# Connecting 2 Eheim Filters together..!!!



## ziggy_909 (22 Jul 2008)

Does anybody have any experience of connecting 2 eheim 2028 filters together..?

i have a plastic/perspex rim around the top of my tank to support the glass slides, so each corner only has space for 1 spaybar or outtake bar
i have just got another pro 2 2028 to up the flow to approx 2000 lpr... 

Prob. more like 1000lpr...(before the flow rate post's start to pour in...  )  

as i have 2 spay-bars and out take bars (config. will have to be 2 back corners, 2 front corners ....) not an ideal situations...

if i connect the out flow of 1 filter to the intake of the other filter.. i think it will only have the flow rate of 1 filter just double filtering... am i right here?


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## a1Matt (22 Jul 2008)

There is probably many ways to do this.... 
The method you describe is series, if the first filter blocks then the second filter will get a reduced flow as well.
I would connect them in parallel with the use two tees as follows:

The intake bar goes into a tee.  Then one end of the tee goes to filter one's input and the other to filter two's input.
Same on the output. Take both outputs and put them into a tee. Then connect the tee to the spray bar.

The water takes the easiest path available. So if one filter clogs the flow will automatically go more to the other one.  Which is good as it provides some redundancy.

Hope that makes sense.

I'd be interested to hear other opinions...


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## Ed Seeley (22 Jul 2008)

The problem with connecting filters in either series or parallel is that you will reduce the flow.  If you stick to tubing of the same size then having two pipes going into one could almost halve the flow rate for that section!  The only way to do it would be to go up in pipe size before you connected them.  As the 2028s use 16mm pipe then I would look at stepping up to 22mm at least and I'm not sure what you can get in the way of fittings here!  To reduce turbulence ideally use a Y-piece rather than a T so you don't have the flows hitting each other at 90 degrees.  In other words, if at all possible, make extra room to have them running in and out of the tank separately.


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## ceg4048 (22 Jul 2008)

Yes, theoretically you would need to at least double the tube diameter 16*2=32 mm for the joined section otherwise each input would back-pressure the other.

Cheers,


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## Ed Seeley (22 Jul 2008)

ceg4048 said:
			
		

> Yes, theoretically you would need to at least double the tube diameter 16*2=32 mm for the joined section otherwise each input would back-pressure the other.
> 
> Cheers,



You wouldn't need to double the pipe's diameter as their cross section is Pi times radius squared.

Therefore 16mm pipe has a cross-sectional area of 805mm2 (rounded up) and 22mm pipe has a cross-sectional area of 1521mm2 (again rounded up to the nearest mm).  So almost double the cross section therefore, theoretically, double the potential carrying capacity.  Although it can't hurt to go as large as possible with external filters as they function at almost zero static head but have a relatively large frictional head from the pipework.  The only static head they have to work against is to pump the water from the water's surface over the tank's rim.


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## ziggy_909 (22 Jul 2008)

i have the modular eheim taps on 1 pump and the green pipes on the other .... the green one's are so dam green

i really and trying to get some equipment out of the tank.... but unless i get a fx5 filter which aint gonna happen soon im a bit stuck

i can fit one modular and one green eheim pipe into each corner.. although one is grey and 1 is green... are they available in different colours? 

ceg4048 i notice you have 3 spay-bars connected in series on your tank (am i correct?) are these connected to 1 pump, and if so whats the spay power like using a longer tube, i.e is it uniform over the entire length of the pipe, i was thinking of having a 4 foot spay-bar in modular setup with with each end connected to a different filter... like a loop setup and having two up take pipes beside them... 1 each side


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## ziggy_909 (22 Jul 2008)

> Ed Seeley said:
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it there any point to this if i have to reduce the pipe size to normal 16/'22 to get it into the filter again....it will just slow the flow and back it up again..


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## ceg4048 (22 Jul 2008)

I actually have 4 spraybars distributed across the back, 2 bars joined and fed by each of two filters. This produces uniform flow across the the length of the bars. If we are talking about 4 corners then what might work is to ditch the Eheim suction tubes and use glass inlet tubes at the front to be less obtrusive with the spraybars at the back. Glass is expensive though. Maybe Fluval have something plastic and transparent...

Cheers,


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## Ed Seeley (23 Jul 2008)

ziggy_909 said:
			
		

> it there any point to this if i have to reduce the pipe size to normal 16/'22 to get it into the filter again....it will just slow the flow and back it up again..



After the T-piece it will be fine to go back to the 16mm pipe as that is large enough for the filter's flow.  You would only have problems trying to get two filters worth of flow into one 16mm pipe, if you see what I mean?


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## mick b (23 Jul 2008)

Ed Seeley said:
			
		

> ceg4048 said:
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Hi Chaps,

Not wishing to be 'clever' (as the newbie0 but the statement re-flow is correct, but the figures are off by a factor of 4

16mmDia has a cross-section of (16x16 x 3.142)/4 = 201mm sq
22mm Dia has cross-section 0f (22x22 x 3.142)/4 = 380mm sq

But the advice re plumbing is correct IMO/E

Cheers,  Mick B


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## mick b (23 Jul 2008)

sory don't know how to edit???????????????

should read (22 x 22 x 3.142)/4 = 380 mm sq 

Now found the Edit button!!! As I said NEWBIE!!!!


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## Ed Seeley (23 Jul 2008)

Sorry I used diameters rather than radii.

Should have been 8mm squared times pi and 11mm squared times pi.


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