Fix my squeaky water!

December 30, 2009 3:00 PM

I have a tub of water draining into a small hose - it's creating a horrible squeaking, help me fix it!

I have an immersion circulator which pumps water into a small plastic bin. It drains through gravity when the water level gets high enough.

Problem is, I get a loud squeaking sound when the water level is at a certain height (which happens to be the equilibrium) and a vortex is created from the surface of the water.

Video is here (youtube). Might have to turn it up to hear the squeaking (taken with my phone). In actuality it's really loud, I can hear it from a room away even with the door closed.

Any ideas on how to fix this?

posted by wongcorgi to science & nature (9 answers total)

The thing that is making the squeaking noise is probably air bubbles that are either getting sucked into the drain tube and possibly expanding from the heat of the water. So, if the open end of the barbed hose connector is threaded you might want to attach a 45º elbow onto it, facing upwards. This will raise the water level somewhat, but more importantly could get rid of some of the air that is being sucked into the drain hose. In my imagining of it the air bubbles would be forced up and away from, rather than across and into the drain tube.
posted by kuujjuarapik at 3:21 PM on December 30, 2009

I can't tell what's going on from the video well enough. Can you describe the system a bit more? Where does the water come from, where is the pump located (pumps from where to where), where does the water go, that kind of thing.

My impression from the video is that the hose is the pump suction, trying to draw water from the surface of the tank. Sucking from the surface is pretty much guaranteed to make an annoying noise. That scenario doesn't quite sound like what you're describing, though.
posted by ctmf at 4:01 PM on December 30, 2009

Water is being pumped into the bin from the circulator (located below the bin) on the opposite side. What you see in the video is the tube that drains water back down to the circulator. When the water drains, the outlet isn't complete submerged and it is picking up some air and that is creating the noise.

I will definitely try kuujjuarapik's suggestion and pick up a 45 degree elbow.
posted by wongcorgi at 4:23 PM on December 30, 2009

Ok, I'm not 100% clear on what is going on, but is there a reason why the flow of water back into the circulator needs to be limited? Like, for instance, could you have the outlet of the bin be at the bottom and have the circulator itself provide the limit of the intake?

Another possibility might be that it's not the air going into the hose from the bin which is a problem, but perhaps there's a small gap/hole in the threading or whatever connection between the hose and the bin and that the noise you're hearing is from that.

You might also want to just get a bigger hose and bore out a larger opening and see if that fixes things, if the problem is due to some kind of airflow restriction.
posted by cali59 at 5:00 PM on December 30, 2009

I like the elbow idea, but I would point it down, not up, so that the opening is always submerged. This would keep air from being sucked into the drain.
posted by Old Geezer at 5:27 PM on December 30, 2009

The circulator doesn't limit incoming flow. The issue is definitely the air being sucked in. Here's a better shot of the vortex that's causing the noise. If block the outlet and let the water rise higher, it's completely silent.
posted by wongcorgi at 6:15 PM on December 30, 2009

Oh. I thought it was just a gravity fed drain hose. If there is suction on it, the elbow would probably work better facing down.

Another thing to consider is changing the equilibrium point by adding some solid mass to the circulating tank. Like a small brick or something that would raise the water level just a little bit more, and disrupt that little vortex you've got going on there.
posted by kuujjuarapik at 8:09 PM on December 30, 2009

If the water level needs to be where it is, put a little length of hose on the inside of the tank drooping down below the water line. The pump suction needs to be submerged. Ideally, for best circulation, you'd have the suction at the bottom, and the fill line at the top. All the water that's pumped out is pumped back in, right? So the overall water level won't change. You may need to make up for evaporation once in a while, say daily.

If the tank level doesn't matter, just add more water to the system until the water level is farther above the suction line.
posted by ctmf at 9:58 PM on December 30, 2009

This is a common problem with large fishtanks featuring overflow mechanisms. There are many solutions, but I recommend checking out the plumbing section at reefcentral.com. You will be able to find out what you need to do to muffle the sound, probably through some variation of a weir or durso standpipe. You can miniaturize those plumbing constructions with much smaller fittings to achieve the same results. You basically want to create an s trap (or whatever it is called) and siphon out the air (can be done by forcing water through to get it started). The overflow will still function the same way (can be self-starting), and you can still have the water level at the same place (or wherever you want it) after some initial adjustment.

Check out the google image results for "reef overflow" and you can see physically how they work. Like I said before, I think your best bet is to miniaturize one of those mechanisms just by using smaller plumbing fittings.

Its like a toilet - if you add water, the water flows through the s trap (or j trap) or whatever, and flows out the bottom. Water level stays the same. If the output of your overflow is under water, it will be pretty quiet.
posted by kenbennedy at 11:15 AM on January 4, 2010 [1 favorite]