pull twice as much water through the same size tubing and are running into problems supplying the filters with enough water to push through at their regular flow rates. I would try larger tubing on the intake side first and see if that helps. i.e. at the T junction the tubing coming from your tank should be larger than the tubing going to either filter. Hope this helps.
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post #4 of 8 (permalink) Old 12-09-2003, 06:01 PM
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I think a lot of this is going to come down to the size of your pipe fittings, and the T's themselves. Every time you T a pipe you restrict the water flow significantly.

If I were you, I would try to get at least a 3/4" to 1" inlet before your T, then T it off to your smaller Eheim tubing (I think thats 1/2"). You will need to do the reverse on the outlet side.
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post #5 of 8 (permalink) Old 12-09-2003, 06:07 PM
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Ok.. just to give you some real numbers... Without running water at presure through a 1/2" pipe (I'm pretty sure thats the eheim tube )sizing you're only going to get approximately 300gph through a tube.

That means you are only drawing 300gph from your tank to the T, then cutting it in half.

If you were to increase your inlet to 3/4" you increase your rate of flow to around 720 gph to the T.

If you were to increase your inlet to 1" you increase your rate of flow to around 1200 gph to the T.

Clear as mud?
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post #6 of 8 (permalink) Old 12-09-2003, 08:07 PM Thread Starter
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Thanks for your replies, guys. It seems like I should be fine if I use Y-junctions that have two smaller outlets for the regular Eheim II Pro tubing and one larger outlet (3/4'' inner diameter?) and if I change the tubing on the intake and outlet to 3/4'' inner diameter tubing.

Has anybody of you used the Pentair Aquatics Customflo Water System? It says that it fits 3/4'' tubing; however I'm unsure if that is for inner diameter or outer diameter. Any ideas? Thanks... mario
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post #7 of 8 (permalink) Old 12-17-2003, 10:10 PM
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ok - imho - the single intake is ok but it's the return pipes thats the problem. both filters are pushing water out the return pipe.. one filter is stronger than the other and I suspect that your getting some backflow / back pressuge at the tee... sort of like running 2 bathroom fans on the one exhaust... not all the air is going to go out the intended pipe, some is going to go back the other pipe.

now on the single intake I think your ok but not positive - there is a bit of math involved to confirm that or not and I am no engineer... but to be honest your very best bet is run them seperatly - hide any excess clutter with more plants:-)

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post #8 of 8 (permalink) Old 12-18-2003, 07:09 AM
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Neither the intake nor the outlet should be restricted, seems pretty clear, if there is a finite amount of water that can pass through the pipes at the fixed amount of presure (pullin one side, pushing the other) these 2 pumps can generate together, well, it is the limit.

Solution, tubing which allows at least twice the flowrate of the thinner tubes after the T, with the thicker pipes on inlet and outlet...

38gph --------<------------------------------>-------- 38gph output

I just used imaginary numbers to illustrate.

Take into account the loss around elbows and Ts, and it should be clear that if you just use piping equal to the rated max throughput, and connect it to a T, you would get less than optimal flow, to overcome this you would need a larger bore on t's and inlet piping to the degree to which water is restricted otherwise. I.e. Big fat inlet and T connected to your regular eheim tubes would work perfectly... small inlet would kinda affect the pumps like someone sucking on the input a bit while its trying to draw water.

Same thing applies on the outlet side... If the Flow is restricted too much by the T and outlet pipe, the pumps would experience it as trying to blow against the stream, and get less than optimal flow.

more mud to make it clearer.
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