is secured thereto to accommodate a header pipe fig5 is a perspective view of the optional inner supports 44 of the present invention the present invention provides optional inner support members 44 for placement within the housing 26 the separate inner supports 44 are used as necessary and may not be required in an application where support can be built into the chamber fig6 is a detailed view of the optional inner support 44 of the present invention the present invention provides optional inner support members 44 for its drain field design the drain field design comprises a housing having a base forming support walls and top cover plate end plate and a channel having drain apertures extending the length of the channel wall both sides and each unit lockable to other units having header pipes at both ends the optical inner support members 44 are used as necessary and may not be required in an application where support can be built into the chamber fig7 is a detailed view of the end plate 36 of the present invention the present invention provides end plate members 36 for its drain field design the drain field design comprises a housing 26 having a base forming support inner pipe and top support end plate members 36 and a channel having drain apertures extending the length of said channel wall and each unit lockable to other units having header pipes at both ends the end plate 36 has.