Glueing Acrylic overflow inside glass tank

[ReefStar]

I am going to drill the bottom of the AGA 180 near one of the short sides. I will then be installing an internal acrylic overflow to the glass side wall. I have heard that glass and acrylic do not always bond. Has anyone had experience doing this, and if so, what recommendations do you hvae to make sure the joint does not come apart.

Thanks!

 

[jamesw]

I have glued acrylick overflows into glass tanks before. Heck, all of the Oceanic RR tanks are done this way and they work great and last and last.

Use silicone to glue in the overflow. USE A LOT. Make a big bead on the face of the acrylic and glue it in. Then run a big bead up the outside and "fillet" that w/ your finger to make a big rounded fillet. Do the same at the bottom.

Good luck!
James Wiseman

 

[dizzy]

Joe I use Dow Corning 795 a construction adhesive. You can get it in black and use black acrylic for the for the overflow. The clear 100% silicon does not adhere to the acrylic very well. It my understanding that 795 has long been used in aquarium construction. Probably not going to find it at Home Depot so check with other building supply or glass companies. Call Dow for the name of the closest dealer in your area.

I always run a stand pipe at least half the way up the height of the tank (inside the overflow) just in case it did fail and then the tank won't totally drain down. I use 1.5" bulkheads most of the time. Also be sure to notch your acrylic piece for the silicon seams of your tank to make a better fit.

I have safely used this product in similar applications, but use at your own risk.

 

[Nelliereefster]

I recommend not putting the overflow at the end, but rather in the middle back of the tank. In the middle you can split the return pipe flow to go to both ends of the tank. If it returns from only one end, detritus will seek the low flow area and accumulate. Splitting the flow in the middle of the tank allows you to place powerheads on the ends to counterflow and create better turbulence -which more closely simulates "wave" action.

I agree with the silicone option. If you use the hardware store kind, allow it to cure for several days before adding water. The standpipe idea not only protects against drainage in the case of silicone failure, but will also dampen out the overflow noise. Overflow kits are available that have a float core for the stand pipe. I think they work pretty well. Bio-balls inside the overflow are also an option.

 

[aquarist=broke]

I recommend not putting the overflow at the end, but rather in the middle back of the tank. In the middle you can split the return pipe flow to go to both ends of the tank.

Thanks for the idea. I am getting my 50 gal. drilled on Sunday, and was going to do it on one corner, but now I am going center way...Thanks!!

 

[adamsaquatics]

Whatever you decide to do make sure the overflow is designed so the water pressure is forcing it into the tank. Do not rely on the silicone to make a strong joint...it will only make it waterproof. The corner overflow is best because the water forces it into the corner.

Make sure the surface is super clean and the acrylic edge is flush with the surface of the glass.

A center overflow shaped like a U should be supportedacross the back as water pressure will be pushing in along the glass.

Just some things to think about...please keep us updated on how things went...George

 

[Nelliereefster]

Not sure what the last guy is trying to say but...

There should not be any "pressure" on an overflow box from the pump or tank, here's why.

The O/F is nothing more than a box with slits cut at the top. In the bottom of the box, two holes are drilled, one for the outgoing water, one for the pump return.

In the hole that will be he outgoing drain, you'll want to fit a standpipe that will stand up into the box at least 2/3's the height of the box (siphon protection and noise reduction) Since there will be a water colum inside the box, there will be very little differential pressue across the box wall. All the box is doing for you is making sure the water that drains from the tank is skimmed off the surface. This is optimal since the surface tends o accumulate a protein layer which inhibits gas exchange and reduces light penetration. Even if the box seal wasn't perfect against the aquarium wall, as long as all the pipe fittings are secure, it doesn't matter -provided the standpipe is tall enough!!!

The other hole is where the pump return will come into the tank. Using flex tubing makes life a little easier. What you want to do is bring in the pump return thru the bulkhead fitting then "T" it off to the top sides of the box so that holes drilled in the top of the O/F box face the "short sides" of the tank. As you're looking at the tank from the front, you'll see a O/F box in the center back, with two overflows, one going left, one going right.

Recommend at least 1-1/4" (1-1/2" is better) drain hole, and 3/4" pump return. You'll need 4 bulkhead fittings, 2 for the holes on the aquarium floor, and two for the O/F box where the "T" pump returns come thru the box wall into the tank.

This configuration is, in my opinion, the better choice, because it more evenly distributes flow over the entire tank. Placing powerheads in the opposing corners is a must.

 

[adamsaquatics]

It's sometimes hard to explain without pictures, diagrams, smoke and mirrors...and of course a prop girl with a short skirt is always a big help!

I was just trying to point out how the tank water pushes the dam into the glass corner. The more pressure pushing it, the stronger it is, and the silicone only seals it. Never rely on silicone for strength.

The Hoover Dam is built on the same principle, also some old stone bridges use this technique...minus the silicone!

I did not explain the plumbing, which you followed up on in great detail...Job well done.

I'm interested in finding out how all this works out as I have a 150 up and running without a built in overflow. I cant believe I bought it to save money...$400 vs $800 for an Oceanic with built in duel overflows. George :roll:

 

[skilos1]

its not really good to just say it doesn't matter if the overflow is not completely sealed because if the pump fails and the tank continues to leak at the bottom of the overflow then the tank will drain all over your floor until the water gets below the stand pipe that siphons the water down.

Even if the box seal wasn't perfect against the aquarium wall, as long as all the pipe fittings are secure, it doesn't matter -provided the standpipe is tall enough!!!