A four-way diaphragm valve for controlling flow of a gas or liquid comprising: a valve housing having a first substantially circular valve chamber and a second substantially circular valve chamber; first, second, and third channels opening into said first substantially circular valve chamber, said second and third channels being separated from said first channel by a respective one of a first and a second substantially parallel valve seat means extending across said first substantially circular valve chamber, each valve seat means providing a substantially linear valve seat for a first elastic diaphragm, said first elastic diaphragm being adapted to be moved into and out of sealing engagement with one of said first and second valve seat means;Bellows Seal Valves first and second individually operable control means, each operable control means being adapted to press a respective linear portion of said first elastic diaphragm against a respective valve seat means to thereby shut passage of fluid between said first channel and at least one of said second and third channels, each operable control means being adapted to positively raise a respective portion of said first elastic diaphragm off of a respective one of said first and second valve seat means to open fluid flow between said first channel and at least one of said second and third channels; a fourth channel opening into said second substantially circular valve chamber,MUD VALVES said fourth channel communicating with said first channel through an opening in said valve housing, said fourth channel being separated from said first channel by a third valve seat means extending across said second substantially circular valve chamber,Reducing Valves said third valve seat means providing a valve seat for a second elastic diaphragm, said second elastic diaphragm being adapted to be moved into and out of sealing engagement with said third valve seat means; and third control means being adapted to press a respective linear portion of said second elastic diaphragm against said third valve seat means, thereby to shut passage of fluid between said first channel and said fourth channel, said third control means being adapted to positively raise a respective portion of said second elastic diaphragm off of said third valve seat means to open fluid flow between said first channel and said fourth channel.

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