Sime Gas Valve 6243821 is a special mechanical device which is designed to control the pressure and flow of gas to the Sime Gas Valve 6243821 . This is a mechanism that controls the flow of gas to the burner, depending on the model of your boiler, it?s controlled by an electrical signal coming from the printed circuit board (PCB). Heatingspares247.com is one of the UK's largest independent Boiler Parts & Heating Spares Stockist, We specialise in the supply of Genuine Spare Parts along with all the leading manufacturers. Services available are trade counter pick up, Next working day standard delivery, next working day AM delivery and Saturday delivery. We also operate same day express delivery service. Our Opening timers are Monday to Saturday, 8AM to 5.30PM Heatingspares247.com is an Approved Boiler Spare Parts Stockist, and we guarantee to supply Genuine Heating Spares from the Boiler Manufacturers.