pvc overflow problem

[h20addict]

I built a diy pvc overflow for my frag tank and have a hard time getting the siphon to start draining or keep.draining. Its very sparatic

 

[Mebbid]

Could you take a picture of the other side? From here it doesn't look like you should have a problem

 

[h20addict]

Not the beat pictures, but all i have untill i get back to the tank

 

[Airgoose2222]

From the pics, it looks like the hole where the airline tube is isn't sealed. If there's air escaping in through there, you'll never have a siphon. It needs to be siliconed.

 

[Airgoose2222]

Looking again, is there a hole drilled on that end cap on the taller tube outside the tank? If not, there needs to be one for air to escape. Even if you silicone the tube, that will impact the siphon as well.

 

[h20addict]

There is a hole on the end cap.now,
I was told not to silicone down the airline incase i needed to move it up or down.the back side of the overflow

 

[Dav3]

Actually what you need to do is glue an airline check valve(walmart or any lfs should have these) in the hole where the airline tube is. This will prevent air from being sucked into that U tube section. Then attach the airline to the check valve so you can pull the air out to start the siphon. Make sure you have the check valve in the right direction.

 

[h20addict]

The airline already has a check valve on the end already. Do i.need to.silicone the airline hose around the pvc

 

[Dav3]

You want the check valve glued directly to the PVC. You don't want any air gaps in that U tube going over the lip of the tank. Air in there breaks the siphon.

Edit: basically you want the whole thing to be air tight from the inlet to the T where the vertical air gap pipe with end cap is. That whole section needs to be air tight.

 

[h20addict]

Ok, so slide the airline all.the way down a.d superglue the check valve to the pvc.
Or silicone the check valve to the airling and leave airline still extended but silicone around the hole in the pvc so i dont have to bang my head on.the wall to suck on the check valve.

Will having it not cemented together cause the same issue

 

[Dav3]

Rip out the airline tube. You don't want any airline inside this section of the PVC. Put check valve end(part airline slips over) in hole. Seal check valve in place. Then attach airline to other end of check valve. And you are done.

Ideally you want the check valve to be at the highest point internally of that U tube section. Based on the picture it looks like that spot is on the other elbow because it is leaning back a bit.

 

[h20addict]

So can i just swap the elbows with the holes to have the check valve hole on the in tank side?

 

[h20addict]

And can i get away with gel superglue or do.i .eed to silicone it

 

[Dav3]

You can if it's not all glued together yet. Actually if it's not all glued together I would leave elbows as they are and just shorten the piece between the elbows so the elbows touch each other. This will help eliminate some of the lean.

It's more ideal to have the check valve on the elbow you have it on now as long as it is the highest point or close to it. Air will get pushed/trapped in the top back section on that elbow. Occasionally you can try to suck air out. Or optionally add an aqua lifter pump.

 

[Dav3]

And can i get away with gel superglue or do.i .eed to silicone it

I believe I just used a tiny bit of PVC glue in the hole to bond the two as it melts the plastic together creating a tight seal. Then silicone outside the hole to make sure. I suppose superglue gel will work as well in place of the silicone.

 

[h20addict]

Ok, im going to shorten the top section and.pvc glue in the check valve as mentioned in a few.moments

 

[h20addict]

Check valve side marked out does go on top and.not in.the hole correct

 

[Dav3]

Should have an arrow on it that you want pointing away from PVC. You want to be able to pull air out of the PVC without air going back in. Hence the check valve.

 

[Dav3]

Just a note. 1/2" overflow won't move much water. At least not as much as you would think. Not sure on GPH. You would need to test/measure that.

 

[h20addict]

Still doesn't want to start up. Am i missing sumthing obvious?
I didn't want to glue it till i had it working but im at the end of the road here...