Overflow stopped working

[consumer]

Hi there, I know there are a million overflow problem posts but this one is slightly (maybe) unique. I have an overflow like this one:

Except, the air tube is on the cap "L" and not on "F" as in the pic.

Anyway, I have two of them. The first one runs as a siphon that is adjusted to run slightly less than the output of the pump from the sump (adjusted through a ball valve at "N"). The second one runs as an overflow/trickle filter that catches the remaining water and as a backup. The whole thing runs completely silent and has been working fine for as long as I've had it (about a month or so).

I have the air tube in the water. When the power goes out, it continues to drain, and then when the water level gets below the air tube, air gets in to the air tube turning it into an overflow/trickle. This is so that when power comes on, the output pump puts water in the tank and then water rises above the air tube and turns it back in to a siphon.

Anyway last night I tested it (turned pump off so the overflow continues to drain). The problem is that it's not turning in to a trickle when the water level gets below the air tube unless I turn the ball valve all the way to on (no flow restriction). But that's no good to me because the siphon will run faster than what the return pump will output, so I need it to run a bit less than.

The thing is, it used to work (I'm 99.9% sure it did anyway). TL;DR - It just doesn't have enough sucking power to suck air in that little air tube unless the siphon runs at full (or almost full) strength.

Any ideas?

 

[Rybren]

I have a couple of thoughts:

- this type of overflow is notoriously unreliable - especially on startup after a power failure, etc.; users usually end up with a wet floor (ask me how I know )

- To act as a siphon break, I think that the hose has to be in elbow E or F. Having it in the cap at L does nothing for you as that area has no flow through it and is almost always full of trapped air anyway.

- Some people have managed to lessen the risk of a flood by having the hose at E or F attached to an aqualifter. This way, on startup, the aqualifter will suck the air out of the top of the inverted U and will help get the oveflow going again. This method is not foolproof.

I think that your best bet is to either buy a quality HOB overflow of better yet, drill the tank.

Just my $0.02

 

[sde1500]

That's a weird overflow. I can't say I understand the problem really, but a month in and having issues is not good. I've run my HOB overflow a year now with little problem. It's not silent, but it's very quiet and restarts every time. Only needs the occasional u-tube cleaning. Might be something to look into.

 

[bhbell]

The air suction line needs to be moved to E F. Its sole function is to pull air from E F to restore the siphon that makes this work. I agree completely with Rybren. This will be far too much trouble to keep working.

Sent from my VK815 using Tapatalk

 

[Sandy Cheeks]

You are better off with a HOB unit and better yet, drill for an overflow if you don't have anything inside and you are just testing the system.

 

[ca1ore]

Right, as long as E/F are above the water surface, drains will not restart without some kind of air evacuation from the airline. Approach is very 1990.

 

[consumer]

Ok thanks everyone. I did initially have it at E/F to begin with but changed it, I can't remember the reason why. Anyway I had tested it on a smaller setup for over a month with my current setup and it was fine.

I would love to drill it but it's already set up unfortunately. I will create another pipe with air tube in E/F and look in to an aqualifter.

 

[reefteaser]

I used to run this kind of setup before my current tank. The pvc was much slimmer than an overflow box, which is why I used it, and it was fairly reliable. I did have several issues with it when initially setting it up:
The "height" of the H/I section relative to the rest made quite a difference on its ability to self start after a power outage. This took some trial and error to get right.
The tube on E/F was only there to create the siphon, thereafter it was not used unless I pulled the thing to clean it.
I had another air line with a small small valve at L to fine tune the flow, and no valve at all as depicted at N. This, combined with the proper combination of pipe diameter and return pump flow made it possible to maintain a fairly steady water height to A, and make it almost silent.
It worked pretty well, but if I stuck my arm in the tank to move a rock, clean, etc., and removed it quickly the rapid changes in water height could disrupt the siphon. Also, if something should get into the pipe, without a safety drain the risk of an overflow is high.
There might have been other issues, but it's been a while. All in all, my current setup using the herbie method on a drilled tank is far and away much better.

 

[reefteaser]

On more thing, if the ABCD section is itself in an internal overflow box ("weir"), than small fluctuations inside that box would not effect the water height in the rest of the tank, and help keep debris from the drain.

 

[consumer]

Yeah actually it was quite reliable with my testings. Also I realise that the picture I linked is not exactly how mine is set up. Remove section A, B and C. Like you mentioned reefteaser, mine also sits in a mini wir outer pipe that catches debris.

Also my D is the same height as G. Looking at that picture I linked, it is a bit different than mine but similar.

Anyway I remember why I had the air tube at the cap ("L") now; This overflow design is just that - an overflow. I got it off the King of DIY on youtube. He said that the air tube is important because it's what turns it in to an overflow and not a siphon.

My design (design? I guess you could call it that) I push this air line in to the water so I get a siphon (can handle more water, is quiet, etc.) and so first the overflow/trickle starts, then when the water level gets high enough, a siphon is produced. Once the trickle starts, the siphon works always. But my problem is that the trickle doesn't start unless I turn the ball valve all the way on. If I slow down the flow a bit, then the trickle won't start. Well, it does, but it just just drips in very slowly.

So yeah it's not the siphon that's the problem here, it's getting the trickle thing to start. The siphon takes care of itself once the trickle happens. Sorry for my poor explanation, it's a bit hard to explain. I just know that the trickle isn't starting because there isn't enough suction being created in the air tube unless ball valve is fully on. Maybe my air tube has a small blockage that only shows problems when minimal flow is desired, I don't know.

 

[reefteaser]

If your B/C is the same level as H/I, this may be your problem. Try dropping It lower, while making J/M a little higher than B/C.
I think this is how I made it work, but again it's been a little while. I distinctly remember having to tweak the design a few times to get it to work. You might also try using the valve at N on the return pump to get the right amount of flow relative to your pipe diameter, and not restricting the overflow output.

 

[consumer]

Yeah maybe H/I has to be lower than B/C. But the design I followed definitely wasn't like that and the guy whose design it was seems to be fairly knowledgeable in that area. But yeah maybe it will help.

 

[7thdarkangel]

For more reliability "j" need to be above "b&c".if you draw a line straight across from "j", that's where the level in "a" is going to want to be with no water to feed it. I ran one similar to this for a year and a half before changing tanks with no issues. Restarted every time after the pump was shut off.

 

[consumer]

Ah ok, I do actually have my J above the B/C part. Must be the air hose or something. It seems a bit dirty at the end so might try chopping that part off. Am away from a few days so will see when I get back.

 

[BlueRoofTang]

Without a way to get air out at E-F, you will always have problems with it. Small air bubbles will accumulate there. It may be a day, a week, a month, or whatever...but it will slowly reduce flow and you will have a flood.

It doesn't matter if E-F are above or below tank water level..they will trap air. The only difference it will make is that if it's below tank level, your "vent" tube will have to be above tank level or it will leak out water.