Some Acrylic questions

[IPT]

So I have some really old Weld on 4. Does that stuff go bad? I tried it on a thin little test piece and it seemed to bond.

I know acrylic does not bond very well to glass with silicone but for an overflow it should work fine (I'm not building a tank or even a sump. Just a box that will be in 5 inches or less of water and generally have nearly equal pressure from both sides most of the time). I'll butt the front wall up to the bottom piece and maybe even give it two sides so any pressure it does have on it will not be loaded to the silicone (if I only used a 3 sided box and expected the silicone to hold the horizontal front to the perpendicular side wall). It's 1/4 inch.

Surely some of you guys have done this without issue? The weld on will keep it together, I just need to silicone to hold it in place and seal it off.

 

[sleepydoc]

No idea on the Weldon - but I'm guessing it will be fine.

As far as the acrylic bonding question is concerned, silicon will work to wedge a piece in place. Imagine putting the silicone in, letting it dry then placing the acrylic pieces in place. If it will stay because of the placement, you are fine. Having equal amounts of water (and therefore little pressure) actually works against you, since the water pressure generally works to hold it in place.

Generally silicone will work for a coast to coast weir, but not for a box, which I believe is what you are using. A better option is to make the box 5-sided and cut a hole to match up with the bulkhead hole in the tank. You can then either have the flange (& rubber gasket) on the outside of the tank, or put a 2nd rubber gasket between the box and the tank, so the "sandwich" will be bulkhead flange-gasket-overflow wall-gasket-tank wall-bulkhead nut when viewed from the side,if that makes sense.

 

[IPT]

Generally silicone will work for a coast to coast weir, but not for a box, which I believe is what you are using. A better option is to make the box 5-sided and cut a hole to match up with the bulkhead hole in the tank. You can then either have the flange (& rubber gasket) on the outside of the tank, or put a 2nd rubber gasket between the box and the tank, so the "sandwich" will be bulkhead flange-gasket-overflow wall-gasket-tank wall-bulkhead nut when viewed from the side,if that makes sense.

Hm, that seems counter intuitive. So a piece of plexi running side to side with only a bottom and front (a weir) would hold (with silicone being the only support for the face against the tank water force) but a box with two rigid sides to fight that force wouldn't hold? Am I interpreting your response correctly or am I missing something? We're talking about using the weld on to construct all the plexi pieces and then just silicone to hold it to the wall, yes?

The full box with all the gaskets is an idea but that seems to have more opportunity for leak points. I also have 3 holes drilled for the overflow system so now we're looking at 6 gaskets.

 

[IPT]

Well, the glass store is cutting all the pieces for about $35. I'll just play it safe and do it with glass and good old silicone.