#16 might do the trick but it is mainly used for patching. The setup time is just too long for a good joint. It has good gap filling properties if your joint isnt perfect.
I've built a few sumps and the best stuff is Weld-on #4. This has a set up time of under 5 minutes
Weld-on #3 is faster and sets up in 60 seconds or so. A bit too fast for large projects.
If you are doing any kind of joint make sure it is perfectly flat and use the pin method when glueing the joints.
This will assure a good strong joint with no bubbles.
If you need more info on the pin method email me at
parkerm@shaw.ca