DIY overflow and sump question

The wife talked me into setting up my 75 gal tank again and this time im going with a diy sump. Unfortunately my tank is not drilled so we will be building our own overflow and i was wondering why it is common practice to use an overflow box instead of just plumbing in a siphon tube. The only reason i could see is for livestock safety. Is it sucking hard enough to hurt fish or is there something im missing? thanks for any advice, these forums have saved me and my fish more times then i care to count!

 

If the tank is empty try to drill it. A million headaches averted.

 

I agree with drilling your tank. There is too much to go wrong with an overflow. When i started I setup a 100g with an overflow and at 1 in the am I had a feeling something was wrong, I got up and it had lost suction and started overflowing. At least I caught it just after it started but I always had trouble with it keeping siphon. Especially if your not home and the power goes out. You can get good drill bits for $15 at gl*******s.com. To answere your question though is that if you just have a siphon hose and no box if your pump goes out or electic goes off it will keep siphoning untill it gets to the end of the hose which could overflow your sump. The overflow box in theory holds water on both sides so that if you lose power it is supposed to hold water in the u tubes so when the power comes back on it will resume siphone. In my experience and im sure others is that it is the u tubes build up air inside and start to lose suction.

 

I personally have a eshopps pf800 overflow box on my tank. I can shut the power off in my tank for an hour and it will not loose the suction. Just prime it the right way with no air bubbles in it

If you have the option, I would drill it. Unless you don't feel comfortable doing it

 

I have en eShopps PF-300 overflow and it has never lost siphon (more than three years). Even after losing power for more than 24 hours, it started right back up without me having to do anything at all. If you go for the non-utube style overflow, then good luck as they are pieces of sh$t. Either drill it, or use a utube style of overflow (eShopps brand is highly recommended).

 

Most overflows are modified siphons, not straight siphons, so don't lose vacuum when you lose power.

Rather than go with a box, you could try some variations. I like the larger diameter PVC pipe to the bottom as an overflow "box".

You could check out this DIY variation for some ideas... the only time it has ever lost siphon was when my sump ran dry and was blowing bubbles in the tank (my kludged top-off didn't work so well). And that problem required my intervention regardless.

http://www.3reef.com/forums/i-made/vansiphon-125857.html

 

Thanks scadsobees that looks like a great design for our application. As for drilling the tank it would be ideal but the nearest glass shop is over an hour away and doing it myself just scares me. My next tank will defiantly be pre drilled. ill post pictures of the build as it progresses so hopefully the next guy can learn from my catastrophic mistakes ;D

 

well tried to upload a pic but cant for some reason. waiting for the glue and silicone to cure. cant wait to test it out. Went with 1 inch pvc for the piping and 3 inch for the bulk head and siphon chamber. I,m curious how many gph its gonna pull

 

YOu can see a non drilling option by looking at my DT vid in my sig.

You store bought/DIY boxes were not big enough for me, so I built my own stuff.

Works awesome, power outs are no problem, and I even have redundant failsafes like kinda like airplane systems do, to prevent floods, etc.

 

I think another reason for the box is for the surface skimming, with just a pvc tube going into the tank there wouldn't be any surface skimming. I built an overflow box that worked for a bit before it was totally plugged with algae and I had no way to really clean it. I now use one of the ones with two boxes and a u tube and seems to work fine. I have about 300-350 gph going through it with no problems.