SAUNIER DUVAL SD 623 COMBI BOILER PRESSURE AT ZERO BAR HEATING OK BUT NO HOT WATER. FILLING LOOP PESSURE LOOP THERE ARE 2 BUTTERFLY TYPE DEVICES ON EACH END OF LOOP +ON THE TOP MOST CONTION JUST ABOVE BUTTERFLY DEVICE IS A CIRCULAR PIECE STICKING OUT WITH 10MM NUT FITTED
HOW CAN I GET PRESSURE BACK UP

RON GOLDSMITH, July 2008

one of the butterfly type things is in your mains water supply the other is to your central heating open both and watch the pressure rise to 1or two bar this should help

daddy c, July 2008