Normally a sheepsfoot roller recommended. Look at the link below. It goes down to a normal D5. Your D4 LGP will be lower than that. Compare it to a sheepsfoot. Not even close.

http://extension.missouri.edu/webster/pond-seal.aspx

PS. found a D4 LGP cited.. 4.2 psi

Last edited by DNickolaus; 10/08/14 07:10 AM.