A check valve is incorporated in the circuit in Figure 1 to allow free-flow in the reverse direction (i.e. to bypass the counterbalance valve when raising the load). Care must be taken if using a conventional relief valve for this application as at some stage of operation the tank port will be subject to maximum circuit pressure. This is not permissible with many relief valves. The counterbalance valve shown has an integral check valve. A separate drain connection from the spring chamber is unnecessary because the pressure section of the valve is inoperative when the T port is pressurized (flow is through the check valve). When it is counterbalancing the back pressure at T should be kept to a minimum.