Weir style PVC DIY overflow questions "issues"

[wickette]

I've made a few DIY HOB overflows. Homemade variation of Eshopps/box style overflow work great. I really want a functions King of DIY's PVC Overflow. I've got 2 issues.

1) In his video he starts the prime by pouring water in the air pipe, Ive tried that at least 100 times on different versions, it never works, I cant even wrap my head around how it could work, wouldn't air get trapped at the upper point of over the over flow and prevent a siphon from forming everytime.

2) Aside from having to prime by sucking air out, Ive got this design to work with pipe diameters of 1/4", 1/2", 3/4". its finicky with 1", but using 1.25" and 1.5" pipe the siphon holds if I slowly turn down the the return flow, but siphon breaks when the return is shut off abruptly (simulated power outage). I know it has something to do with the flow/volume of water in the overflow, not sure what the solution is.
I think mounting the T-connector outlet higher, or making the pipe the water moves down longer, making the outlet/drain pipe narrower might all work, but I want a solution that would have the smallest impact of flow rate. Any ideas?
Testing without cementing the connectors is useless, making every version will get expensive.

 

[cymaster007]

@wickette he is using an old design with larger PVC pipes- check out the concept it should help you better -

 

[wickette]

@wickette he is using an old design with larger PVC pipes- check out the concept it should help you better...

Appreciate the attempt, but Ive seen this video, I don't see a connection between that design and how adding water down the outlet end are similar in either issue. This is what I see happening with Joey's priming method:

The video is more like dropping the overflow into the tank to get water surging up the intake.


As for the second issue, with the higher flow of a larger diameter pipe, when it stops abruptly, you can see the water level go down in the weir then get a 'glug' of air get sucked down the , siphon break and weir back fills with water. Water doesn't move hast enough in a smaller diameter pipe to suck air into the siphon flow. (using 3 equal 21" sections of pipe instead of 12" didn't make any noticeable change)

 

[Vwluv10338]

I followed the design of the King of DIY and have the same issues. One thing I found was that I had to put a cap on the taller air tube before opening the valve to start the siphon. With a cap on it will siphon. The second issue I have then is I have a 2x larger pipe in the aquarium but once the siphon flows it will siphon that out quicker than the water can refill and it will break the siphon. He mentioned that you may have to adjust your teeth or holes cut into that pipe which I did multiple times and it just changed my water height and not the amount of flow. So far the only thing that worked was using the valve on the drain to close it down to slow the drain. It’s a pain and I wish I had just spent the money and drilled the tank.

 

[Sisterlimonpot]

The trapped air is your issue, that's such a primitive overflow prone for many problems, which you are learning first hand. Although it's great to play with it, I guarantee you will abandon this type and go with a more traditional way of doing it.

 

[wickette]

Tried this a few times it eventually sort of worked, it got a slow trickling siphon, like what you get when some air is tripped at the top of the tube.

I believe the teeth adjustment is just to make sure you're filtering off the water surface and not a few inches bellow it, it won't change the actual flow without breaking the siphon.

I bought my tanks long before I considered overflow filtration. I've got a lot of tanks up to 90 gallons. the only ones that aren't made from tempered glass are 20 gallons and under. Drilling isnt an option with cheap petco tanks.

The trapped air is your issue, that's such a primitive overflow prone for many problems, which you are learning first hand. Although it's great to play with it, I guarantee you will abandon this type and go with a more traditional way of doing it.

What do you mean by more traditional?

my current over flow is a reverse engineered the eshopps over flow box
2 breeder boxes (one hanging on the outside and the other inside the tank as a weir). and a four U-tubes made from of clear 5/8" poly tubing.

It's never broken its siphon in the 15months its been running, but if it does it wouldn't start back up on its own.

Im retaking up this project after abandoning it for over a year (downtime from the coronavirus lock-down) You seem to be right, this version blows. In the video it looks more reliable than my contraption.

 

[Sisterlimonpot]

The more traditional meaning a more reliable design. I don't know too many tanks that have tempered side glass, especially from petco, (tempered glass cost more).

To rely on a siphon to transfer water up and over the glass is destined for problems. Sure there's ways to lower the risk of breaking the siphon, but to me, I don't view that form of overflow a long term or permanent design.

Theres some clever ways to determine tempered vs non tempered. I personally would never use that type of overflow.

 

[WVNed]

Appreciate the attempt, but Ive seen this video, I don't see a connection between that design and how adding water down the outlet end are similar in either issue. This is what I see happening with Joey's priming method:

The video is more like dropping the overflow into the tank to get water surging up the intake.


As for the second issue, with the higher flow of a larger diameter pipe, when it stops abruptly, you can see the water level go down in the weir then get a 'glug' of air get sucked down the , siphon break and weir back fills with water. Water doesn't move hast enough in a smaller diameter pipe to suck air into the siphon flow. (using 3 equal 21" sections of pipe instead of 12" didn't make any noticeable change)

If you move your outlet to only about an 1nch below the water level in the front behind the weir it will work fine.

 

[wickette]

I don't know too many tanks that have tempered side glass, especially from petco, (tempered glass cost more)...
...Theres some clever ways to determine tempered vs non tempered. I personally would never use that type of overflow.

Tempered glass does costs more, but the glass itself is a tiny fraction of manufacturing cost. its cheaper for companies like aqueon and tetra to mass produce everything using 1/4" tempered glass.

Its pretty easy to tell apart with a $10 pair of polarized sunglasses. I have a very old non-branded 50 gallon from that late 90's with normal glass sides, all of my Aqueon tanks and my larger tetra tanks down to 29g have all tempered sides.
All of them are from the last 6 years all of them from $1/gal sales.

Im sure both companies still make paneled tank, but I havent seen them.

 

[Ratherbeflyen]

It doesn't matter if you build or buy a siphon, or hang on overflow, it's almost a guarantee that the siphon will break and not restart automatically. There is just no way that water will reliably flow uphill if the siphon is broken. My suggestion would be to get an aqualifter pump. It can pump both air and water. If you make an airtight hole, or better yet a threaded barb at the top of the overflow attached to the aqualifter, the pump will come on when the power comes back to pump out any air in the system. That will restart the siphon automatically if the power goes out. The rest of the time it will just pump a couple gallons of water anywhere you want.

This is a way more reliable method. You can even get some commercially available overflows that come with an aqualifter. The downside is the siphon will not restart if the aqualifter fails.

Aqua Lifter Vacuum Pump

Aqua Lifter Vacuum Pump’s unique design lifts water with its diaphragm and flappers – pumping water up to 30” high and at a flow rate of 3½ gallons per hour. Ideal for use as a dosing pump for Kalkwasser, auto top offs, calcium reactors and other aquarium uses. The Aqua Lifter Vacuum Pump is...

www.bulkreefsupply.com

 

[Jo Seph]

The King of DiY upgraded overflow/weir has been working for me for years. To start the siphon I just dunked the whole thing in my tank, capped the bottom pipe, then moved it into place and removed the cap. Siphon hasn’t broken once after many power outages.

 

[Firemike]

The King of DiY upgraded overflow/weir has been working for me for years. To start the siphon I just dunked the whole thing in my tank, capped the bottom pipe, then moved it into place and removed the cap. Siphon hasn’t broken once after many power outages.

I’ve been working through the design of this with a 3” weir and 1 1/2 overflow and can get more than a trickle. What sizes are you using? I’m considering going to a 4” weir to try to get more flow around the overflow. Thanks!