HOB U-tube mod

[DJF]

I am modifying hang on back U-tubes to hook them up to Venturi powerheads. Idea is that will suck any air out of the top and retain the siphon (I miss aqualifters) I have it working fine but wondering if there is anything I can do to improve the suction coming from the u-tube? As it stands now it keeps the air out barely and I’d love to have it be powerful enough to start a siphon from an empty tube. Will a more powerful powerhead create more suction? Currently using a 166gph acela that is hooked to the overflow box near the surface.

 

[exnisstech]

I'm not sure why you need a pump to prevent syphon loss. I've been running hobs for years and the only time I have ever had to remove air was durring initial installation and I did that with an airline hose and sucking myself vs a pump. I have never had one loose syphon.

 

[ScottJ]

I am modifying hang on back U-tubes to hook them up to Venturi powerheads. Idea is that will suck any air out of the top and retain the siphon (I miss aqualifters) I have it working fine but wondering if there is anything I can do to improve the suction coming from the u-tube? As it stands now it keeps the air out barely and I’d love to have it be powerful enough to start a siphon from an empty tube. Will a more powerful powerhead create more suction? Currently using a 166gph acela that is hooked to the overflow box near the surface.

I use a LifeReef overflow and haven't had any air build up at the top of the tube. Is your flow high enough? I notice that air bubbles just get sucked right through the tube.

Would love to see a picture of your mod.

 

[DJF]

I hear you and so have I. It’s an extra layer of protection. I have had air collect at the top of the tube and do on occasion lose siphon in one of the 2 tubes in the overflow (eshopps p1200). Basically I believe it’s due to not enough flow for both tubes (so the air bubbles don’t push all the way out and rise to the top of the utube. I’m a redundancy guy so you won’t convince me to run just one utube. I want to bullet proof the setup ahead of a scheduled vac. CPR makes (or maybe made) a version with an aqualifter to help; that’s what I’m trying to emulate, just want a touch more suction from the Venturi.

 

[DJF]

I hear you and so have I. It’s an extra layer of protection. I have had air collect at the top of the tube and do on occasion lose siphon in one of the 2 tubes in the overflow (eshopps p1200). Basically I believe it’s due to not enough flow for both tubes (so the air bubbles don’t push all the way out and rise to the top of the utube. I’m a redundancy guy so you won’t convince me to run just one utube. I want to bullet proof the setup ahead of a scheduled vac. CPR makes (or maybe made) a version with an aqualifter to help; that’s what I’m trying to emulate, just want a touch more suction from the Venturi.

Here is the first tank I’m experimenting on… right now the 2 tubes are Y’d to the 1 venturi…. The suction seems about the same when I run 1 or both. The tube with the elbow is my first correction to try and lower the height/head. I
Current plan is to either Y the other 2 together on another pump.

 

[Snoopy 67]

The flow MUST be able to pull any bubble completely out of the tube -PERIOD- or eventually you will loose siphon.
Ran dual overflows on a 220 for years & never had a problem as long as flow was there.

 

[TheSheff]

I'm not sure why you need a pump to prevent syphon loss. I've been running hobs for years and the only time I have ever had to remove air was durring initial installation and I did that with an airline hose and sucking myself vs a pump. I have never had one loose syphon.

I ran the eshopps hob for a while. The only thing that causes bubbles is too low flow.

 

[exnisstech]

I’m a redundancy guy so you won’t convince me to run just one utube. I want to bullet proof the setup ahead of a scheduled vac.

I think a better redundancy would be to correct whatever you need to that will prevent a syphon loss. Ive had two of these running on a 180 for over 5 years and have never lost syphon even with the return pump turned off and draining water out of the DT.

 

[TheSheff]

I think a better redundancy would be to correct whatever you need to that will prevent a syphon loss. Ive had two of these running on a 180 for over 5 years and have never lost syphon even with the return pump turned off and draining water out of the DT.

as long as water is covering both ends of the u-tube(s), than there is no risk of losing syphon.

 

[DJF]

Agree on the lack of flow being the issue. I can address by going down to one tube but to me they feels unsafe. How I’m hoping to address is to get the air out by the powerhead as it rises and keep the redundant tubes. I can go down to one and it is generally reliable

 

[DJF]

as long as water is covering both ends of the u-tube(s), than there is no risk of losing syphon.

Almost always true unless enough air collects at the top of the tube and there is not enough flow to push it out

 

[exnisstech]

as long as water is covering both ends of the u-tube(s), than there is no risk of losing syphon.

Agreed that's why I don't understand the OP need for a pump to remove air

 

[Crustaceon]

You have to have enough return pump flow to blow the bubble out of the tube. It sounds sketchy, but it’s FAR more reliable to use a higher flow pump with a siphon overflow box than a lower flow one so long as you avoid exceeding the box’s flow rate. I run a siphon overflow on a 20g display with a 317gph lifegard pump. I can blow a steady stream of bubbles directly into the siphon tube and the momentum of the water entering it pushes the bubbles out instantly. Also make sure to keep your drain lines close to the water surface of your sump (1/2”). You want your drains flowing at a consistent rate, so avoiding any trapped air in those drain lines is the goal. I can shut my return pump off to simulate a blackout, turn it back on after ten minutes and it’ll restart and stabilize within ten seconds like nothing ever happened.

 

[exnisstech]

Almost always true unless enough air collects at the top of the tube and there is not enough flow to push it out

Air can not collect unless you do now have enough flow as stated. Increasing flow would be the solution not adding a pump. JMO

Edit : I reread your post where you state it's OK with one tube but you want to run two. I guess if that works for you then it works. Personally I would risk a blockage (which I've never had) vs risking a syphon break if a pump fails etc but we all have different risk factors.
EDIT I'm also fortunate in that my return chamber would run dry before the tank overflows even if my return tubes become blocked or a syphon is lost. Might cost me a pump but cheaper than a flood. All of my sumps have been set up that way even my drilled tanks. I keep the level in the return chamber just high enough to prevent air entering the pump.

 

[DJF]

Air can not collect unless you do now have enough flow as stated. Increasing flow would be the solution not adding a pump. JMO

Edit : I reread your post where you state it's OK with one tube but you want to run two. I guess if that works for you then it works. Personally I would risk a blockage (which I've never had) vs risking a syphon break if a pump fails etc but we all have different risk factors.

Thanks. I appreciate all the feedback- Thankfully if the pump fails I don’t lose siphon. But it is a good point that it’s another spot where things can fail. To be honest I’m surprised the mod isn’t done more often- It’s not anything new and is a feature of some hobs- if the consensus is that it’s safer to run without a siphon starter on redundant tubes then I can accept that.


My original question is if a Venturi powerhead’s gph matters to the amount of air suction it creates. Would a 300gph powerhead have more air intake than a 150gph powerhead?

 

[DJF]

fwiw I changed the design and added a backflow valve inline at the top… at minimum I can just connect a tube to the top to manually start the siphon instead of the classic process I’ve been using. I also have it working to where all 4 of the tubes will self start a siphon if it is ever lost. All at the cost of added flow in my tank the 167gph could handle both but tubes but is fine for 1.

Appreciate all the feedback. I agree the hob with the appropriate flow rarely if ever loses its siphon. Having the comfort that all of them will restart if it’s lost helps me not have to explain or expect my tank sitter to start a siphon while I’m out. I’m also liking the tube at the top and see how it will benefit me down the road if/when manually starting the siphon.

 

[Dan_P]

I hear you and so have I. It’s an extra layer of protection. I have had air collect at the top of the tube and do on occasion lose siphon in one of the 2 tubes in the overflow (eshopps p1200). Basically I believe it’s due to not enough flow for both tubes (so the air bubbles don’t push all the way out and rise to the top of the utube. I’m a redundancy guy so you won’t convince me to run just one utube. I want to bullet proof the setup ahead of a scheduled vac. CPR makes (or maybe made) a version with an aqualifter to help; that’s what I’m trying to emulate, just want a touch more suction from the Venturi.

When you use two U-tubes, you halve the flow through each one and air bubbles are not easily swept through. They collect. The answer is not two U-tubes for safety but increasing the flow through one to prevent air accumulation. Increase the flow to the display or buy a larger recirculation pump.

 

[DJF]

ok- I have had both tubes in the same overflow working together with only enough flow for 1 tube but both keeping siphon by implementing the Venturi to pull out the trapped air. You may think this is overkill but let me give you this real scenario that happened to me with this exact overflow. I had only 1 tube on the overflow because the 2nd one always lost siphon (due to lack of flow). A sea cucumber got into the overflow and tube the clog caused the tank to overflow. In this design, I have redundant (self priming) tubes handling the flow of 1 tube… myself or a sea creature can pull either tube out removing it from service and the other will pick up the slack. If I increase the flow to a point where both won’t lose siphon, then it is too much for 1 if the other gets clogged.

Other benefits: 1) I visually see if a siphon is broken. (Bubbles in tank) 2) I can easily create siphon manually by connecting hose to top. 3) I can repurpose use of air for micro bubble treatment. 4) added flow in tank