# Two filters / one inlet and outlet?



## James D (28 Feb 2014)

Just an idea, has anyone tried using a splitter to run two filters through one set of lily pipes? I want to increase my flow but I don't want the extra glassware etc in my tank. In theory I could use 16/22 pipes and glassware split into two 12/16mm pipes going into two eheims.

Something like this

I can't see why it wouldn't work but there's probably something I haven't thought of.

Thanks

James


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## Martin in Holland (28 Feb 2014)

Hmmm....interesting I would like to know if this works too


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## ian_m (28 Feb 2014)

No you can't combine inlets and outlets of two of more filters easily as you think.

If one of your filters is not as powerful as the other (or you turn one off to service it) may end up forcing water through one of the filters backwards, thus emptying the filter gunk into your tank.

Two filters, means two inlets and two outlets, unfortunately.


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## geoffbark (28 Feb 2014)

As Ian says! It is not easy to do. But is doable with non return valves and protection systems to stop reverse flow and the pumps fighting each other. I would not bother and just run two independent filters


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## tmiravent (28 Feb 2014)

Hello,
I use a similar solution in my filtering configuration. 
One outlet and one inlet for everything.
I use the outlet tube to feed the filter and for water change (in and out) at the same time (no problems).
It works. My split is a T, not so good as your suggestion (difficult to find here!)
I use security valves in each part, for easy maintenance and cleaning.
Till today this is my favorite filtering configuration (but is very personal).
Very comfortable to use, clean and maintain.
The not so good side is:
- you lose filtering power in longer pipes/and twists
- much more complex to mount, you should make double check in every connections
- more expensive
I would guess that 16/22 is better but 12/16 will also work.

Here is my filtering system:



 





James D said:


> Just an idea, has anyone tried using a splitter to run two filters through one set of lily pipes? I want to increase my flow but I don't want the extra glassware etc in my tank. In theory I could use 16/22 pipes and glassware split into two 12/16mm pipes going into two eheims.
> 
> Something like this
> 
> ...


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## Dan Wiggett (28 Feb 2014)

About the only way it could be done!


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## NC10 (1 Mar 2014)

How about only one outlet but two returns? Would this still cause problems?


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## tmiravent (1 Mar 2014)

In theory i think it can be done that way (one outlet and two returns) and also with 1 return and 2 outlet's.
If the forces have  the same direction and no stress (to small tube in one part)  it should work.
James D. objective is to use only one inlet and one outlet but to use two filters.

It can be done in line or parallel.
In line the stronger filter should be the last and the other should be power off (it's passive).
In parallel the two filters should be power on and the flow must be much stronger (better to use larger pipes when they join the flow.
The real advantages should be tested, analyzed and calibrated to each particular tank.
It's fun to change the way things 'should work' but 'standard' way is pug and play (tested and easy).
Also remember that sometimes upgrading for one powerful filter could be a better solution (that a look at the tank, power consumption/flow rate,etc)


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## NC10 (1 Mar 2014)

One return won't work though, because of some of the points already made.

I'm pretty sure back pressure is what everyone is getting at, the pumps fighting each other, the strongest will obviously always come out on top, ultimately leading to damage of one or both pumps. I'm not sure if they're even the same type pump/filter he wants to connect, but one will no doubt be slightly stronger even if they're the same.

Going along with James D original plan and knowing one return isn't possible, only having one outlet obviously reduces any visible pipe work by one, if it works that is. It's one less anyway 

If you have one pipe with a bigger diameter coming from the tank and then split to the filters, I can't see why this wouldn't work. Maybe even same diameter would work. There's a lot of siphon/gravity involved which should be able to supply both pumps with the required water. They wouldn't be fighting each other as long as the required water for each pump is being fed. The fighting comes after the pump.

You could have 2 pumps needing a 60/40 split of what ever water is required, or 3 pumps requiring a 10/40/50 split of what is required etc etc As long as 100% is being supplied (adequate pipework) and they're all running an outlet each, I can't see an issue.

That's my thinking anyway


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## ian_m (1 Mar 2014)

No it can't be easily done two filters and only one set of pipes. The two issues are pumps fighting each other and what happens of one pump fails.

On another forum there is a brilliant example of feeding two pumps into one outlet and owner accidentally forgot to turn one pump on after maintenance. Ended up reversing the flow on one pump, the off one, and emptying the filter contents into the tank, killing his fish. He had mixing valves etc to equalize flow but failed to take into account what happens on failure.


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## James D (3 Mar 2014)

Well, this has turned into a more interesting discussion than I anticipated. Thanks for your excellent diagram tmiravent, it's far more complicated than I thought it would be though. Although I enjoy trying new DIY projects I think I'll leave this one alone!

Thanks for all the informative answers everyone.


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