and if so, what do you do to get the water to stop flooding out? TBSE, with thermostatic valve up-top. Even with the valve closed, hot water will continue to come in if you try to drain at top by loosening union. Try to undo bottom union and water also pours out, cold and then warmer. Thermostatic valve is sensotherm and valve is "MA". System has a pump with no off (BG Multihead G). Boiler and tank system. Any thoughts, gratefully received as this is inhibiting decorating no end.