# Running two filters through single hoses



## Danny (3 Mar 2018)

In the past I have daisy chained filters for added filtration, I'm considering running two of the same externals through the single in/out pipes by joining them with a Y piece. 

Has anyone else done this? Can anyone think of any potential problems? 

I'm more interested in increasing flow rather than filtration and it's cheaper with more combined flow to run two the same than upgrade to a bigger single of the equivalent combined flow rate.


----------



## Edvet (3 Mar 2018)

Never did this, but i would use   a double intake, i don't see a problem with a single outflow.


----------



## Angus (3 Mar 2018)

Edvet said:


> Never did this, but i would use   a double intake, i don't see a problem with a single outflow.



As long as the flow rate matches, if it doesn't, it could lead to pump head O-Ring failure long term.


----------



## Danny (3 Mar 2018)

When I chained multiple externals before I did it with Rena xp2's, out to in and so on and it worked fine.

It's just running two via single pipes I'm not certain on as I haven't before, it would be two Eheim 2213's.

What would make you go for two intakes @Edvet?


----------



## Angus (3 Mar 2018)

Danny said:


> When I chained multiple externals before I did it with Rena xp2's, out to in and so on and it worked fine.



Thats because if you run them in a chain they are all running on the same flow rate and same pipework, its just matching flow rates is all, because if you don't you will have a back pressure to the canister unit leading to the pump seal failing.


----------



## ian_m (3 Mar 2018)

No you cant join two filters to a common inlet or outlet. If there is any issue with one of the filters, eg turning it off to clean, slight blockage etc the other filter will push the water backwards through the filter, emptying all the cr*p into your tank, probably wiping out you fish. People on this forum have done this and have ended up emptying their filter contents into the tank.

You must keep the keep the filters pipe work separate.


----------



## MDP91 (8 Mar 2018)

As above, I looked into this long ago and opted not to. Seems the issues that can arise far out weigh the pro's. If you want better flow you'd be better picking up a couple of cheaper wavemakers.


----------



## Oldguy (17 Oct 2018)

ian_m said:


> two filters to a common inlet or outlet.


I can see a potential problem with a common outlet but not with a common inlet, assuming the flow through the common feed pipe is high enough so that the two pumps have sufficient water for their output flow rates. If one pump fails then the water in that canister remains in that canister. The second pump continues working, drawing water into its canister and out to the tank through its dedicated output pipe without any impact on the first canister with the failed pump.


----------



## ian_m (17 Oct 2018)

Oldguy said:


> If one pump fails then the water in that canister remains in that canister


No, the water doesn't stay in the non working filter. The working filter will draw the water backwards through the non working filter, thus pulling out all the carefully filtered detritus into the working filter.


----------



## Oldguy (17 Oct 2018)

ian_m said:


> No, the water doesn't stay in the non working filter


Surely the flow through the common feed greatly exceeds any back flow through the second canister especially as it will be filled with filter material.


----------



## ian_m (18 Oct 2018)

Oldguy said:


> Surely the flow through the common feed greatly exceeds any back flow through the second canister especially as it will be filled with filter material.


No. The pressure at the joint of the two filters and inlet pipe will be the same when the remaining working pump is pumping (obvious really !!), thus there will be the same pressure difference between the plain intake and intake of the non working filter. A pressure difference causes water to flow. The flow from the plain intake side will obviously be greater due to less resistance, but there will be a flow backwards through the filter.

This has been seen by people here who miss plumb their filters.

The worse case I have heard of here, is where someone connected two filter outputs into a common pipe (filters having individual intakes). One filter failed and the working filter pushed the water backwards through the non working filter, filling the tank with masses of detritus and killing fish and making a massive mess of the tank.


----------



## Oldguy (18 Oct 2018)

ian_m said:


> No. The pressure at the joint of the two filters and inlet pipe will be the same


Many thanks for your well reasoned response.  I have some new plumping to do but it will have to wait until I can get a quart into a pint pot. My mind is working on this, the best outcome will be a second service cupboard which would make life much easier. Thanks again.


----------



## ian_m (18 Oct 2018)

This is how you use two filters with CO2 injection on a tank.


----------



## Oldguy (18 Oct 2018)

ian_m said:


> This is how you use two filters with CO2 injection on a tank.


Thanks but I use an in tank pump with the inline diffusor also in the tank. There was a case on the CO2 forum of an inline diffusor splitting and the guy coming back from his holidays to find most of the tank water on his lounge floor. My canisters are for general filtration. My set up is moving from low to moderate tech. Depending on plant growth I might add a second in tank pump and diffusor.


----------



## Zeus. (18 Oct 2018)

It could be done by fitting non return valves post filter on both lines so the same inlet and returns could be used.

But with a hit on decreased filter output plus I think the detritus build up around them would decrease their non return function over time. So I would agree with Ian's reply with reference to the KISS principle


----------



## Barbara Turner (30 Oct 2018)

If you haven't bought a second filter yet, another option might be to remove the internals of the pump from your  from your current filter and buy a jecod / jebao pump. I went for the DCS-4000 that gives me a pump capable of 4000 litres an hour.


----------

