Another fx5 flow rate question

[knobhill]

hi,
I'm setting up a new (to me) 140g tank. It is already plumbed with pvc pipe into slip bulkheads so there would be a pretty big cost to swap out what is already there for new, larger diameter plumbing. I want to hook up my fx5 directly to what already exists. It will probably require a couple of hose barb fittings and reducers but that is minimal compared to redoing everything.

It has an overflow with three 1/2" returns, all tied in from a single line. The bulkheads, tees and pvc pipe are all 1/2" except at the very beginning and that is 3/4". There is a drainage bulkhead and that is 3/4" as well.

I have always used 1" vinyl tubing and/or pvc for my fx5s. That's just how I've always done it....

If I hook up my fx5 to the existing plumbing, will the smaller diameter piping restrict the flow very much?

 

[Fish Eat Fish]

Are you going to use the overflow with the canister? You run a risk of it not being able to keep up with the canister draw and overflowing the tank or running the canister intake dry. Maybe people do this successfully but an overflow is almost exclusively used to feed via gravity and not suction which a canister will do to come degree.

I could be missing something done commonly but I associate overflows with sumps which are not sealed systems.

 

[knobhill]

Yep, I forgot to add that I will put a 1" bulkhead with a strainer about 8" from the bottom on the overflow. This will make the water level in the overflow the same as in the tank.

 

[Fish Eat Fish]

I don't think that will work or atleast it will be very likely to fail if you don't always have the water level in your tank perfect. The input side of the canister always needs to be below the water level. You don't want it near the top or it will pull in air and lose siphon.

Honestly it sounds like you are trying to hybridize a canister and a sump which do not work the same way. When the amount of water changes in the system the water level in the sump will change because the tank is overflowing into it. A canister is 100% always full so the overflow system can't compensate for changes in water volume in the same way. I would think your only hope would be to put that bulkhead on the bottom of the overflow. Even in this case you will have a very finicky tank that always needs to have the right amount of water + or - a few gallons if it works at all. In the end it will always be more touchy then if you just ran a sump or just installed the canister correctly.

You could drill holes in the overflow if it is an internal design so that it doesn't function as an overflow anymore. This would allow it to work just like regular bulkheads into the side of the tank...but be needlessly more complicated.

 

[predatorkeeper87]

I don't think that will work or atleast it will be very likely to fail if you don't always have the water level in your tank perfect. The input side of the canister always needs to be below the water level. You don't want it near the top or it will pull in air and lose siphon.

Honestly it sounds like you are trying to hybridize a canister and a sump which do not work the same way. When the amount of water changes in the system the water level in the sump will change because the tank is overflowing into it. A canister is 100% always full so the overflow system can't compensate for changes in water volume in the same way. I would think your only hope would be to put that bulkhead on the bottom of the overflow. Even in this case you will have a very finicky tank that always needs to have the right amount of water + or - a few gallons if it works at all. In the end it will always be more touchy then if you just ran a sump or just installed the canister correctly.

You could drill holes in the overflow if it is an internal design so that it doesn't function as an overflow anymore. This would allow it to work just like regular bulkheads into the side of the tank...but be needlessly more complicated.

This.

 

[knobhill]

Lol. Clearly I'm not expressing myself correctly. It must be my 8 week old baby preventing me from sleep!

I understand the physics and mechanics of an internal overflow, and the modifications necessary to run a canister filter through one. So let's forget about those details, they aren't pertinent to my problem...

The issue is hooking up the fx5 to a 3/4" bulkhead for the inlet and 1/2" bulkhead for the return.

How much flow will I lose? Is this bad for the motor? Those are the main issues I don't have enough info to make an informed decision on.

Thanks Fish Eat Fish for the overflow suggestion. Hopefully you have some knowledge that will help me out with the pipe sizing and flow rates

 

[Fish Eat Fish]

It's really not possible to say. The flow rate will be lower than advertised right out of the box for one. It also depends on the length of your hose. If the configuration of the input and outputs is correct for a canister in terms of water levels I can't imagine it would hurt it. You said the outputs are three .5"? That helps assuming the hose that connects them is of larger diameter. If you can't change the bulkheads I would definitely change the plumbing behind them to match the canister hose diameter (I don't remember what it is off hand even having used an fx5). If you run 1-1.5" hose and pipe to the 3 .5" outputs that will ensure that they can split the pressure versus having to run all the flow through a .5" pipe at any point.

 

[Fish Eat Fish]

Pictures would help immensely, but even so I don't think you can easily calculate the flow. That depends on too many factors we don't know. The shape and type of impeller would even need to be considered!

 

[knobhill]

Thanks. I'm just gonna go for it. Also, I read some pretty good info on theplantedtank forum as well.

Look for pics when I do the 140g build thread! That should start happening in a week or so.

 

[SeanPrice]

Any updates on this knobhill?

I am in the process of plumbing & using one FX6 per 1" drain & 3/4" return in my overflow box of a 180 Gallon acrylic tank with center overflow box that has two drains and two returns.