cracked sump

[jc]

I was setting up a new tank and I over tightend a bulkhead on the side of my acrylic sump. I noticed a crack about 1/2" coming out of the bulkhead. Their does not appear to be a leak, but I am worried. What can i use to seal the crack so it does not grow?

[TroyPham]

weldon will work. any acrylic shop should have it. I believe it's acrylic acetate

[matt]

You can try putting a patch of acrylic over the cracked area; the best cement in this case would be weldon #40, which you might have to mail order. If you can wait a couple of weeks, I can fix it for you if you bring it over to my house. Just running weldon #3 in the crack won't do much, and weldon #16 might stop the leak (there is one, believe me, or there will be, if the acrylic is cracked through!) but will do little to strengthen the area so that the crack won't spread. Acrylic's unlike glass or wood in that the crack is not likely to spread on it's own; that's the good news. The bad news is that it's in an area of stress, because you have the bulkhead, and I assume plumbing attached to it which will put some torque on the area.

[jc]

I can feel the crack on the outside, but not on the inside so I assume its not cracked through. I wish I could take it to your place but I just had a hell of a time putting everything together and finally no leaks. I don't want to move anything. Does any store carry weldon #40? So I just need a small square of acrylic and bandage it over the crack with the weldon. Does it go on the outside, inside, or both? What size of acrylic bandage do I need, 1" square would cover the crack for sure but does the acrylic need to be a certain width?

[matt]

If it's a crack, I bet it goes all the way through even if you can't feel it, but I could be wrong. It probably doesn't matter, the fix is the same. I'd put a patch on both sides just to be sure. Weldon #40 is tough to find locally; I get it mail order at a place called plastix in New Mexico. You could try weldon #16, which you can get locally, it's just not as strong. As long as the patch completely covers the cracked area it's okay. Probably what I would do if it were mine is to put a big patch covering the whole area including the hole; maybe about 4" X 4", on both sides, then re drill the hole for the bulkhead in the same spot. If you're using a 1" bulkhead, you might try drilling for a 1.5" bulkhead. Actually, if you could re-drill the hole for the larger bulkhead and the new hole completely cuts out the cracked area, you could forget about the patch. Thinking about it, that would be ideal if you can make it work.

Here's the best way to drill an acrylic sump for a bulkhead; it takes a router and a 1/4" flushtrim bit, plus a hole the size you need in something for a template. You use double sided carpet tape to attach the template where you want the hole, then flushtrim around the inside. You'll get a perfect hole with no chance of cracking or melting the acrylic. The only thing is you need to make sure the template is taped in place solidly. The heavy duty carpet tape works great; I use it all the time. I have an acrylic template with a hole in it for a heavy duty 1.5" bulkhead you can borrow, and an old flushtrim bit that's still okay but too dull to use on 3/8" cast. Let me know if this will help you.

[jc]

o.k. i'm going to call regal plastics tomorrow and see if they have the weldon #40. If not I will order it online. I have some 1/4" thick pieces of lexan around, can I use these to patch the crack when the weldon comes in? Also how long does the weldon take to cure? I would like to lower the water level in the sump, dry the sides and apply the fix. Will this work?

[matt]

I don't know about the lexan, but there's a chart on the IPS website that might tell you if weldon#40 will bond it to acrylic. The #40 takes a couple of hours to cure, but you might want to leave the area dry overnight. Regal plastics will probably not have weldon #40 in stock; if they do by some chance it's likely that it will be old; the stuff has a shelf life of one year past the date stamped on the box.

If the 1.5" bulkhead idea will work, why not try that? You can just put a bushing in the bulkhead to bring your plumbing down to 1".

[jc]

I used weldon #40 with a square of acrylic to patch the cracks. There was another one towards the bottom of the bulkhead that I didn't notice. Well I decided just to patch the outside of the cracks since they were not leaking and I just wanted to add some extra support. The next day the cracks doubled in length. Why would they do that after I used the weldon and put the acrylic over them? They still are not longer than the patches and are not leaking. Did the weldon expand in the crack and make them bigger?

[matt]

I have no idea why that would happen. Weldon #40 doesn't expand as it dries; it shrinks. If you can wait a couple of weeks and get it to my house I'll be glad to take a look. I assume you put the patches on but did not put the bulkhead in, right? Also if you clamped the pieces tight I suppose that could have stressed it in some way, but I'm just guessing. If the weldon #40 is now dry and the patches are completely covering the cracks, it should be okay.

[jc]

I didn't clamp the pieces. I just held them in place for a bit till the glue got a little hard. I didn't remove the bulkhead I just put the patches on as close as possible to the edge of the bulkhead. I have been running the pump all day and so far so good.

[matt]

Sounds like you glued on the patches right; hope it works out. BTW, did Regal have #40? What size did you get, a pint or the small 4 ounce bottle? If you're going to hang on to it, take the box it came in and put the whole thing in a freezer bag (to keep the smell in) and store it in your fridge; it'll last ALOT longer. You have to let it warm up to room temp before using it.

If it starts leaking at some point (let's hope not!) and you want some help just let me know.

[jc]

I had to order the glue online from craftics.com. Thanks for the help, i'll let you know if it leaks.