Backyard Aquaponics
A place to discuss aquaponics

Simple water bridge. Used a pump to flood the bridge from bucket to pipe but the water does not equalize, pipe side water level stays low and the bucket level high. What am I doing wrong? The goal is to have both sides equalize at the same height.

In the red bucket, is the PVC sitting flat on the bottom. Try lifting it a little so the water can move. If not there may be an air pocket or if you pump is connected to the other end it may not allow the water to move back through the impeller quickly.

You either have an 'air lock' in the overhead pipe, i.e. the pipe is not completely full of water, or because the ends of the pipe are touching the bottom of the bucket (and possibly the pipe base?) there is no way for water to flow in or out to equalise.
Try lifting the pipe bridge so that the bottom openings are at least the diameter of the pipe from the base of the two containers. Atmospheric pressure will then be able to equalise the water height in both containers.
You need to ensure that there is not any air in the pipe, a pumped flow may have not filled it completely. The only way to ensure the pipe is full of water is to have a definite high point and fit a small air bleed valve at this high point to expel all air in the system. This can be a simple needle valve that you manually operate until until only a stream of water comes out of it and then turn it off.

Just noticed Duff's reply, same thoughts here!

Cheers Ian K

I added a couple 90s to the bottoms of each container but I guess I still have the 'air lock' which is preventing the water to equalize.



I'm going to have to read more because I'm not sure how to do that with PVC but I have a feeling it's on this forum somewhere.

Thanks for the quick response... back to the drawing board.

Try this. .
In our cotton farming areas in the west of new south wales, they 'dip' fill black poly pipes in the water supply canal until full, put their hand over one end, and drag it over and into the irrigation channel. This acts as a siphon to try and achieve "balanced" water levels ( after all, that's what a siphon does).
For normal town water supply reticulation, which goes up and down hill, you will find 'automatic' air bleed valves at high spots to eliminate the air locks that will stop this siphoning action.

Hope this helps.
Cheers IanK

Thanks Ian! I gave it one more try while the sun was still up. Failed, but I'll give it another go tomorrow. Does it require a needle valve or will a regular ball valve work?

OK, Goola, I'm not going give up just yet!!
Let's try lifting the TEE and Valve up, just bend the PVC pipe bridge, it won't hurt it, and expelling all the air at the very top. I don't think that a ball valve would make much difference, just that a needle valve has much finer control to let the last little bits out.

To prove to yourself that a pipe bridge does work, try the following:

Use your current Bucket and pipe sitting on the deck. Fill the bucket with water but leave the pipe empty.

Use a piece of hose to create and maintain a siphon from bucket to pipe.

When all settled, pour water into the the top of the pipe and the Bucket will eventually overflow!

Now you know it works, just fiddle to get rid of the air in your PVC bridge to make it work. It will continue to work until air eners the system, either from the pipe ends.. . . . or unsealed fittings! that allow just enough air in to halt the system! Are your elbows and Tees etc pressure tested?

Cheers IanK

Nice explanation of how to do a basic drain siphon, Ian! Cover's off all I would recommend.

Goola,
Try doing what Ian suggested with a clear hose, so you can see the air pockets that will form.
Then when you have it working, get a pin and prick the hose to show what effect even the tiniest leak might have.
It is possible yours wont work if the elbows are not glued, as sometimes air can be sucked in through the joins.


General Principal.
Fill the water bridge.
Add water to one bucket, this will increase the pressure at the bottom of the pipe, making it larger than the pressure in the other bucket, so water will rise up the pipe, and out the other end.

However, if you have an 'air lock' ie a "solid" pocket of air with no water, then it wont work.
The pressure will increase in the first bucket, and water will travel up the bridge, but air, as it is easily able to be compressed, will choose to compress rather than move the water out the other end.

if you have a partial air lock, and water can flow below it, your flow rate will be DRASTICALLY hampered, however the bridge will still work.

Due to water having gasses dissolved in it, and sometimes 'off gassing' these gasses as pressures and temperatures change, then over time your water bridge will get air in it and lock up. It is therefore generally advised, that in the highest point of your bridge, that a clear bit of pipe is used, so you can see the air lock forming, and suck it out with the valve on the top that you've already added.

I admit it. I didn't glue everything together, so that is probably why things aren't working.

I'm starting to question the stability of the water bridge though. As such, maybe you all can help me improve this design. I am trying to expand my indoor system to support two dwarf trees (lemon & clementine). My thought was to bridge the water from the fishies to a standpipe, then ebb/flow pump the water from a reservoir underneath the citrus trees to the growbeds on top, which drain into the fish tank, which would raise the water level, causing the water to flow back over to the trees, then back in the reservoir.

This is in my house so the last thing I want is an air bubble in the middle of the night flooding my living room. How can I make this flood proof?

A water bridge or no holes overflow has that major drawback, it can get gas and fail.

If you can put a hole for an overflow a bit below (low enough so that growbeds draining won't overflow over the top of the tank) the normal high water level in the fish tank, then you can install a SLO to feed over to the addition so then your system could operate like a CHIFT PIST system with your original grow beds acting like extra grow beds over the fish tank.
Would something like this be acceptable?

The problem is that I don't want to drill a hole in the fish tank.

I do understand now wanting to drill a hole in the fish tank. Problem is, even when you get a good water bridge going, you still have the risk of airlock. Now there are aquarium over the side overflow set ups that are probably a fair bit more reliable than a PVC type water bridge but they all require regular checking.

Hi.

My local fish store, the Aquatic Critter, sells a clear U-shaped 1 inch pipe used for these type of overflows. Clear is nice because you can see if it is developing an air lock.

Related: If you are really worried about a flood, there is a $10 mini water/vacumn pump called an aqualifter. Big aquarium geeks use these to insure their overflows stay primed. You plumb a line from the highest point of the waterbridge to the lifter, and a waste line from the lift back to the sump. It constantly sucks a little bit of air or water out to keep it going.

http://www.bigalsonline.com/StoreCatalog/ctl3684/cp48948/si1380205/cl1/tom_aqualifter_pump?&query=lift&queryType=0&offset=0

That's $10 US. Shipping to down under would probably make it $50. I feel sorry for you guys sometimes.

-ellie

Thank you! Ordering it right now!

Thanks to everyone that helped me with suggestions. I ordered an aqualifter to make sure the bridge stays primed but in the meantime I decided to use the KISS method and use a simple poly tube to run the water bridge so far. As of now it's working well, but I do worry that the water flow isn't going to be enough. Anyway, at least the Lemon and Clementine trees are in their respective spots.

Trees:


Water bridge: