Drilling a large acrylic tank

M

mattsfishes84

New member
Quick question -

I may be coming across the opportunity to fix the issues of a large (~550) arcylic tank.

One of the biggest problems is circulation. There are no closed loops, and the main system pump plus the two tunzes aren't cuttin' it.

My biggest question:

After emptying the tank, will drilling the bottom panel of acrylic affect the structural integrity of the tank?

I intend to install 2 closed loop pumps. So there would be four holes, 2 drains, 2 returns.

The tank is viewable from three sides, so I can't drill the sides, only the bottom.

Thanks in advance!
 
Yeah.. but I'm talking about the bottom..
where all the weight of the rock is and such..
Understandably there is a lot of water pressure on the sides.. but I just want to make sure that when I get this bad boy filled back up with rock and water that the bottom, freshly drilled panel isn't going to crack.
 
I See the bottom being less of an issue than the sides. At least the bottom is supported by wood. The sides have no support. Im far from an expert in this field, but it seems safe to me. Especially since a lot of guys drill their bottoms of the acrylic tanks.
 
Drilling the bottom of a tank has never seemed like a good idea to me, though it seems to have gotten very popular lately. What do you do a couple years from now if the bulkhead begins to leak? No choice but to start over.

Drill the top third of the back panel, that way if you ever need to fix a leak, you only need to drain the top third. I'd hate to have to drain 550 gallons of water if you ever had a leak. Think long term, who knows how long those seals will hold up? I'm planning my tank to last for the next 10 years minimum. Also, water in the ocean comes from the top down or striaght on, not up from the sand. I've seen some strange growth where corals grew next to outlets coming out of the sand. Just my opinion. If you cant pull the tank away from the wall to drill the back panel, then I'd suggest more tunzes.
 
IMO there's no problem drilling the bottom, I'd just recommend using a quality Sch 80 bulkhead with the better gaskets and thread pitch and just plain beefier. Public aquariums commonly drill the bottom of their tanks and they are designed to last many years. A 10-20+ year lifespan is common in public aquaria and I've never had a tank "go" from this.

Some folks are not comfortable with this and I respect that but there are no structural issues if the tank is supported well and built soundly, and a good Sch 80 bulkhead will alleviate many of the problems with leaky bulkheads.

FWIW, I've never had any issues with Sch 80 gaskets degenerating over time. They either seal or don't seal and do not start to leak down the road and the times when they don't seal is due to not cleaning the area or gasket at time of installation. Most leaks and bulkhead failures are due to user error IME; particulate matter between surfaces, bad plumbing practices (poor job with Teflon tape and that sort of thing), once in a while someone overtightens them, these are evident and fixable on test fills. Once in a while they are just bad from the beginning and this is noticeable when you first get it, this is *very* rare though.

HTH,
James
 
Acrylics -
what would you consider to be "tight" and "overtight" on a Sch. 80 bulkhead?

Thanks for the help.. I can get to the one side panel.. although it would be tricky. But.. getting to the bottom isn't easy either.. I'm still not sure what I want to do.
 
<a href=showthread.php?s=&postid=12811271#post12811271 target=_blank>Originally posted</a> by mattsfishes84
what would you consider to be "tight" and "overtight" on a Sch. 80 bulkhead?
Click to expand...
IME, anything more than hand-tight is not necessary. Some folks like hand-tight plus a 1/4" turn but I don't find it necessary. Perhaps I have strong hands but never had a bulkhead leak from just hand-tightening. For the better brand bulkheads (Spears & Hayward), the thread count is so low and the threads designed in such a way that it would be tough to actually damage the fitting by just screwing the nut on. Hope this makes sense.

When I mentioned "overtightening", what I meant was folks overtightening the male pipe thread that goes into the bulkhead body itself, thus cracking the bulkhead. Sorry for any confusion.

HTH,
James
 
i have 5 holes in the bottom of my 18'x30"x4'.....no problems....i wanted to drill the sides but couldnt find a bit to handle 2" acrylic
 
And can anyone recommend a good 1.5" hole drill bit for acrylic? I have the standard wood hole bit set, but I don't know if those teeth are too agressive.
 
I've drilled my share of acrylic using Lenox hole saws from Lowe's. As long as you take it slow.. and DRILL A PILOT hole.. you'll be fine. Don't push.. don't force it.. but also don't melt it.. :-P
 
this is just my opinion. If the tank is new and you drill it there is no problem. But if the tank is used ive been told that the acrylic is more brittle. I actualy had a used acrylic tank and the LFS would not drill it for me. They told me that they dont drill used tank. If i brought a brand new one to them they had no problem drilling it. Because old acrylic with time get brittle. dont know what hea meant though.
 
Yrs ago this was more of an issue. The newer acrylic formulations came about about 15 years ago and don't yellow like the old stuff and don't get brittle like the old stuff, it might a little but not nearly what they might be thinking. So basically if the tank is less than 15 years old, it's a non-issue. For that matter I've got tanks out there that are ~20yrs old that I wouldn't hesitate to drill if asked.
FWIW much of the problem was a product of the reaction between UV and Cadmium. Since Cadmium has been removed from the resin - not a problem.

OTOH, kinda odd that they don't mind voiding your warranty on your new tank but won't drill an old one.

HTH,
James
 
Four holes in the bottom of my 1" acrylic tank. No issues whatsoever. I had my wife stand on the bh's while I hand tightened them from below.
 
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