How big a hole for an overflow?

[Bec]

Hi all,

I want to turn one of my tank tiers into a drip system with a sump unit. It has four glass tanks that are about 1 1/2 foot cubes each, in a big pine stand. I have called the local glass shop and they can drill the tanks for me at a price of $10 each (as if I would bother to try for myself at that price). The maximum size they can drill is 26mm. What size hole is good and how do I attach the hose to the hole?

I have done a little reading and there is a dooverlackie that goes on both sides that can be attached to the hole (the name escapes me ATM) and a hose but I would not begin to know what size would be best for the hose itself.

Each tank is about 90 litres so that is about 400 litres for the stand, plus the sump itself (what size sump should I use). I am thinking of using a 3000 litre an hour pump (overkill? ) in case I end up hooking up the second stand (maybe I should just set them up independently and use a 1500 litre pump each…that way if I am only using one it would only require half the power etc. Also, I would halve the risk of contagious infection even though I am going to use UV’s).

Any brilliant suggestions greatly appreciated,

Bec

[SFF1]

Bec

I believe you're better off using the largest size overflow you can.

Water entering will be under pressure whether it is just by gravity or from the pump and as such the pressure will most likely be greater than that exiting via the overflow (which will most likely be only be by gravity).

Therefore the scenario to avoid is one where the water cannot get away fast enough through the overflow and you find that the tank will overflow. So I would say use the largest overflow you can which in the case is 26 mm. Remember there will always be some resistance in the tanks as water flows over and around obstacles. Bends in pipes/overflows also restrict/slow the flow of water as well.

Make sure your overflow cannot block up with debris as well as the end result will be a tank that overflows, followed by an empty sump and an aquarium heater that is no longer surrounded by water that will become a fire hazard especially if you use a plastic container as a sump.

Finally if you find the overflow isn't large enough an option might be to add a second overflow. Remember you can control the water going in with a tap therefore you can restrict it so the overflow isn't overloaded. UV sterilizers are also more effective with a slower water flow.

So to sum up, at a guess, the 26 mm overflow should be adequate but you will never know for sure until you test it as there are many factors to consider.

Best of Luck

Edited October 1, 2010 by MikeB

[Bettarazzi]

I think the dooverlackie you mean is a bulkhead http://www.aquaria.com.au/catalog/index.php/cPath/1_33. You can also find them at Bunnings in various sizes.

[fishbites]

Locally, bulkheads are a lot cheaper at one of the specialist plumbing and irrigation places - prices vary quite a bit so worth shopping round for them.... also look out for strainers that will screw onto the inside of the bulkhead to keep fish and other things from flowing down the tube....