# drilled or overflow return?



## Elle (Oct 25, 2010)

I'm very slowly starting to plan for my ultimate tank (300 gallon acrylic with wet/dry filter). However, one issue is deciding whether to go with an overflow or have the tank drilled.

I'm not a fan of drilled tanks...one reason it's taken me so long to set up my current large tanks is because of the need to plug the holes that have been drilled in the damn things because they don't line up with my stand. With an overflow, the hoses can go where I need them instead of trying to line up the tank holes with the stand holes.

The other is that the more holes, the less integrity, or at least that's JMHO. 

Can anyone chip in with the pros/cons of each option? This will be a freshwater tank, so no need for a skimmer.


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## Captured Moments (Apr 22, 2010)

I believe the general consensus is that having your tank drilled is better than an overflow box system. One of the main reason is reliability in that it does not rely on a siphon to maintain prime as in the case of the overflow box. In the latter, there is the possibility that you could loose prime and thus the drain will not work and you could risk an overflow of your main display tank if the return pump from the sump keeps pumping water back into your display tank. With the tank drilled, the drain simply relies on gravity to overflow the water from your main display tank to the sump below. Obviously if your drain gets clogged up with debris or plant matter, then you will have a problem in either system. I read that some people have set up their sump in such a way that the return pump sits inside a return chamber that will run dry should the water level in the sump fall past a certain level, in the case of the drain from the main tank not providing the water to the sump. Run dry, no water, no pumping, no overflowing problem but the pump can be damaged in this case. Also, some people run constant aqualifter pump on the overflow box to maintain prime on the siphon but I have no experience with that so I don't know how well it works.

With either system, the preventive measure is to install a pump stopper overflow kit. Basically it is a system of float valve connected to a relay switch that stops the pump should the water level rise past a predetermined level on your main tank or the other way around should the water level drops below a certain level in your sump. Depending on how your sump is designed and the operating water level, it may be best to have the switch control in the main display tank to prevent overflowing.

You can have the tank drilled on the back panel as opposed to the bottom. That way you don't have the problem with lining up the holes with the stand provided you have enough clearance at the back.

I am running a DIY PVC overflow system on my 135 gallon which is not drilled. You can take a look at my thread if you like. It's not the most attractive because of the PVC pipes but it works very well. It has been running for almost a year straight and it has never lost prime. Mind you for safety, I have installed a pump stopper kit from Aquahub. It is worth the measure of safety and better peace of mind.

A number of people here have drilled tanks so they can advise you better on the merits of it and address your concerns about "integrity", meaning leaks?


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## SeaHorse_Fanatic (Apr 22, 2010)

I would go with drilled myself. Don't use a diamond drill bit though, the acrylic heats up, melts and coats the drill bit


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## macframalama (Apr 17, 2012)

drilled elle i have had 2 flood in my house both a result of power outages and the siphon breaking in the over flow box and the damn thing not priming properly before the return pump pushing the contents of my sump over the top of my tank, bean animal overflow systems, and with an acrylic tank i wouldnt worry about structural integrity there tough as nails , ever been to a hockey game same material stops pucks at 100 mph


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## macframalama (Apr 17, 2012)

i have both drilled on the bottom and drilled on the back, and i much prefer the bottom drilled, because you can make your "stack" easily, you can adjust the tanks water level by pvc placement and over all there super silent, and the pull straight from the surface, just build your stand any way you want, then drill your tank , then put your tank on the stand mark out your holes , remove the tank , drill the stand, problem solved.. also anothe benefit of the bottom being drilled is when the pump stops so does the water no need for a siphon break


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## macframalama (Apr 17, 2012)

SeaHorse_Fanatic said:


> I would go with drilled myself. Don't use a diamond drill bit though, the acrylic heats up, melts and coats the drill bit


speaking from personal exp lol


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## gklaw (May 31, 2010)

I am running both SW on overflow. All my FW tanks have been drilled. Planning to replace both with drilled. 

Although I only had one incidence over 14 years - overflow due to snail got into siphon which could have been easily prevented.

Drilled overflow is much less hassle.


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## Elle (Oct 25, 2010)

OK, good to know! If I go with a new tank, it would probably be drilled at the back...but I do have one tank with predrilled holes in the base.It just depends if the holes match with the stand.

When you say "stack" for a bottom drilled tank, how does that work with sand substrate? How far above the substrate is the intake? I'm having problems picturing it.


Thanks guys!


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## macframalama (Apr 17, 2012)

okay so if the holes are in the bottom , there will be a bulk head fitting through the acrylic, then the bulk heads have a male to slip pvc adapter then the pvc goes up to the top of the tank, the length of the pvc "stack" dictates where your water level will be,, its the same as my 120 gallon set up , elle i will happily take pics and show you what im talking about but the damn bears destroyed my garbage cans and im cleaning my yard, in addition to that mess i sliced my finger open on a broken piece of glass so .. if you gimme an hour and pm me your email addy i will send you a bunch of stuff lol


not a great start to the day but hey .... coffee is on now lol no where to go but up


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## Scherb (Feb 10, 2011)

I would like to see some of the pics too mac. Please and Thanks


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## charles (Apr 21, 2010)

Elle, I ran overflow box for a number of years. Here is something that I can tell you:

Overflow box system:
- a U-tube type overflow box (not the run using the air pump one) will not lose siphon unless you physically remove the u-tube and let the water out. As long as the U-tube are in the box and setup properly, you will not have a problem
- If your return pump is pumping too much water back to your tank, if that is your concern, install a adjustable let out inside the sump just above the return pump so you can adjust how much water going into your main tank. You also gain an advantage of extra air in your system as the adjustable let out usually is above the return pump water line.
- Don't have drill the tank.
- Generally need smaller space than an PVC elbow if your tank is drilled on the back. A good overflow box is normally about 3" space needed at the back. 

A drilled tank
- no need to worry about losing sipon
- need a little more space if you are planning to use 1.5" pvc at the back of the tank. Unless you are planning to build a skimmer surface to cover the bottom drill, which you can flush mount your tank to your wall.
- need to drill the tank, in your case acrylic is no big deal, but it is perm.. 

In both case, you need to see how much your sump tank can handle. In most flooding case, it is almost always these problems, sump is too small, improper matching how much your main tank can drain out. Your skimmer will take about 1" of water, but your return pipe will continue to back siphon to your sump if the power is out (this apply to both drill and overflow system). Most setup I have seen, almost always have the return pipe at least 2-3" under the water line. It is ok if you have a big sump and your sump should be 1/3 fill only.

Think about this example... say your main tank is 72"x24"x24" = 180g and use a 33g 36"x12"x18"H sump. Your skimmer is 1" and your return pipe is 3" underwater.

And your 33g is half fill.
3" of water in your 180g = 22g of water siphoning back to your sump. And if your sump is half filled already, you will flood.

You can install a one way valve on the return. Get the clear one so you can see if there will be thing clog in it.
You can get a bigger sump.
You can submerge the return higher up instead of 3", you can do 2" or maybe 1".


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## macframalama (Apr 17, 2012)

sure, its so hard to explain and i suck at trying to type what i mean lol, i will post some pics in a bit...


Scherb said:


> I would like to see some of the pics too mac. Please and Thanks


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## Elle (Oct 25, 2010)

Thanks Mac! I pm'd my email, but if you can post them here I'm sure lots of people would be interested. Charles, I like the idea of the return valve.


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## macframalama (Apr 17, 2012)

will do... i can post how i did the bottom drilled 120 , and i can post how i did the back drilled on my 180, but i will say this i HATED my overflow box, never again, i actually stole the sump from my 170 and took off the overflow box 2 days ago because i am tired of it, worst part is its all really nice stuff, made by cpr, but after having to failures i have trust issues with it and its not worth the head ache


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## Scherb (Feb 10, 2011)

macframalama said:


> sure, its so hard to explain and i suck at trying to type what i mean lol, i will post some pics in a bit...


Cool, sounds good


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## macframalama (Apr 17, 2012)

alright so we dont get confused im gonna put a few pics up to explain what im talking about






that is a bulkhead as i know it , so this is what would be going through the bottom of the tank..then you screw in one of these






, its a male to slip fit adapter, the you take a standard piece of pvc, and you put it in the male slip adapter and put it to the desired tank water level height so just a little bit below the black rim on the tank, so when your return pump, pumps water from the sump as the water rises it goes down the pvc and returns to your sump.


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## macframalama (Apr 17, 2012)

on the under side of the tank, you can get threaded adapters aswell that will screw over the top of the bulk head fittings underside , then use a small piece of pvc on either side to a slip fit ball valve






, from there you have a few choices on what you can do you can either run t inlets to your sump which i prefer so you can run 2 filter socks on either output or you can run the 2 "drains" from your tank together and have one larger drain but the problem with that is the 2 running into 1 requires some planing because 1 inch pvc can only handle so much flow,

also having the ball valves on both drains if you find your having water noise you can just slightly adjust either side till its silent, and for your return i just use flex tubing and a diy spray bar outta pvc or a piece of an old fluval or whatever, im sure there are a million ways to go about getting the same results but this is how i have done mine and i have had zero issues at all, and my way is cheap which is my favorite part, the main thing you need to make sure is that both "stacks" are the exact same size otherwise one side will be doing the bulk of the draining and thats counter productive..

i will take some pics of my tank but the darn camera is dead so i cant , but this is the best i can do without the camera,.. i hope what im saying makes sence because it does in my head however im not a wordsmith lol..


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## tony1928 (Apr 22, 2010)

charles said:


> You can install a one way valve on the return. Get the clear one so you can see if there will be thing clog in it.
> You can get a bigger sump.
> You can submerge the return higher up instead of 3", you can do 2" or maybe 1".


I'm setting up my sump as we speak and I'm getting one of those check/swing valves as well. The clear one is great as you can visually inspect it from time to time. I'm going to install a valve right about it so that I can shut the water off, remove the check valve and clean it once a year. The alternative was to build a huge sump that could accommodate the back siphoned water. For the valve above it, I think I'm going to use a gate valve / blade valve instead of the usual ball valve. Those things are usually very hard to turn and I don't want to risk putting so much stress on the plumbing. Good luck with your plans! For me this is the best part!


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## gklaw (May 31, 2010)

Hey Elle:

Don't forget I still have Tony's old 100g sump


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## macframalama (Apr 17, 2012)

red arrow is the bulkhead , 
blue arrow is the male to slip fit adapter and the
green arrow is standard 1" pvc pipe 







the teenage mutant ninja turtle green arrow show the standard 1" pvc pipe at the top near the tank lip and this is how you set your water level, obviouslly as the water is pumped from the sump it will rise up the tank level and then the water will crest the top of the pipe and flow down, and its very very quiet






yellow arrow is the bottom of the bulk head from the under side of the tank , and the light blue arrow is the 1" pvc slip ball valve


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## macframalama (Apr 17, 2012)

and from here you can see the ball valve and from there it is just a straight pipe to my sump where a filter sock catches the debris


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## Elle (Oct 25, 2010)

Thank you Mac, that totally makes sense!

Gordon, I don't think I can fit that sump under my stand, sadly.


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## macframalama (Apr 17, 2012)

100 gallon sump would be so sweet , i just picked up a 75 gallon im gonna turn into a sump for my new 180 gallon, 3pm today i get to go get it,pretty stoked.. i also found a 90 gallon above tank sump that i almost grabbed lol... but i chickened out .. dont wanna push it to far wifey might kill me ... wasnt that long ago the awful word "downsize " was being thrown around lol..


Elle said:


> Thank you Mac, that totally makes sense!
> 
> Gordon, I don't think I can fit that sump under my stand, sadly.


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