Equalizer valve is a dirty fluid valve for sealing high differential fluid pressures in a drilling environment and methods for using such a valve is disclosed. One embodiment of the valve includes a seal cartridge having several openings for directing a fluid path through the cartridge, a spring connected at one end of the seal cartridge and extending through the fluid path, and a seal member connected to the other end of the spring. The seal is actuatable between an open position and a closed position so that it covers one of the openings in the seal cartridge when it is in the closed position, thereby sealing off the fluid flow through the seal cartridge fluid path. The spring provides a pre-loading force to the seal member so that the seal member always has sufficient contact with the surfaces surrounding the opening that the seal covers.