HELP! Micro BUBBLES are Driving me Insane!

[Feet4Fish]

COULD USE SOME HELP WITH MICROBUBBLES

So since the beginning of my tank in March I have had a boatload of micro bubbles in the big display and it is driving me nuts. I have attached a video. The come right out of the return line. Interestingly the don’t come out of the return line on my secondary display and that water is crystal clear. RFG nozzles not the sucking air either as I have removed all of them and problem still exists,

Plumbing Description

Let me explain my plumbing set up. Water enter the pump via a 2" line with the water level approximately 14" above the feed bulkhead. Water exits the pump via 1 1/2" pipe. At approximately 40" above the outlet there is a Tee. About 15-20% (valved) of the flow heads out one side to a 90 gallon display through a 1" return line. The other side of the T stays 1 1/2" travels horizontal for 48" then elbows up 10" and elbows and travels horizontal for 25 feet until another elbow to vertical piping up 8' to top of 650 display tank. At the top it enters another Tee that reduces down to two 1" outputs. The outputs terminate into 2 outlets atone end of the tank and two outlets at the far end of the tank. Tank is a peninsula.




Potential causes and actions taken

Split to 2 tanks a problem? No -cut off flow to secondary and no change

Bubbles from sump entering pump intake -Don’t think so as out a sponge/intake screen over pump outflow.

Air getting sucked in plumbing between sump and pump - don’t think so...redid this run twice now for this reason.

is the pump to big? Maybe....it is a Tigershark which is 8500gph with high head. Could switch out the impeller to the hammerhead which will reduce output. - Today switched to Reeflo Manta Ray impeller and which lowered gah to 6500 and no change.


Does anyone else have any other thoughts?

 

[Feet4Fish]

here are some plumbing pictures

 

[Feet4Fish]

Quick thought....could the force of the water colliding with the Tee cause the bubbles?

 

[Tampaman]

Just thoughts, but have you tried turning the skimmer off? My Gyre makes micro bubbles when dirty, that without filter socks, will still go through the drain and return pumps prefilter.
The tank running on the smaller line has none correct?
Maybe those big return lines that have to funnel down to a much smaller diameter in a short amount of time. Turbulent flow at the reduction before the RFGs that needs time or travel to go laminar?

 

[Flippers4pups]

@Feet4Fish,

Possible cavitation at your impeller housing caused by npsh.

I found that reducing any and all angles or any restrictions in my plumbing prior to the inlet of my pump, helped reduce the chances of bubbles forming at the impeller. These restrictions cause a negative pressure before the impeller, allowing air to be pulled from the water causing bubbles to be expelled.

It's possible that the pump is too large or your inlet plumbing has too many elbows or valves. Needs to be as straight as can be all the way to the pump.

 

[Feet4Fish]

Line to the pump from sump is about 18” long 2” plumbing and all straight. Thinking pump might be just too big because info valve it way back on the outlet flow then bubbles pretty much go away. See pic below of how far valved down. What I am trying to figure out is what is the sweet spot in flow and what pump can provide that with about 16’ head?

@Feet4Fish,

Possible cavitation at your impeller housing caused by npsh.

I found that reducing any and all angles or any restrictions in my plumbing prior to the inlet of my pump, helped reduce the chances of bubbles forming at the impeller. These restrictions cause a negative pressure before the impeller, allowing air to be pulled from the water causing bubbles to be expelled.

It's possible that the pump is too large or your inlet plumbing has too many elbows or valves. Needs to be as straight as can be all the way to the pump.

 

[pdxmonkeyboy]

If you want the answer, call reeflo and ask them. This has come up before, it is a function of the velocity entering and existing the pump.

The have mandatory minimums for plumbing leading into the pipes but i cant remember what it was.

 

[Feet4Fish]

I sent Reeflo and email yesterday with same pictures and extensive detail. Hopefully get a response today. I can’t find a phone number anywhere in their website which is unfortunate. Thanks for the advice.

So wouldn’t this be true then for all external magnetic drive pumps or is it somehow just related to Reeflo?

If you want the answer, call reeflo and ask them. This has come up before, it is a function of the velocity entering and existing the pump.

The have mandatory minimums for plumbing leading into the pipes but i cant remember what it was.

 

[Feet4Fish]

Ok. So I read this..... I think the problem is likely the fact that I have a Tee only 30” from the pump outflow. My problem is my basement has really low ceiling and is super small and not under the room with the tank. The most I could raise the Tee is about another 8”. This would bring the height to 38” between the pump outflow and the Tee.

does any one have any idea if that replumbing would even be worth it or would it likely result in the same problem?

 

[Feet4Fish]

Bump

 

[pdxmonkeyboy]

They should respond to your email. It is not a function of the reeflo pump, it is a function of the very high flow rates and pressures. Plumbing Ts are ridiculously ineffecient at high flow velocities. This turbulant flow is causing an area of low pressure, which pulls air out of solution. You know how a matis shrimp causes a clicking sound because his arm moves so fast it causes a cavitation and air bubble.. same thing here.

I would try to raise the T if you can but also replace the T with a DWV (drain waste vent) long sweep sanitary wye. They make them out of pvc these days. They are not pressure rated but an aquarium is nowhere near their failure pressure. This design will flow more smoothly thus causes less pressure differential and cavitation.

 

[Feet4Fish]

That is a wonderful suggestion. I am contemplating removing the entire Tee construct and running the small tank of an independent pump. Then I can replace the Tee ..... would a sweeping type elbow be better or 2 45s?

They should respond to your email. It is not a function of the reeflo pump, it is a function of the very high flow rates and pressures. Plumbing Ts are ridiculously ineffecient at high flow velocities. This turbulant flow is causing an area of low pressure, which pulls air out of solution. You know how a matis shrimp causes a clicking sound because his arm moves so fast it causes a cavitation and air bubble.. same thing here.

I would try to raise the T if you can but also replace the T with a DWV (drain waste vent) long sweep sanitary wye. They make them out of pvc these days. They are not pressure rated but an aquarium is nowhere near their failure pressure. This design will flow more smoothly thus causes less pressure differential and cavitation.

 

[Feet4Fish]

How about this?

 

[pdxmonkeyboy]

If you are taking the T out of the system then a regular 90 would likely suffice. That picture or two 45 would work as well. Some people start building all kind of multiple 45 turns to reduce pressure loss, but in our applications, the loss from 90 turns is pretty much discountable. The real problem is all the turbulence that a standard T induces in a system.

If you don't want to use a separate pump, I would think the WYE I posted would solve the cavitation problem.

 

[DCR]

The 2" suction line is just too small for the amount of water flowing through it and the liquid head you have above the pump. You are getting negative pressure at the inlet to the pump and it is causing dissolved air to degas from the water. You need to either reduce the total flow by throttling the discharge to reduce the head loss in the suction line or significantly increase the liquid height above the pump to increase the pressure at the suction. You would probably need several feet so this is not likely to be practical, but it would be the best solution if you could lift the sump up above the pump. It is highly unlikely that it is anything on the discharge since the pressure is higher at that point and there should not be any degassing.

I have done industrial pump installations as a career and realistically you probably cannot flow get more than about 3000-3500 gph through a 2" suction line without getting into problems like this. This correlates with about 4.5-5.5 feet per second. I would normally size most suction lines to keep the velocity down to 2-5 ft per second. Even then I would want a lot more than 14" of liquid above the suction nozzle.

 

[Feet4Fish]

So if I was to raise the sump which is feasible that would then require a 90 to drop to the pump. Would that cause any issue? The folks at Reeflo advised me to create a straight shot from sump to pump inlet. And if I did raise the sump would it be of any benefit to increase the diameter of the piping between the sump and the pump intake? Thanks for your help!

The 2" suction line is just too small for the amount of water flowing through it and the liquid head you have above the pump. You are getting negative pressure at the inlet to the pump and it is causing dissolved air to degas from the water. You need to either reduce the total flow by throttling the discharge to reduce the head loss in the suction line or significantly increase the liquid height above the pump to increase the pressure at the suction. You would probably need several feet so this is not likely to be practical, but it would be the best solution if you could lift the sump up above the pump. It is highly unlikely that it is anything on the discharge since the pressure is higher at that point and there should not be any degassing.

I have done industrial pump installations as a career and realistically you probably cannot flow get more than about 3000-3500 gph through a 2" suction line without getting into problems like this. This correlates with about 4.5-5.5 feet per second. I would normally size most suction lines to keep the velocity down to 2-5 ft per second. Even then I would want a lot more than 14" of liquid above the suction nozzle.

 

[Feet4Fish]

Thanks so much for your help. Will he the fittings I need and make this adjustment tomorrow or Friday. Will definitely report back!

If you are taking the T out of the system then a regular 90 would likely suffice. That picture or two 45 would work as well. Some people start building all kind of multiple 45 turns to reduce pressure loss, but in our applications, the loss from 90 turns is pretty much discountable. The real problem is all the turbulence that a standard T induces in a system.

If you don't want to use a separate pump, I would think the WYE I posted would solve the cavitation problem.

 

[DCR]

So if I was to raise the sump which is feasible that would then require a 90 to drop to the pump. Would that cause any issue? The folks at Reeflo advised me to create a straight shot from sump to pump inlet. And if I did raise the sump would it be of any benefit to increase the diameter of the piping between the sump and the pump intake? Thanks for your help!

Yes, if you could raise the sump 2-3 feet (the more the better) and increase the line size to 3" with a reducer right after the last elbow and then about 15-18" of straight 2" into the pump suction, I think it would give you much better performance. You might still need to throttle the pump discharge back to stop the bubbles, but it would not be nearly as much flow reduction. I do agree with Reeflo that you want at least 5 pipe diameters of straight run equal to the pump inlet size. This is to minimize the turbulence entering the pump. Once you go to 3", the additional elbows will not matter that much. With the 2" the additional elbows would cancel much of the benefits or the higher liquid height. You might also need a vortex breaker on the sump outlet connection but this can be easily fabricated and installed afterward if it becomes an issue.

That is quite a large system for a home aquarium.

 

[pdxmonkeyboy]

@DCR .. what is a vortex breaker?

 

[pdxmonkeyboy]

Nevermind. Googled it. Neat.