# I solved it! (I hope) Self priming DIY overflow.



## One_Cich_Dude (Feb 2, 2009)

Anyone who has researched the DIY PVC overflows knows that their biggest drawback is the lack of a self priming feature. Over time, bacteria and other organisms colonize the inside of the overflow tubes, and release gasses as these organisms respire.

This requires the user to suck the air (gasses) out using any number of methods. Most common is simply an air hose attached to a check valve at the top of the overflow. Another method is to use an aqualifter pump. Yet another suggestion is to connect the air line to a powerhead venturi.

I tried this with three different powerheads and none of them generated enough suction through their venturi ports to prime the overflow.

Well, the other day I bought a Lee's "Ultimate gravel vac", similar to a python water changer. This device uses a venturi tube to suck water over 25' through a hose from your tank to your sink.

The actual venturi itself can be ordered individually online from most places that carry Lee's aquarium products. The exact same part can be bought as a "Blue magic super pump" for filling and draining waterbeds.

I ordered one online, and it arrived today. I plan to install it on my return line. This way, the flow of water from my sump will automatically prime the overflow using the venturi.

At $6 give or take, It's worth a shot. I just put the finising touches on a DIY background for a 55g. tank, and as soon as the silicone cures in a few days, I'm going to try this out and see if it will work. If it will suck water out of my tank through a 25 foot hose, I think it will be more than adequate to prime an overflow through a 3 foot long air hose.

The only question is whether the flow rate from my pump can generate enough suction through the venturi. If this works, I'll post pictures of the setup in case anyone wants to use it. I'll need to get a few more fittings to adapt PVC to the garden hose threads the venturi uses, but that shouldn't be too hard to cobble together.


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## greenbirds (Jul 30, 2007)

Interesting experiment. Please report back.


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## jwal (Jan 17, 2008)

also, you can use this type of vacuum pump to suck out any air bubbles that may form. it's pretty cheap.

Tom Aqualifter AW-20
http://www.bigalsonline.com/BigAlsUS/ct ... lifterpump


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## cichnesss (Feb 21, 2009)

second on the aqua lifter. thats what i use


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## Charlutz (Mar 13, 2006)

Or you could use a strong enough return pump to push water fast enough through the siphon tubes that it pushes the microbubbles through as well.


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## KaiserSousay (Nov 2, 2008)

Sorry to disagree with ya Bubba,
but a well made pvc overflow does not loose it`s "prime".








The main problem is the noise they make.


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## One_Cich_Dude (Feb 2, 2009)

KaiserSousay said:


> Sorry to disagree with ya Bubba,
> but a well made pvc overflow does not loose it`s "prime".
> 
> The main problem is the noise they make.


Mine don't lose their prime in testing either. But I have read on the MFK forum that eventually certain bacterial sludge builds up inside the pies and while it doesn't significantly impede the flow, those bacteria do respire and give off gasses which can collect at the top of the overflow and eventually break the siphon if the gasses are allowed to accumulate.

If you have a constant suction at the top of the tube, this prevents any gas buildup from the bacteria.










I settled on a hybrid stockman/durso standpipe to reduce the noise. If you tune the flow with a ball valve, you can get the noise down to a level that isn't any louder than an HOB filter.


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## mel_cp6 (Feb 3, 2009)

mine never seem to lose syphon either.
it always starts by themselves once water is at the right level.
after a couple of minutes everything goes back to normal operation.

btw, to significantly reduce the gurgling noise. put a cap and drill a hole on it.
then put an airhose in there until and lower it until its quiet.
its better to put a rigid line and the end of the airline.

kaiser, how does yours work anyways?

mine is similar to one_cich_dude, except in black.
with the black background i dont even notice its there.


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## KaiserSousay (Nov 2, 2008)

> kaiser, how does yours work anyways?


http://www.aquariumlife.net/projects/diy-overflow/120.asp
System worked just fine..just like most all of the PVC overflows do.
Tank being in the living room, noise was the major issue..
Pause.... opcorn: ....Pause
The above is me waiting for the flood of gadgets, gizmos, and do-dads that might get suggested to soften the gurgle 
The second issue was sump size. My stand only allowed for a container that was less then 10ga. The input-output balancing act was a real chore.
After a few weeks I finally pulled it all out and went with canisters.


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## parkayandbutter (Jan 15, 2008)

Dude Just get one of these like I have: http://txholeyrocks.com/catalog/product ... 8eee203f77


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## KaiserSousay (Nov 2, 2008)

> these like I have


Thanx, but no..I agree with bulldogg, the bad stuff I most want to filter is not floating along, waiting to be pulled into the skimmer. The stuff at and near the bottom is what I want. Bulldogg`s skimmerless would be my choice if I were to go back to the land of noise,,yeah, yeah..people, I have heard you..with just this piece of pipe, sponge, yadda-yadda you have got the noise down to a whisper, barely hear it, soothing sounds of rushing water.
All well and good for you :thumb: 
But the deal is, my wife can hear it. 
After she hears it, she lets me hear it....Got it???
If you tell me you have a completley silent HOB overflow, you have a valve adjusting the flow to your sump..other than that..it is making some noise.
How can I say that??
Been there, done that...more than once as I ran accross yet another silencing idea..
Have I givin` up, nope, not yet


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## mel_cp6 (Feb 3, 2009)

just a question for you guys.
i did a priming test today and 1 of my pvc overflow doesnt start draining anymore
after turning on the pump.

actually, i cut this one just recently and installed a new shut off valve but there
is no leak what so ever.

i check the check valve and it looks like its broken because its not 
holding the water. once you prime the drain the water from the airline goes into the check valve.
also if i dont plug the end of the airline the pvc doesnt work. 
for the meantime i installed a screw to cap off the airline and it works for now.

could this be the problem? a broken check valve?
i suggest you guys install a rigid line into the hole so the check valve can be replaced if 
it brakes. this way you dont have to remove the glue/silicone to replace it.

come to think of it, me may not need a check valve but just a rigid airline with a hose attached to it and just cap it off after priming. 
we may also be able to use the line as a pilot drain. just put a long enough air hose and after priming put the end of the airhose below the water line in the tank but also lower 
than the drain hole of the pvc itself. this way there will never be any air in there since water is flowing back to the tank. wonder if this will work.

im going to try on the other side and will let you guys know how it goes.


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## KaiserSousay (Nov 2, 2008)

> remove the glue/silicone to replace it.


I used some brass pipe pieces as "taps" to make threaded holes for threaded plastic/nylon pipe fittings.
No more worries about breaking a seal, to let air in, or water out.
PVC fittings, 90`s, caps, etc. are thick enough to cut threads in.
BTW...When looking for the various components of a HOB/PVC overflow, sump system do yourselves a favor and look at the assortment of fittings available for drip irragation systems..they have some really neat stuff, for cheap.


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