Backyard Aquaponics
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Yep this thread is full of notes about how the no-holes overflows and water bridges require re-priming or removal of the air bubbles that can lock it and stop them from working. There are several methods listed in this thread for dealing with these problems but they all need to be checked regularly to make sure they are still flowing.

Does your NoHoleOverflow restarts itself after power interruption?

If it has remained primed, and no air bubbles have gotten in, then yes, it will continue after a power outage.

The one I have posted in here somewhere with the small siphon tube in it works great. If the power is out for a couple of hours, the tank level will eventually go down a couple of inches and break the siphon.

It's critical to make sure you prime the siphon again when you get power or you'll have a huge mess.

Mine has U bends on the ends, so the water never drains out and thus is 'self-priming.'



Full sized pic here.

Hi All,

I've been giving this issue some thought recently. The inverted U bridge tank overflow's weakness is losing prime.

I haven't seen any mention of this but, if it has already been discussed, apologies. What if we prime it with our tank inflow. I have seen aeration venturis mentioned on this forum. This concept is generally know as a 'jet pump'. In aircraft fuel systems they are commonly used to distribute/ equalize fuel in a number of tanks using one pump. I'm sure you can see where I'm heading with this.

My thinking so far is that we could have our tank (GB or FT, or whatever level we are trying to limit) inlet at the maximum level- ie high tide level. The inflow is essentially a jet pump to our bridge overflow. Something like a T, or + fitting. So in normal operation it would just flow into the air, ie our unfilled GB. But when the water level reaches the level of our jet pump, the 'backpressure' of water in our jet pump would prime our overflow U tube.

The level of this overflow jet pump, I would imagine should normally be slightly higher than the normal high level of our GB, ie higher than our normal siphon start level. So under normal conditions it would not operate. However, say for example, when our siphon didn't function or our regular drain was blocked etc the jet pump overflow would kick in.

The potential problems/ limitations I can imagine are-
1. a sufficient flow velocity into the GB is required, so a sufficient pump pressure is required,
2. the flow velocity can be increased by using a smaller outlet, but this will increase restriction, power requirement etc. This also makes a blockage more of a possibility.

Perhaps having a T'd/ dual tank inlet with one branch a normal open outlet and the other a jet pump overflow. More complexity and expense perhaps? Maybe still better than the options?

Depending on the head height of the overflow U tube, ie 'freeboard' height of the tank would determine the flow required through the jet pump to prime the overflow. Generally quite a small flow should be sufficient.

Just thoughts, I'm sure there are people here with far more practical experience here.

Comments suggestions please.

Cheers All.

Can you draw me a picture?

Would this type of design (which would have a single hole at the top of a tank, I admit), which ads an 'emergency' overflow channel re-prime the system if it was ever engaged?

If it's not clear, basically it has an overflow pipe that feeds into the top of the 'T', so that if the siphon breaks, and water rises too high, the overflow kicks in to save my floors...(indoor setup)....thoughts? feedback? warnings of doom?



edit: hmm...sorry about the oversized image, not sure why it's not resizing...and even more sorry about the misspelling in venturi ... :/ pleading exhaustion

To the best of my knowledge, there is no way to automatically restart a no-holes overflow. The most common problem I have had is tiny bubbles building up in the highest point so that, over a period of days or weeks, the water level slowly rises and overflows. I usually have a standpipe, transparent if possible, at the highest point to allow more air to build up before creating trouble. I also have a valve so I can suck any air out when I see it building up.

i had 2 no-hole-overflows when i was using 3 55gallon glass tanks, used 1.5" pvc.. after fiiguring them out, and making them stable on the tanks, they were fine for 6 months.. they probably would have been ok for longer, but i changed my system

Thank you both for the feedback...

Keith - I don't suppose you have any pics of the old setup? It seems some have zero problems once they're 'locked in place' and setup - while others say they're hopeless...quite the mixed messages

about 2/3rds of the way down the page
viewtopic.php?f=18&t=8354

Thank you!

What do you think happened to require the reset of these?

once, i had an airstone to close to the inlet, and got air in one of the pipes,, it just slowed it down but didn't stop it.. fish knocked them around a couple times.. after i secured everything they were fine for quite some time, but i always had that worry in the back of my head..

Gotcha.

Do you think that 'emergency overflow' drain I added and connected at the top of the T would re-prime it/get it going again if worse came to worse?