DIY Overflow Pipe

Has anyone ever tried this? This user on Ultimate Reef (donkey) is pretty creative. He also makes nice videos. This one took me a while to understand but it's sort of brilliant.

http://www.ultimatereef.net/forums/showthread.php?367635-DIY-OverFlow-Pipe



Took me a bit to figure it out, but I've got it now...what he calls the "anti-siphon valve" is what I call a check valve. You prime the pipe, suck the air out, and then the pipe always stays full as long as you don't get a bunch of air getting sucked into the overflow tube, which if designed right, shouldn't happen.

I had to watch parts of the long video to figure out how to keep the clear overflow tube from floating, which isn't obvious from the diagram above. What he does is make this tube so that it matches the inside dimension from the bottom of the tank to the underside of the trim, then he wedges that pipe in, using the trim to keep it in place so that it doesn't float out of the water when you shut off the pump flow and the water drains out of the weir tube. Then he recommends pushing a rock up against it. So you have to be able to do this (keep it in place)

Then, he uses a valve on the outflow (from the pipe to the sump) to essentially tune the drain to match the return pump output so that the weir tube doesn't run faster than the pump. If it does, I think the water level in the weir tube would go down until the breather tub breaks the siphon and lets air into the drain (to the sump) and then the weir tube in the tank fills back up, purges the air out, cycle repeats.

The catch with this design is that you have to position the return pump so that if that if something goes arwy (something causes the overflow to stop while pump is still running), it doesn't cause the tank to overflow. This takes some calculations and testing to make sure you did it right. Essentially you would have to make sure that in this scenario, the return pump would start sucking air before it overflowed the tank. It's a pretty simple volume calculation.

The danger with this system is the tank overflow concern. I look at the worst case scenario. Let's say you have an auto-top-off system. Let's say that it's in a 5 gallon bucket. Let's say that you just filled that bucket up. Now let's say that the ATO pump sticks in the "on" position and empties the bucket into your system. Now, your pump is too far under water, because that ATO bucket raises the water level in your sump - your tank level is defined by the weir tube, so that will never change. Now, lets say you have an overflow tube failure. Your pump in your sump will keep pumping water until it sucks air. This would push the additional 5 gallons above and beyond what you had calculated for up into your tank, potentially overflowing it.

The solution is:

1) keep your ATO reservoir to the size that prevents the above scenario from being able to occur
2) Manually top off your sump and be vigilant not to overfill
3) have a max-water-level alarm in your DT that cuts out your return pump when it is reached

Something along those lines. Maybe that was addressed in that thread but I haven't had time to read it.

It actually makes me want to try this in my tank (sumpless non-drilled 120)

Where this idea really shines is in smaller tanks, or maybe in an existing larger sumpless tank where you want to be able to put in a small sump with a low turnover rate for some reactors or something. After listening to Bob Fenner at SF and hearing his opinion that low-turnover sumps were perfectly fine, this could apply to a lot of builds.

I suppose you could even build a tank to utilize this. Or, use an existing RR tank and seal off the holes (like, if you had a stand that didn't jive with the location of the holes)

 

How could fish get past the teeth on the weir pipe? Jump over?

In the "take 2" vid he shows that he bonds the check valve, I would think you could just use a threaded fitting and then once it's used initially you just put a cap on it or a piece of airline hose and clamp it to keep air from getting in even if it does fail.