Legal Question in Wills and Trusts in Pennsylvania

Sorry - I misinterpreted!

That is another issue - if that's what you want, then I don't know of any express prohibition unless water/sewage is controlled by your municipality and there is some local ordinance about putting things in the toilet (like a prohibition on flushing sanitary napkins because it screws up the water filtration systems).

Lots of people want their ashes thrown in the river or ocean - flushing down the drain is not all that different.

I would create a declaration of final arrangements (along with a will and healthcare power of attorney, living will and you should probably have a financial power of attorney too) where things like this can be spelled out so that your loved ones know that you are to be cremated and your ashes disposed of by this means.