[Crawlerm]

I'm curious as to what reaction occurs from mixing human urine, which I believe contains Urea, in seawater. In the toilet pipe of my bota there is a thick crusty residue which blocks the pipe after a while. I think the susstance may be Calcium something but don't remember enough Chemisty to figure it out. Can anyone help? I did a little experiment of mixing the two liquids and filtering out the residue, it was surprising how much of the white chrystals I got.
Thanks
Bob

[Arkcon]

I guess it can be a surprise.  To start with do the white crystals dissolve in plain water? That could be a useful hint. 

P.S. mammal urine contains the chemical urea, which get their name from each other.  But urine isn't only urea.  This is a common misconception.  People know urine ≠urea, but  still think all problems and question with urine revolve around urea.  As an example, often people expect the enzyme urease to remove the smell of urine, when it isn't the reason for the smell at all.

[Crawlerm]

I guess not as they precipitated out, I've thrown it way now so can't be sure. I'm assuming that the white precipitate (as picture) is the same as, or the basis  the crud in the pipe (picture attached). I looked up sea water in wikipedia https://en.wikipedia.org/wiki/Seawater but am not sure how it would react, I guess dissolved gases may also matter.

Thanks for your interest
Bob