I have a Weil-Mclain EG 35 hot water boiler. The hot water shutoff valve underneath the bathroom sink has failed and isn't stopping any water no matter how the handle is turned. I'm not sure I'm understanding the setup correctly, but i.r appears that the cold and hot pipes to that particular faucet run directly off the boiler, and I'm not seeing another plane to shut off the hot water. What am I missing? Is there a way to shut off the hot water that I'm missing? I included pics of the setup.