Siphon Line Air Leak

[Darth_Tater]

Hi all,

I've got a freshwater system running a Herbie style overflow. I'm getting popping noises and air bubbles into the sump through my siphon line. I did not glue this pipe together, so I'm wondering if somebody did that incorrectly, or if I might be getting air leaks from some other component. It looks like this (please ignore the wiring mess from the DIY LEDs):



Both bulkheads and the gate valve have all the O-rings they're supposed to, and all are tightened as far as I can get by hand. The top of the gate valve I tightened with a pair of pliers.

Any suggestions?

 

[Scottedontknow]

did you tape the threads on the gate??

 

[Darth_Tater]

The gate is not threaded, it's glued to the pipe. Or do you mean the threads inside? There's an o-ring on the part that comes off the top, so I figured I didn't need to tape that.

 

[Darth_Tater]

Hmm. The unions have o-rings in them, but should I tape the threads on those too? I don't even know where the leak is coming from.

Any good methods for finding a vacuum leak in plumbing?

 

[bhbell]

My $ .02
1. Don't tape the threads on your unions.
2. Use an eye dropper to drip a bead of water on the tops of the fittings. Do them one at a time and observe both bubble production and if the bead disappears. Kind of like checking a tire tube, but backwards. If bubbles stop or reduce or the water bead is pulled thru the fitting junction the joint is leaking.
3. Soak a paper towel. Roll it up and jam it against the bottom of a fitting joint. Monitor the bubble production. If it decreases, it's leaking.

Sent from my VK815 using Tapatalk

 

[Darth_Tater]

Well, spent a while with a dropper and a couple paper towels and came up with nothing. I'm thinking about taking the whole line and going over the joints with PVC cement or silicone.

It's quite annoying! The noise is coming from somewhere between the bulkhead and the bottom union.

 

[bhbell]

May as well, but if you have fish in the tank..... Is there any chance you're drawing a vortice in the overflow box?

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[Darth_Tater]

Tank is fishless right now, just some plants. They'll be fine for half a day without the main pump.

The bulkheads in this setup are stacked, so the siphon line is a good way down the tank with the emergency line towards the top (the overflow goes all the way to the bottom of the tank). It may be sucking in a small bubble that gets pushed down from the water coming through the overflow, but there's definitely not a vortex. I'm not running this overflow more than probably 1/3 its capability.

 

[bhbell]

Ok. At this point I'd try what you are doing.

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[Darth_Tater]

I pulled the line out yesterday and applied silicone to all the joints that didn't look 100% completely airtight. Whoever glued in that gate valve did a horrible job, it even had salt creep on it from the previous setup.

Even after sealing all the joints it's still making just as much air intake noise. I think I'm going to just get a new gate valve and redo the whole thing. I'll use threaded couplers instead of the unions. I still think the air might be coming from those, but I can't seal them up or I'll never be able to get that line off.

 

[Dross]

If you have a relatively high elevation between valve and the level in the sump and a low flow through the siphon, air is going to collect just below the gate valve. I suspect this is what is causing the noise that you are hearing. Even if your system is perfectly air tight, dissolved air in the water will degas due to the negative pressure below the gate valve and accumualte under it. It does not require an air leak or a vortex. You either need to increase the flow or reduce the size of the siphon to increase the velocity and pressure drop through the line so there is not so much negative pressure below the gate valve. This will keep the siphon line liquid full. The other option is to relocate the gate valve just above or even below the level in the sump.

I am relatively new to this forum, but I have 35 years experience as an engineer dealing with fluid flow. I may be missing something, but I do not understand why it is recommended to place the siphin line valves so high above the sump as this arrangement leads to this problem. The people with basement sumps really suffer from this issue due to the large elevation difference.

 

[Darth_Tater]

Interesting, I actually had a similar thought. However, the noise is coming from ABOVE the valve. It also gets much, much worse as I increase the flow through the line.

I do think though that when (or if, gate valves are hard to find...) I redo the line I will try putting the valve at the bottom. It just makes sense and will still be easy to adjust on this setup. Thanks for the advice!

 

[GauteG]

I agree with the last posts - I have a 40mm/ 1 9/16" siphon, with a ballvalve close to the tank. When the flow is right, I get a quite loud somewhat high pitched noise from the valve. I added a valve at the end of the pipe, in the basement, close to the sump, and now the sound is gone.

 

[miroch]

I thought that 90deg elbows would cause problems? If you are redoing the lines, try 45s instead.

 

[Dross]

Interesting, I actually had a similar thought. However, the noise is coming from ABOVE the valve. It also gets much, much worse as I increase the flow through the line.

I do think though that when (or if, gate valves are hard to find...) I redo the line I will try putting the valve at the bottom. It just makes sense and will still be easy to adjust on this setup. Thanks for the advice!

If there is an elbow pointing down inside the overflow as is typical and the flow rate is very low, the air pocket could be all the way up to the elbow and causing the noise above the valve. You basically just have a submerged overflow.

 

[Lsufan]

Is your 90 & inlet on your bulkhead inside your overflow box submerged? If not then the air could be coming in inside the overflow if it's not glued in the bulkhead. I had that problem once because I don't glue anything inside my overflow & the inlet on my bulkhead wasn't fully submerged. I was really just checking to see if that is where it was coming from so I wrapped a couple wraps of teflon on my 90 & slid it into the bulkhead & it took care of it so I just left it alone & it never gave me a problem again. That was 3 years ago & it is still dead silent today, although I suspect that it worked long enough for a little buildup on the pipe to accumulate to keep the air from getting in.

If it's not that then it could be the gaskets on a union that is letting air in but not letting water out.

U don't mention how much flow u have through the system but if it isn't much flow then that could be the issue too like Dross has already explained

 

[Darth_Tater]

Thanks for all the ideas! I finally did order another gate valve though, so I will just end up replacing the whole line (new bulkheads too) if it ever gets here. UPS is having serious issues in my area right now. I'm going to try to modify things so I can add an elbow inside the overflow and probably even a pipe going most of the way to the bottom of the overflow (the bottom of the two bulkheads is half way up the overflow). I'll try adding 45s too to help avoid any air pockets.

The bulkhead inside the overflow doesn't have anything on it, it's just open. The overflow is too narrow to add an elbow on it the way things are currently set up. It is completely submerged however (water level is at least 2 inches above the top of it with no visible swirling vortex).

The flow is varying. The noise is actually much less at lower flow rates.

Oh, by the way this is a 1" line. The pump is a Jebao (yes, I know... but it was cheap and it's almost silent!) DCT-4000 with head height about 4 feet. I've been running it anywhere from level 2 to level 8, but level 5 seems to give the best flow/popping noise ratio. This pump actually does not give anywhere near the flow I was expecting, so it's good I ordered a size bigger than I thought I needed!

 

[Darth_Tater]

In case anyone was interested, I found the problem. I ended up redoing the siphon line and still had issues and that's what gave me the key clues.

Turns out the water dropping 1.5" from the bottom of the weir to the water level in the overflow was somehow enough to force air bubbles 15"+ clear to the bottom of the overflow (where the new siphon line intake was). These bubbles getting sucked into the siphon line was causing the noise.

I fixed it by changing the non-siphon drain line at the top of the overflow to a 3/4" bulkhead (the rubber gasket barely covers the larger hole for the 1" bulkhead, but it's enough it's water tight so far) and modifying a 3/4" 90 degree elbow (so that it would fit in the very narrow overflow) to raise the water level in the overflow to just below the weir. No more bubbles, no more noise!

Thanks again for all of the suggestions!