I also did not want to drill my tanks, so I made an overflow based on Joey's (updated) model. He has an older version and a newer, I went with the newer. I have four, 20 gallon tanks all hooked into the same sump using the same overflow design. The PVC components are 1/2'' and the inflow/outflow in-tank PVC chamber (or, weir) is 3'' PVC. It works well, but only after a lot of trial and error. Avoid my mistakes:
1. DO NOT drill a hole in the weir for a suction cup, or for any other reason, even though Joey does it. Without going into detail, trust me that a) a suction cup doesn't even work to keep it in place if the water level inside gets lower than the water level in the tank, and b) any water entering that hole is serious trouble in the case of a power outage. To keep the weir in place, lodge another, smaller piece of PVC (3/4'' or 1'' works fine) between it and the top rim of the aquarium, maybe attaching it with a rubber band to the outgoing overflow PVC. This has worked very well for me. Make sure there is enough space so that the water level is always visible from outside the tank. This is important because if the system isn't working, you will need a few seconds to get everything turned off. If the water level is above the black aquarium rim, you won't have any warning that there's trouble until your aquarium overflows over the sides.
2. Seal the connection between the PVC cap and weir with your aquarium sealant of choice. I can't emphasize enough that the weir compartment should be waterproof. You only want water overflowing into it and not being able to get in any other way.
3. Joey claims that with the Tom's Aqua-lifter, the system is foolproof in the case of a power failure. I have found this to be true, as long as the PVC outflow is 1/2'' or larger, the in-tank PVC compartment has a large diameter and there is a significant drop from the tank into the sump. I have another tank hooked up using 1/2'' PVC with a small drop, and I have to prime it every time I turn it back on because the Aqua-lifter needs help. After a long break between uses, I would highly recommend priming the system, no matter what.
4. I would highly recommend gluing all the PVC components together, if a few components come apart the system will dump the excess contents of the sump on the floor, and your water pump will run dry. If you don't use glue, and I don't know why you wouldn't glue for a 125 that presumably will be in operation for a long time, make sure you have quick and open access to the back of the tank where the overflow runs to the sump.
5. I put an airstone with a high rate of air right next to the inflow/outflow PVC, which helps the water overflow into the weir. It also provides good aeration that was lost when I took out the sponge filters (I don't need them with all the bio-filtration in the sump).
6. The aqua-lifter tubing does need to be replaced every few weeks, especially if it's near a strong light source.
That's all I can think of right now. Like I said , I've been using it for months very successfully (after the trial & error period). Be prepared to stay close to the system the first few times you use it to ensure you don't find more design bugs. When it works, it's great. When it goes bad, it's really bad. Drilling would be a much safer long-term option.
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PVC diy Hang on Back Overflow
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Originally Posted by rickztahone
