Waterfall Flow & Airlocks in Pipes Explained

In pipework, air or other gases often collects at the high points forming pockets of gas. These pockets of gas restrict the fluid flow, increase the pipeline pressure loss and can lead to increased noise. This is most common with water and air but can occur with any fluid and gas.
These gas blockages in the pipes leads to a phenomena known as waterfall flow. In the video waterfall flow is explained. How to calculate the pressure drop associated with waterfall flow or gas blockages in pipes is also explained.

[@ershadtantry5774]

I used to think that airlocks didn't matter at all, but, now.....!!! Thank You!!

[@34SV]

the bubble wanting to come up; brillant explanation

[@lother4u]

Very useful, this solve my problem, thanks

[@badeconsulting]

At time 13.16 you talk about the bleed valve not suitable in vacume or (siphon loop) lower then atmosphere. How do you remove the air with out letting more in?

[@mcallisterminiatures9649]

how do you calculate the water flow rate needed to pump/blow out an airlock in an open vented system that has a common pool for flow and return, the high point in the loop being above the water surface. 22mm pipe

[@yakyakker]

Thank you. I found this useful for both my professional life and personal hobbies. My aquaponics growbeds now don’t flood and overflow after adding an air bleed hole near the bend. And I have seen the airlock issue flood and damage gravity drained industrial equipment worth hundreds of thousands of dollars, this will help me to avoid it in future.

[@davidsampson1241]

Thanks, how do you determine the size of air valve to use?

[@akbarshaibnuaboobacker8913]

Does this trap air make vibration in riser pipe

[@muldergogo]

Thank you

[@larsaabergstenvik3740]

Thanks for this very informative video! Would it be possible to direct me to some literature on this topic, please?

[@jaffasoft8976]

I'm creating an up-settling system for waste veg oil to filter it for use in a vehicles diesel engine. I have 5 x 44 gallon drums in series. I add 20 ltrs of oil at a time to the first drum which has a funnel that gravity feeds down inside the first drum till about 6 inches from the bottom. The oil then travels up to nearly the top and reaches the outlet then flows out the side of the first drum inside the next drum at the same level down a PVC 1" pipe and again down until 6 inches from the bottom. The lids can come off the drum but i leave them on and sealed, but! It seemed to me that air had a way to travel all the pipes and ways of the system i thought gravity would push it through. But upon first filling the first drum it started to go into the next drum ok but when it reached the 6 inch level of the second drum it stopped and the first drum filled and overflowed. A nice mess went on the floor. I am able to disconnect the hose fittings between each drum, i did that with the first and second drum and it seems to fill the clear hose with oil again and flow. I also sat the lids ajar with a bit of metal so air goes in. I'm not sure if this will work but i put another 20ltrs in and it will slowly gravity feed down in the small holes in the funnel and will see if it will work when i see it again tomorrow. Any suggestions or ideas? Or once the system is primed might it be right? Its more tricky then i thought.

[@fattahrosady7845]

If the diameter of the pipe is 24 inch, is it possible to have an airlock on elbow of vertical pipe by which the fluid is flowing downward?

[@salmanzaheer5060]

Awesome

[@markpdalec]

You blew my mind first sentence my brother and dad's name is Mike crowley.

[@l.crossjr]

If there are no iso valves, how do you intentionally create an air lock when replacing a pump or fixing a leak without draining the system?

[@ritchiemacinnis5680]

Could I experience an air bubble developing in my 1 inch water line which is 1000 feet long and have a 20-foot difference in elevation from one end to the other, it will be buried 4 feet underground in a trench dug by an excavator the bottom of the trench could have irregularities 6 in to a foot (and almost impossible to determine) along the length of the pipe.

[@schatzemanly6749]

Simple answer, yes. Depending on how many and how sharp the turns are you can get air bubbles. Anything other than smooth straight pipe will introduce friction headloss. This will reduce your flow or require more energy for the same flow. Any bends in your pipes will cause headloss; any transitions in pipe diameter will cause headloss. Hope this helps

[@texashog4526]

Can vapor locking be dependent on pipe size and velocity? I’m nervous about installing a high point bleed in hazardous service. It’s only 1.5” pipe at a high flow. Links/evidence would help too!

[@schatzemanly6749]

Vaporlocking is dependent upon many things including pipe size, velocity, temperature, pipe material, fluid being pumped, etc. You don't specify your hazardous service so it is difficult to surmise

[@pointblank1978]

Keep your breathing area upstream from any gas that may come out when bleeding the valve. Or attach a hose and bleed away from yourself. Remember to always put the plug back in the valve when your done

[@aileenm6375]

Thanks Mike, my elderly mum has had several airlocks in hot tap recently. Could this happen if she left the cold tap running for too long? Unfortunately she is quite forgetful. Or might there be other problems we need to outrule before deciding she is causing the problem. Would really appreciate your thoughts as it is really becoming a problem

[@pointblank1978]

For a house, the pipes are small enough to get flow speed to push out any air bubbles. No worries with your mum. Rest easy.

[@zalala]

hmn from ur speech, there should be head loss? but the equation shown that theres head increase due to air locks? did i miss heard u?

[@mba2ceo]

can U do a practical numerical example ?

[@zalala]

sorry to ask again, will there be airlocks on horizontal pipe bend? thanks for the video, very informative, greatly help me on the project im in right now.

[@MikeCrowley]

horizontal bend will not cause airlocks

[@schatzemanly6749]

But any bend will, theoretically, cause headloss

[@SajidAhmed-ko3gz]

Hello.plz tell me abt the releasing of air from penstock pipe of length 3 km.

[@hsharma47]

Sajid Ahmed sir did you get the answer?

[@ragemanoj]

N0

[@davidmaxwaterman]

I guess the 'gas' need not be gas, but any fluid that is of lower density than the fluid being pumped....

[@nasir_118]

The plumber hasn't kept a alternative pipe for outlet of air.so, everytime the tank empties out ,we have this airlock problem.

[@pointblank1978]

On the top of the tank, there should be a pressure gauge. Install short nipple tee and valve. Put the gauge on the tee and valve on the other straight end. Put the valve on and use it to bleed off pressure. If your tank is carbon then air could come in somehow. Haven’t figured out how to prevent it yet. 😁. Hope this works for ya.

[@davidmaxwaterman]

Could a bubble completely block the flow?

[@sergioalejandrocontrerasga1463]

Why H2 is a head loss if there are a fall efect?. Don't we consider that you are gained High?

[@waaades]

I have an application nearly identical to this. The top is vented at the same location as your sketch and releases only water. At what point does the water velocity carry away the air? Is 10ft/sec sufficient? (h2 is 18ft and pipe size is 72inch diameter). Is the head loss "h2" eliminated if there is no air at the vent?

[@texashog4526]

Did your question ever get answered? I’m curious too but I’m not messing with water. Evidence would help

[@waaades]

No - I didn’t get an answer but found the problem. The issue was a vortex forming in a horizontal Tee because the tee was close to a perpendicular elbow in the 72” pipe. We installed a 24” tall wedge in the Tee to direct flow and break any vortex formation. Pressure drop across tee decreased from 6 psi to less than 1 psi.

[@schatzemanly6749]

@@texashog4526 Can I help with a situation. I install air release valves in sewer and water. My friend has his PhD in Hydrodynamics so he understands Bernoulli, Newton and those other guys

[@schatzemanly6749]

@@waaades Wade, I've seen the vortex also in a large pump that had a design flaw. We put in a cross pipe in the suction header and it literally broke up the vortex before it got to the pump. (Warm water with low available NPSH) To answer your earlier question; Yes, the removal of the air will cause h2 to go away because there is no longer air to create a bubble. The water velocity required depends on a lot of variables, but, if you have an automatic air valve installed, that works, then you should never have this issue again. Hope this helps.

[@pointblank1978]

Put a bleeder valve on the high side and periodically bleed off the air. 👍🏽

[@naveenpoonia5425]

So why there is loss in energy I mean when there is no air there is no loss so what's the role of air here , how does it(air) makes energy loss ? Anyone please reply, this doubt is haunting me for a while now ???

[@schatzemanly6749]

The air is a gas. this gas displaces the water. You now have less area to allow the water to go through. This results in more friction - more headloss - more energy for flow. If you had a pump providing the flow and you sped up the pump you would see the pressure gage reading go up (due to headloss) but you may not see the appropriate increase in flow rate (e.g. the water level not going down as fast as expected) This is because the air bubble is acting as a blockage

[@naveenpoonia5425]

@@schatzemanly6749 thanks , that helped

[@ralphmarshall3682]

Bb

[@ishaaqahamed3888]

he looks like Liam Neeson

[@jaedon86]

I would think that he was wrong. The pressure drop in that h2 portion is due to constriction of flow. As area of water flow is constricted by air bubble, the velocity increases and hence pressure decreases (Bernoulli would be a goodstart for rough reference) and hence significant pressure loss. It has nothing to do with h*rho*g effect.

[@piotrturzynski9584]

jaedon86 you are not right mate. He is right but his explanation was not complete. H2 head loss is caused by waterfall. When water goes down (h2 because of gravity force) the level of water changes (drops) and the pump must compensate for this loss to elevate water to the required h1 😉

[@piotrturzynski9584]

Hf i mean 😉

[@elmeracg5831]

Well explained! Agree with jaedon86.

[@timdunk7278]

10:00 head loss

[@BLINK-xl5kn]

Firstly, i would like to suggest to use good mike or just use earphone mike its really hard to hear your voice even with a full volume.

[@thedislikebutton1907]

You should take that advice yourself.

[@debajyotisaha5523]

Be louder