So a little research shows that dispersant acts like the salts in your water softener system, exchanging one ion for another in clay due to the large concentrations of a different ion (Sodium exchanged for Calcium for example). Calcium ions in clay can from micro-globules due to attractive forces (gritty clay). Replacing them with sodium ions causes the globules to disperse into a uniform material which is not clumped, which acts as a much better sealant (slimy clay).
So with that thought in mind, and enough clay, salt dumped in at a leak site may actually have a sealing effect, but only in some cases. This actually may work for me if my pond continues to seep. I know my clay clumps due to high concentrations of crushed limestone in the soil, but it is also the reason my water clears so nicely so I am afraid of exchanging one problem with another.
By dumping salt un-dissolved down into the potential leak site, you would achieve the high concentrations needed for the ion exchange in the clay of concern without needing to treat the whole pond. The key is knowing where the leak is. Otherwise I think that ESS-13 (I cannot quite remember the name) may be more effective at pretty much doing the same thing.
Look up the different salts available, but softener salts of various types should be usable and relatively cheap. Just have to check out what is does to some samples of your pond water and bottom clay before applying. Maybe the old bucket test.
