[QUOTE="Lisak1, post: 243195, member: 6145"]. The bog is 4x6 and 4 feet deep - much deeper than most would recommend.[B][U] The bottom 2 feet contains the manifold and vault and larger (softballs sized) rocks[/U][/B]. Then there's a layer of gravel (I think it's called number 10 construction gravel) then there's about 18 inches or so of pea gravel. Works great for us. [/QUOTE]\nWould you be able to discribed in more detail how you created the vault in the bottom of the bog. Is this a hollow chamber that you created to allow muck to settle in?. The reason I'm asking is the main negative criticism I have read with bogs is the build up of muck in the pea gravel creating channeling and an anerobic environment.. My thought is to create a hollow area under the pea gravel with a drain and valve to occasional back flush the muck from the bog.