pvc overflow questions, please!!

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Feeder Fish
MFK Member
Jul 25, 2009
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Iowa
hey guys and gals. i made my first diy pvc overflow today ive got the overflow made real well. im just having a few problems. also ive read all the stickys here and on many other sites, but i still have questions...

heres the set up:

65 gallon aquarium
15 gallon sump (15 @ 3/4's full)
450 gph pond pump

from the tank into the overflow i used 3/4'' pvc. for some reason i had the idea that it would work fine against the 450 gph pump. the overflow then goes into 1 inch (outer diameter) and into the sump. the pond pump goes into the tank via 1/2 inch tubing.


the problem that i have is when i turn the pump on, my overflow cant keep up with it. the water level rises and i have to abort the process. water funnels into the overflow but when it comes out of the end of the overflow and down the clear tubing, its only a small amount.


a few questions:

1. at 450 gph, my pump should have around 300 gph with a 3-4 foot head, correct?

2. the pipe sizing chart stickied on this site says that the maximum vertical flow for 3/4 inch pvc is 337.5 (fairly close to the pumps rate), but many sites say 3/4 is ok, and some even use 1/2 inch. do i need to bump up to 1 inch diameter pvc?

3. air check valve. i glued one on the top u tube. did i need to? when i start the overflow i place my hand on the air intake and suck from the to-sump tube. when i keep my hand on the air intake, the syphon goes a little faster. when i take my hand away, it goes back to reduced flow. why is this?

4. does the 1 inch tube coming from the overflow into the sump need to be smaller? im pretty sure its 3/4 inch inner diameter and 1 inch outer, so this is equal to my pvc. im just concerned about this tube being too wide and not letting gravity pull the water through.



im sorry guys this was a long one. ive spent all day watching youtube, surfing google, and reading this site for answeres. ive got a lot done but am not satisfied yet, will probably lose sleep over the whole thing until i get it working the way i want it. thanks for any help!!
 
ok, thanks. ill check those rates.

does a 3/4 inch diameter overflow seem about right for a 450 gph @ 1'


so do i need to keep a cap on the "air intake" what would happen if i did?


also, when i put an airline tubing in to stop the gurgeling sound, it cuts the overflow rate down a lot. do i just need to get a 1 inch overflow instead?



edit: i checked the pipe sizing and flow rate sticky again and i have the one that applies vertical flow rates.
 
bitteraspects;3604413; said:
pics of the overflow.

i have a rio1700 running at about 400gph (after factoring in pump head) with a 3/4" overflow, and it runs fine. so it may be a problem with your overflow.

did you follow the design in the sticky?
loops all in the right place?
check valve installed?
pipes all sealed/ no air leaks in the plumbing?
Click to expand...


sry no pics...its the very average design - heres what it looks like. thanks g00gl3 http://media.photobucket.com/image/diy pvc overflow/bulldogg77/diy-overflow.jpg



the pipes arent glued yet because i didnt want to mess anything up until i knew exactly how i wanted it.


im going to hopefuly leave for home depot soon...that would be nice if i didnt have buy another one...im just terrified of something overflowing. i wonder if it being glued will make it work.

like i said before, last night i had it running for tests and it kept up with it until i put the darn airline tubing in to stop the gurgling sound. then the flow in the tank started to raise way above the inlet to the overflow. arggggg this is really nawwing at my brain!
 
without a picture of your overflow, its hard to say. i know what the design is supposed to look like, but unless yours is exactly the same, it doesn't necessarily matter.

if your pipes arent glued, you could have small air leaks there, which would slow the flow of the pipe
if your check valve was not properly installed/ sealed, air will leak in there (if you have a check valve installed)
if your check valve was installed properly, but you didnt suck out the excess air in that bend of the tube, that would slow the flow


a picture of your overflow would really be more help.
 
also can someone answer my question about puting a cap on the high air intake tube? the thing works real well when i put my hand over it
 
k thank you very much! i got the 3/4'' overflow up and running now.

the only other question i can think of is about the syphon. i do not want to have the syphon break and my 55 flood my bedroom. i was thinking about an airlifter. can the airlifter go onto the check air valve via airline tubing? is this 99.9-100% assurance that i will not be flooded? i want to be able to leave it and forget it (until cleaning of course). right now id like to go to the hardware store or fishing but am worried about my setup for now.
 
there is no such thing as 100% assurance on any system or filter. canisters can leak, pumps can burn out, power can go out, etc.

you can go with an aqualifter for added protection, or attach the airline ot a powerhead in the tank. as long as your overflow is properly set up and sealed, you shouldnt have any problems. there are many people here who have been running PVC overflows with no problems for years.

otherwise you can just drill your tank. a hole saw is cheap on ebay, and drilling the tank will remove the potential cavitation problems of a PVC overflow. but like i said, a properly built overflow should not have any problems.
 
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