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Discussion Starter · #1 ·
I have a Fluval 405 canister filter. I've read that it outputs 340 to 400 GPH. It is hooked up to my 75g tank. What I was thinking about doing is getting 2 pieces of 1" clear acrylic pipe (20" long) and drilling 1/2" holes, about 1" apart, down the length on two sides. I would splint the filter return line into to lines and attach the ends to the acrylic pipe, capping the oposite end. The pipes would then be placed in the 2 rear corners of the tank with one line of 1/2" holes faceing along the back of the tank and the other row faceing along the side of the tank. If it works, it would creat excelent water movement throughout the tank.
My questions are, does the Fluval have enouph output power to allow me to split the return line into two? Will the design of the 2 1" pipes work like I want it to and distribute the water evenly out of all of the 1/2" holes? And, assuming I cant split the return line into 2, will this work with only one 1" pipe hooked up to the one return line?
I realize there might not be any spicific answers to these questions, but I was wondering if there were any expert speculations. Thanks.
 

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I use a Magnum 350 (350 GPH) on my 50G and I made a DIY 4' spray bar with 3/4" PVC. I used 3/4" PVC because the tubing size for the Magnum 350 is 5/8" and it was a very close match to the inside diameter.

I drilled 1/4" holes every 4 inches or so and the pressure is just high enough to move enough water to keep free of dead spots.

Knowing that, I think you will lose way too much pressure to keep good flow. Splitting the output will reduce pressure/flow, then running it into 1" pipes will further allow a pressure/flow reduction. The holes being 1/2" will definitely lower pressure.

What I mean to say is that the volume will likely remain the same, but the pressure of what is being pushed out will be too low to move water all the way across the tank. Imagine blowing through a straw as hard as you can, then blowing through 2 straws side by side as hard as you can. The same *amount* comes out the other end, just with much less force.


Edit: forgot to add a possible solution:

1. Use a pair of pipes whos combined inside diameter matches or is just a little larger than that of your outlet hose. (ex. 1' outlet hose split into to 1/2" or 3/4" pipes.)
2. Drill smaller holes in the pipes to keep the exiting water moving under higher pressure and speed.

Remember if you start with smaller holes and the water is moving too fast you can always go bigger after testing it, but you can't go smaller once a 1/2" hole is drilled.
 

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Discussion Starter · #3 ·
Got you. I picked those sizes cause I did'nt want the opposite to happen; to MUCH pressure causing a backup into the filter. So, you think the concept will work but the sizes have to be re-vamped? Is this all a "trial and error" kind of thing? Or could I say that if I reduced the pipes to 1/2" and the drilled holes to 1/4" or 1/8", it will work?
 

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It sounds like a great idea to me but I agree with what DevinWolfe said. I think I would start with something as small as 1/8" holes in 1/2" pipe and go up from there. PVC is relatively cheap you could try several prototypes and see what works best then build the final one out of the clear acrylic.
 

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It will definitely work with proper pipe and hole sizes. Lots of people on here make their own spray bars and get really nice flow. I searched for threads when I was making my own but did not keep the list I had for reference.

I would honestly just use a 3/4" O.D. PVC because it's I.D. will be close to that of your return line. I would start with 1/8." just to be safe, because I think the fact that the output will be split will have a significant affect on the pressure of the water inside the pipes.
 

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Discussion Starter · #6 ·
Thats a great idea. I can practice with the regular PVC. As far as the splitting the return line and making 2 sprayers, do you guys think it will cause too much of a pressure drop? Should I just stick with one sprayer and one return line?
 

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Something I didn't think about until now is that PVC is usually schedule 40. That is pretty thick for a 1/2" or 3/4" pipe. I have never worked with acrylic but if someone else has I am sure they could advise you as to the wall thickness. You may be better off stepping straight down to 1/2" instead of 3/4" like I had originally said.

The image below is what I had leftover from my Rex style reactor and spray bar - thats 3/4" PVC inside of 2" PVC so you can see the relative wall thickness.

 

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I just made a DIY spraybar for a fluval 405 this past weekend. I used 1/2" schedule 80 PVC from Lowe's. They have this stuff in stock in a dark gray color. Also, the beauty of it is that they sell this PVC pre-threaded and the pre-threaded end fits perfectly into the end of a standard fluval ribbed hose.
 

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Something I didn't think about until now is that PVC is usually schedule 40. That is pretty thick for a 1/2" or 3/4" pipe. I have never worked with acrylic but if someone else has I am sure they could advise you as to the wall thickness. You may be better off stepping straight down to 1/2" instead of 3/4" like I had originally said.

The image below is what I had leftover from my Rex style reactor and spray bar - thats 3/4" PVC inside of 2" PVC so you can see the relative wall thickness.



FTI - you can use "thin wall" pipe- its called SDR and works with sched 40 & schedule 80. ID is way larger than standard ¾"pv
c
 

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Just a couple points of reference. Schedule 40 1/2" PVC has an internal diameter of 0.622 (5/8=0.625) so using 3/4 is overkill. The reason 5/8 hose is used is for the Barb fittings. Typically on canister filters with 5/8 fittings the actual hard plumbing, both inside the canister and standard included spray bars is nearly right on 1/2 or 0.500. Your Initial design would have far to much pressure drop, resulting in extremely low velocity from the spray bar (high volume) which would mean very poor flow in-tank. (Scale up if tubing is 3/4 or 1")

What I would recommend is you start by using a pressure drop calculator like this Pressure Drop Online-Calculator . First measure the actual ID of your filter orifice and included returns. Then calculate the pressure drop based on the unrestricted flow rate of your pump. No need to include head height in your pressure calculation because a canister is on a siphon so head is negligible (1-5"). Then calculate pressure drop across your proposed designs. As long as the spray bar is significantly larger ID than the fixed orifices in your filter then there won't be enough length to add to pressure drop. For instance internal pump may be 0.542 and internal 1/2pvc is 0.622 that is a very significant difference and won't effect pressure drop. So what you want to calculate is the drop across all the individual spray bar holes against their length (0.109" for 1/2pvc). Be careful with hose Barbs!! I have many varieties from many manufacturers and the internal diameter on hose Barbs is no consistent, and always much smaller than hose ID. Hose Barb orifice diameter is a large contribution to this equation. An alternative is to use 3/4" Barb's and heat/stretch 5/8 tube over them.

I would start by aiming for a much higher pressure drop initially, because you can always add more holes. I don't mean this to be an exact science, but it can go you a very good Idea on how many/how big of holes to use. I have made alot of PVC returns, once you get a ballpark idea and a feel for it you won't need all the math. That calculation makes it very fast though. If you need help with putting in or interpreting the numbers let me know.

Wow, did not notice this was a necro post ...
 
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