# DIY Canister Question



## car0linab0y (Aug 10, 2009)

Ok... so I looked through a bunch of post about DIY canisters, and most nay-sayers reasoned that most designs would not hold up to pressure. The fact that manufactured canisters that fail tend to shoot water everywhere supports their argument, so I'm not saying they're wrong. BUT... I've been working up a DIY canister design in my head and on paper, and it seems it would have a vacuum instead of positive pressure, so as long as the container has a decent air tight seal in idle state, it would only seal better with the vacuum sucking the lid on tighter.

Any arguments welcome. I want to get it right the first time. A co-worker of mine says if I can make one he'll "contract me out" to make him one too. Once I get the canister design finalized, I have a grand scheme that ties it into an UGF setup.


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## ben1988 (May 2, 2009)

i have heard of people using screw on caps with success as well as glueing PVC together. I am not sure how thye worked the pump and such in to the whoile thing but im pretty sure it would be either a syphon feed with pump return or pump inlet and pump return...


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## R-DUB (Jun 3, 2007)

The only problem that I would see is what type of water pump would "pull" water through filter pads and media under vacuum pressure?? That would take a very specialized pump--$$$$$ Or am I mistaken? :roll: :-?


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## cichlidfeesh (Apr 6, 2009)

Canisters are a closed loop system in order to maintain the water level even with that of the tank. That way the pump doesnt have to deal with pushing water up, like you would see with a sump. This design makes the canister deal with a lot of pressure trying to push the lid off, therefore you would need a strong clamp in order to prevent leaking. I don't see how you would make a vaccum, but if you do please share!


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## KaiserSousay (Nov 2, 2008)

Allot of DIY canister projects are killed off during the research and costing out of the parts. 
Others have got through the $$$, but when the added grief involved in service was figured in, the ideas were either dropped or the developer went with a sump system.

The below will take you to one of the nicer builds I have seen. Might load slow as there are allot of pictures.
http://www.aquaticplantcentral.com/foru ... -step.html


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## PfunMo (Jul 30, 2009)

It's always been a thought that I might want to try building one but It never got far. While money is important when spent upfront, there is also a question of when you want to sell it. To me the time is not terribly important as I am retired and have quite a lot of "spare" time. Even at that, I do not feel it works for me. If one figured a new filter at eighty dollars and somehow was able to built one for half that, It would not work for me. I would have a canister with a gazilion hours spent that most likely would be so ugly that I would guess the resale value as about two dollars.  
Figure in the chance that it might flood and the idea goes out the window. Got lots more important things to do. Like, man, I need to clean that tank again. :-?


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## car0linab0y (Aug 10, 2009)

cichlidfeesh said:


> Canisters are a closed loop system in order to maintain the water level even with that of the tank. That way the pump doesnt have to deal with pushing water up, like you would see with a sump. This design makes the canister deal with a lot of pressure trying to push the lid off, therefore you would need a strong clamp in order to prevent leaking. I don't see how you would make a vaccum, but if you do please share!


My design uses one of my existing powerheads, 290gph with the return hose attached directly to the powerhead discharge, so all the positive pressure would be applied to pushing water through the return, not back into canister. Just seems natural to me (I have some education in physics dealing w/nuclear power too...) that with the powerhead taking suction FROM the canister, but not discharging back TO the canister would create a vacuum.


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## KaiserSousay (Nov 2, 2008)

Build it
Run it
Post it
8) Please 8)


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## car0linab0y (Aug 10, 2009)

KaiserSousay said:


> Build it
> Run it
> Post it
> 8) Please 8)


getting started this week. found a supplier of buckets with o-ring lids for 1.25.


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## Rick_Lindsey (Aug 26, 2002)

I would expect there to be a "vacuum" relative to the tank water, but not the surrounding air.

Just sitting down underneath the tank, there is positive pressure due to the water weight (this is why a siphon works). Pumping the water out of the canister should relieve some of this pressure, but it seems unlikely to relieve enough of it to create a partial vacuum relative to the air.

It should, however, create a lower pressure within the canister as compared to the tank, however, so water will siphon down from the tank to equalize said pressure.

Just my take, and it's been many a year since i studied this sort of stuff in college.

-Rick (the armchair aquarist, who pushes electrons for a living, so he's no hydrodynamics expert)


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## Rick_Lindsey (Aug 26, 2002)

Good news is that positive pressure should help your powerhead pump without seeing the full amount of "head" that a return from a sump would see .

-Rick (the armchair aquarist, who is interested to see the results)


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## car0linab0y (Aug 10, 2009)

Rick_Lindsey said:


> I would expect there to be a "vacuum" relative to the tank water, but not the surrounding air.
> 
> Just sitting down underneath the tank, there is positive pressure due to the water weight (this is why a siphon works). Pumping the water out of the canister should relieve some of this pressure, but it seems unlikely to relieve enough of it to create a partial vacuum relative to the air.
> 
> ...


yeah... I did some thinking after my previous post. I remembered the "fluid pressure height" thing. as long as the tank is above the can there will always be pressure simply due to gravity. I think with my design though, I doubt there will be enough UPWARD pressure to push the lid off and leak.


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## Rick_Lindsey (Aug 26, 2002)

car0linab0y said:


> I think with my design though, I doubt there will be enough UPWARD pressure to push the lid off and leak.


Pressure is pressure, it's pushing out in all directions simultaneouslike, up just as much as down. Depending on your lid retention system, though, you may very well have a low enough pressure to avoid leaks.

-Rick (the armchair aquarist)


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## cichlidfeesh (Apr 6, 2009)

I get what you are saying and all I can add is good luck. I'd be great if the thing works with no problems, and if it doesn't work youâ€™re just out some tubing and a bucket. Are you going to include detachable shut off valves for maintenance? When you turn the pump off watch out for leaks! Also priming might be a challenge, so watch out for leaks then too! Good luck, and be sure to keep us updated!


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## car0linab0y (Aug 10, 2009)

Got buckets, pvc, hove, and valves today. Already had silicone at the house. total spent so far is like $30. Gonna need bigger drill bits, so I estimate another $10. Probably gonna end up getting another powerhead for the internl pump. Thought about using the two 290gph powerheads I have now and feed them both into the return line, but I'd still have to buy another one for circulation inside the tank.

I plan on having intake & return both under gravel btw


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## car0linab0y (Aug 10, 2009)

hit my first snag shortly after getting started yesterday. out of all the things to overlook, I forgot about needing to run the cord for the pump. now, since the end of the plug is way bigger than the cord, any ideas on how to plug that hole? I'm sure I can make a quick cap and silicone it over the hole (from the inside so pressure pushes tighter instead of pushing it out) but just wanted to see what other ideas are out there. inlet, outlet, and priming tube all seem pretty tight so far.


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## cichlidfeesh (Apr 6, 2009)

just cut the cord near the plug and make a hole in the bucket for the cord. After you string the cord through connect the plug back to the cord. Just make sure the connection is water tight.


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## car0linab0y (Aug 10, 2009)

cichlidfeesh said:


> just cut the cord near the plug and make a hole in the bucket for the cord. After you string the cord through connect the plug back to the cord. Just make sure the connection is water tight.


lol too late, I did think of that though. didn't want to lose the integrity of the cord.


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## car0linab0y (Aug 10, 2009)

I've been thinkin about this whole "lid pops off and you come home to an empty tank" thing right... my original idea was to use an overflow style intake, but then I decided on the UGF intake. it dawned on me today that if the lid did come off, the overflow intake would only allow the tank to drain to the level of the intake. however, I still want the UGF. the solution I came up with is to make a small hole in the intake & return tubes near the top of the tank. small enough not to take much away from the suction & return points, but large enough to let air in and break the siphon in the event the lid comes off. what do yall think?


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## PfunMo (Jul 30, 2009)

Not sure if I follow what you propose doing. What I think you say is you are planning a hole in a syphon tube?? Draws air way easier that water so sucks in air and stops pulling water. No hole small enough to work. Correct me if that is not what you meant.


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## car0linab0y (Aug 10, 2009)

the hole will be below the water line, so when the water level falls below the hole (say due to the canister failing) the hole gets air into the tube instead of allowing the whole tank to drain.


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## PfunMo (Jul 30, 2009)

Okay. Now I see the light. I thought I must have missed some vital point there. Good idea for that. I'll go back to sleep now. :zz:


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## car0linab0y (Aug 10, 2009)

First trial run was a success!!!! Inlet leaked a little at the female-female connector, but I hadn't glued it in place yet. Blocked the return line about 2/3 of the way for a few seconds to test the lid and it held. Lid did pop off when I unplugged the pump, but I have a plan (previously mentioned) to stop the tank from draining. I think a few of those thick rubber cords with the hooks on the end (if anybody knows what they're called) should keep the lid on.








This is a shipping bucket with an O-ring in the lid. It's pretty heavy duty, so you have to bang the lid on with a rubber mallet. The pipe with the valve is for priming.


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## PfunMo (Jul 30, 2009)

Bungee cord, maybe?? That's if you use them at the New River Bridge.  
Either way I know the cord you mean. :thumb:


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## PfunMo (Jul 30, 2009)

Another fail-safe fastener for the lid might work. A board across the top and bottom connected up each side with allthread with nuts and washers? Maybe a slotted end of the board and wingnuts to make it easier to remove when needed?


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## car0linab0y (Aug 10, 2009)

PfunMo said:


> Bungee cord, maybe?? That's if you use them at the New River Bridge.
> Either way I know the cord you mean. :thumb:


just didn't want to get them confused with those cheap ones with the strands and the nylon sleeve. I guess those would work too though.


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## fishEH (Sep 15, 2008)

I know you've already built the canister but next time maybe drop a few extra dollars and get a bucket with a screw on locking lid. Great job on the design though and way to prove all the nay-sayers wrong. As for securing the lid I'd go with the board on top and bottom joined with threaded rod.


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## star rider (Mar 20, 2006)

cool. on maint.. you may want to consider some valve/shutoff. so you can do maint and not worry about water from the overflow/inlet.


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## car0linab0y (Aug 10, 2009)

star rider said:


> cool. on maint.. you may want to consider some valve/shutoff. so you can do maint and not worry about water from the overflow/inlet.


I have them, just haven't put them on yet. Realized a little to late I should've put them just above the lid, so they'll be further up.


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## cichlidfeesh (Apr 6, 2009)

So what ever happened to this? Did it end up working out?


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## car0linab0y (Aug 10, 2009)

cichlidfeesh said:


> So what ever happened to this? Did it end up working out?


lol bills came around, so things slowed down on the "new" tank. got the rest of the hose I needed today. looking for my gorilla glue the last 30 minutes to put my suction & return lines in place.


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## car0linab0y (Aug 10, 2009)

Finally got the tank up and running. Can't get a COMPLETE seal where the pipes come through the lid of the canister, but with the holes (mentioned before to keep the tank from draining if the canister fails) in the uptake, it maintains tank level and only air leaks from the canister once the tank level is even with the hole.


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## caseyof99 (Aug 5, 2009)

I built one not too long ago.

http://www.cichlidforum.com/phpBB/viewt ... 84e7e01eb0

I was able to make water tight bulk heads out of pvc fittings. The way mine is setup its not under pressure either. Intake needs to be bigger that outtake.


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