8th circle of hell = Microbubbles cycle!

Here's the ordeal.

I got a HOB overflow box (eshopps), it's a 1" bulkhead in there, and I had it plumbed up with about 6" down from the box out, a 45° elbow, and then 4' of 1" PVC all the way down into the sump.

Here's my theory on what's happening:

Overflow box is primed and running, NO air in U-tube.

Then running to sump, the powerhead is running too high, ends up being partially out of water, which causes it to shoot microbubbles into the tank.

The microbubbles that are now in the tank, are flowing into the overflow box, and gathering up, being sucked into the U-tube, adding up together and forming bigger bubbles, making an air pocket, thereby impeding on the flow.

That in turn causes a crappy flow back into the sump, which slows down the in-flow, causing the powerhead to spit in MORE microbubbles.

Now, that's my theory of what's happening, a cycle of frustration and nonsense. I've reset the flitration many, many, many times. I got so sick of trying to suck the air out the U-tube and ending up with mouthfuls of fish water, so I started taking the U-tube out, submerging it and filling it with water, then I put a bag on , capping both ends, drop it back in place in the overflow box, then pulling the bag till it breaks, releasing the water. That works fiine, and no bubbles, then the following day I got a ton of bubbles.

I've tried setting the stupid powerhead to a slower rate to avoid it letting the water in the return chamber to fall below 6-7" as to avoid it sucking in air, and sure enough it still happens (microbubbles in the tank and air in U-tube).

Is my hypothesis correct? Could it be something else? Like My powerhead being the cause of the microbubbles? Please someone, help me make this stop.

 

any way to raise the water level in the sump so the return pump stays completely submerged? does your sump intake have any kind of bubble diffuser on it, like a filter pad or LR rubble? what is your overflow and return pump rated for flow-wise?

nice idea with the plastic bag trick.

~Will.

 

As far as the flow rate, I honestly don't know. I can't remember what the specs on the box were. But I know I NEVER got that 1" pipe full and blasting out water. Not even with the most direct flow.

Something I forgot to mention. Over the weekend changed the piping on it, fromthe 1" PVC to a 1'2 and added on 1/2" corrogated hosing. I redid the top of the sump as well, i added a lid on the bioball box, that ran LOVELY for about 24 hours and then the bubbles fiasco began again.

I do have a diffuser (trickle tray), whatever you wanna call it. A sheet of plexi and I drilled a bunch of holes with the dremmel. I also left space around the tray, about 1/4" all the way around to allow some faster flow. I also have a layer of White filter floss, and a layer of the typical blue and white filter padding.

I'd hate for the solution would be to take out that padding, it does a lot for me, filter-wise. But I guess it won't kill me.

Any other suggestions?

 

OK, a couple of thoughts:

Reduce the flow of your return pump to it's lowest setting or install a ball valve and throttle it down....at the same time, increase the level in your sump, (but leave room for an increase due to a loss of power or shutting down the return pump)...

If your issue with the u-tube is due to bubbles from the return pump, this should solve your problem...then you can begin to adjust the flow or make other changes as you will be sure of the problem...

 

Yup, turn off the system and raise the sump level to the max on a power shut down. Install a ball valve and hammer back the pump power until you get somethign acceptable. Alternatively you can use a larger sump.

 

The 2 things i see here is 1. the water level is to low in the sump and 2. the return pump is to small for the overflow . with more flow the bubbles would not collect in the u tub they would flush right through.the slower the flow the more chance for bubbles to collect.

 

You can run a smaller pump than the overflow rate. It will only drain what is supplied to it. The main cause of the situation is that the water level in the sump is too low. When the pump sucks air, it will spit it out with the water, just like how skimmer pumps work. The OP needs to bring the water level in the sump up and get the return pump submerged completely. Getting air trapped in the overflow can lead to flooding, a result from a siphon break.

 

I took out the filter padding, and slowed the rate on the return pump. I topped off. the slow is high, but that bubble in the U-tube is a hinderance. I'm not in the mood to deal with taking it out yet. lol

 

there is such a thing as using to small a pump, and after 30 years of using hob over flows and never had a siphon brake from air bubbles not once. i have found the most common reason for trapped air in the u tube is to slow of a flow . im using 3 hob over flows right now and just watch the bubbles flush right through the u tube with out ever slowing down. its much better to use a pump to big and adjust it with a valve to match the overflow rating then it is to use to small a pump with a slow flow.

 

Update from this morning.

I saw a bubble in the U-tube last night. It was gone this morning.

Everything seems to be running fine. Let's see how much of an effect evaporation has.

Wish I could cut back on my evaporation, but it sucks