Filter unit for a baseboard hot water heating system

In an improved filter unit for a baseboard hot water heating system, comprising in combination, a valve housing having an intake at one end and an outlet at its other end, an upward extension on said housing having a chamber containing removable filters, an upper end of said chamber having an opening closed by a removable screw cap having a downward element on its underside supporting a downward valve shaft extending through said filters, a lower end of said valve shaft extending through a wall below said chamber and into a water course chamber therebelow where a valve head on said shaft seats in a valve seat on an underside of said wall, a lower portion of said shaft being screw threaded and engaged in a vertical, threaded opening through said wall, and said wall having a plurality of passage openings therethrough opening out on said seat and which are closeable by said head when engaged in said seat.