Which Weldon

[guppie]

I have to fix the seams on a plastic water holding tank which Weldon should I use?

[mcgyvr]

What type of plastic?..
What specifically needs to be fixed about these seems? Large gaps/cracks?

There are many kinds of weldon obviously and its the details that let you know which one is appropriate for your situation.
but all we know is you have a leaky plastic tank.

[guppie]

It is thin plastic, and it is attaching the top to the container, it has a seam all around it that I want to seal to hold water.

[guppie]

Anyone

[zachfishman]

Dependent completely on the type of plastic that tank is made of...

[mcgyvr]

how about a clear picture of said tank?