DIY PVC overflow problem

F

fishhugger

Guest
I built a pvc overflow pretty matching this design. http://www.youtube.com/watch?v=kjSLPVoLIs4
The differences: I used 1/2" pvc, the the 3 tubes that are about the same size, are about 10" in length on mine, the longer tube outside of the tank is only about 1-2" above the two elbows that sit above the tank, and any place where two elbows meet on mine are only connected by about a 1" PVC segment, so the elbows touch.
My problem is that when I tested it out in the same manner shown in the video. my flow is really really low. The only thing I can guess, is that because I drilled the hole for the check valve in the center of the two elbows exactly without gluing it together first is causing enough air to get in to lose the flow rate, but not enough to break the siphon. I know its not airtight now, but its fairly close, I just didnt expect it to suck that much in a test run.
I read you can expect around 600gph on a 1" tube and I need around 250ish, is that reasonable for a 1/2" overflow?
 

2quills

Well-Known Member
I would sugguest stepping up to 3/4" pipe for the overflow. Believe it or not 1/2" pipe only has 1/4 of the flow capacity that 1" pipe does. Are you using the aqua lifter pump as well? I can tell you from experience that the check valves will leak air. It's not alot of air but it's enough to slow down the syphon if you're not running the pump on it. What I did on mine was install air line connectors and siliconed them in and then connected the two of them to the aqua lifter pump.
But I would step up to 3/4" pipe for sure.


 
F

fishhugger

Guest
Ugh, I was going to go 3/4" but I could not find a 3/4" union piece.
I am not use the aqualifter, but I had the thought that if after I primed the tube with the check valve, I could attach a small segment of vinyl tube to it, and place another check valve above that in the reverse direction, any thoughts on that?
Regardless of what the flowrate should be, it should not be as slow as it was.
I dont know if I want to start over or not with 3/4", because I want the overflow to flow into a turf scrubber. I know that you should have 35x[width of screen]=recommended gph, but I was thinking if I adjust the size of the screen, it might still work decently. Obviously not up to par with what it could be, but still good. I know I might be wrong there, but that's why I am here....to learn.
 

2quills

Well-Known Member
Quote:
Originally Posted by FishHugger http:///forum/thread/382553/diy-pvc-overflow-problem#post_3339456
Ugh, I was going to go 3/4" but I could not find a 3/4" union piece.
I am not use the aqualifter, but I had the thought that if after I primed the tube with the check valve, I could attach a small segment of vinyl tube to it, and place another check valve above that in the reverse direction, any thoughts on that?
Regardless of what the flowrate should be, it should not be as slow as it was.
I dont know if I want to start over or not with 3/4", because I want the overflow to flow into a turf scrubber. I know that you should have 35x[width of screen]=recommended gph, but I was thinking if I adjust the size of the screen, it might still work decently. Obviously not up to par with what it could be, but still good. I know I might be wrong there, but that's why I am here....to learn.
Yeah the aqua lifter makes priming a breeze. A check valve in the reverse direction really wouldn't do anything but two check valves in the same direction would be better. Which ever one you have connected to the pvc I would make sure to silicone it in otherwise air is going to leak in. Air getting into the pipe is most deffinately the reason why it would be draining so slow in the first place. The trick with these overflows is to have them 100% air proof. The aqua lifter you can leave running on it and it will continously pull out any air that builds up in there over time.
 
F

fishhugger

Guest
I had the wrong idea when you said the check valves leaked air, but I did realize after assembling it that if the intake tube filled up too quickly it would cause alot of bubbles, I think an elbow at the drain level would really help out but I dont know by how much though...can anyone say from experience?
But more about the device itself assembled....I didnt bother returning the peices, because I only spend 6 or so bucks in fittings, the killer was the 2' sections of 1/2" pvc that I had already cut and couldn't return, and the 10' of 1/2" vinyl hose...so I just put it together. All in all, despite not have the check valve siliconed in place yet, it worked really well once I got the fittings cemented in place, if I could reduce the amount of bubbles getting into the tube from filling up to quickly, since it is a really narrow tube, it would be a really great piece for a 10 or 20 gallon tank.
The 1/4th flow of a 1" over flow was a bit overestimated =P. In about 5 or 6 attempts I filled up a 1 gallon jug at about an average of 37 seconds, it was pretty consistent; so that translates into 95-100gph (if I'm not mistaken), and keep in mind that's without any suction helping it out.
Funny story....you know how we (at least me) generally disregard the warning labels of potentially hazardous materials? Well I decided to cement my fittings together down in my basement. It took a C clamp and quite a bit of elbow grease to get the container open....and when I did that stuff nearly knocked me on the ground. I looked over at the wood burning stove and thought to myself '....ehhh...I think I am going to take this outside and suffer the 20 degree weather, rather then burn my parents house down..." =D
 

2quills

Well-Known Member
Quote:
Originally Posted by FishHugger http:///forum/thread/382553/diy-pvc-overflow-problem#post_3339524
I had the wrong idea when you said the check valves leaked air, but I did realize after assembling it that if the intake tube filled up too quickly it would cause alot of bubbles, I think an elbow at the drain level would really help out but I dont know by how much though...can anyone say from experience?
But more about the device itself assembled....I didnt bother returning the peices, because I only spend 6 or so bucks in fittings, the killer was the 2' sections of 1/2" pvc that I had already cut and couldn't return, and the 10' of 1/2" vinyl hose...so I just put it together. All in all, despite not have the check valve siliconed in place yet, it worked really well once I got the fittings cemented in place, if I could reduce the amount of bubbles getting into the tube from filling up to quickly, since it is a really narrow tube, it would be a really great piece for a 10 or 20 gallon tank.
The 1/4th flow of a 1" over flow was a bit overestimated =P. In about 5 or 6 attempts I filled up a 1 gallon jug at about an average of 37 seconds, it was pretty consistent; so that translates into 95-100gph (if I'm not mistaken), and keep in mind that's without any suction helping it out.
Funny story....you know how we (at least me) generally disregard the warning labels of potentially hazardous materials? Well I decided to cement my fittings together down in my basement. It took a C clamp and quite a bit of elbow grease to get the container open....and when I did that stuff nearly knocked me on the ground. I looked over at the wood burning stove and thought to myself '....ehhh...I think I am going to take this outside and suffer the 20 degree weather, rather then burn my parents house down..." =D
Gotta be careful!
Umm...I'm confused. In your first post you said that you could expect approximately 600GPH from a 1" overflow. And by my calculations you're getting 97GPH. So the 1/4 rate was an over estimate? I thought you were looking for 250GPH? A suction pump will pull out any trapped air that builds up in the pipe over time which slows the flow down more and more over time. How would suction increase the drainage by more than a 100GPH?
 
F

fishhugger

Guest
=P
As far as the over estimate thing goes, sorry, that was just me being stupid. I work overnights and havent slept yet, so I was thinking 1/4th of 600 to be 200. >.<.... but yeah its 150 so its not far off.
When I said suction, I wasnt talking about a the suction pump. I meant the PVC or vinyl tubing that would divert the overflowing water down to the sump or scrubber, or whatever you have under your tank, which for me would be between 3' and 4'.....also I just realized that since the longer tube on the overflow lets air in, the drain pipe or tube would have no effect on the rate that water flows through the overflow.....I should go to bed now >.<
And yes, I am looking for 250gph, which is why I said the 1/2" pvc overflow would be great for a 10gallon tank. I am going to have to move up to either 3/4ths or 1" for my 55.
 

2quills

Well-Known Member
Well the most important thing (or one of the most important things I should say) that is going to determine how much water drains is the size of the pump that is pushing water back into the tank. Even if you had a 2" drain on there, it's only going to drain as much water as is being pumped into it.
Are you going to do just a turf scrubber or do you plan on running a skimmer or anything else down there?
 
F

fishhugger

Guest
You might want to reread the post before your last one because I edited to fix my mistakes and you replied fast so you may not have seen it =P....nothing major, just trying to sound like less of an idiot.
But yeah, I understand that about the overflow only flowing as fast as the return pump. I had just thought that the 1/2" would be substantial enough for my needs because I was having a hard time finding answers about the flow rate. And like I said I my plan was to do 3/4ths....but after not being able to get all the fittings in that size and having a dozen+ different size converters, I had decided to downsize. So I think I will be going with a 1" PVC, with a mag-5 or 3 return pump.
The only thing I am planning is a turf scrubber, and then just enough water so I can move my heater out of my DT.
 

2quills

Well-Known Member
Gotcha!
That's cool, a 1" line would be a safe bet for either of those pumps. Keep us posted.
 
Top