Main shutoff valve - stop and waste

Plumbing · Distribution Piping In the House · printed page 265 (PDF page 266)

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Main Shut Off Valve for Plumbing – Stop and Waste Main Shut Off Valve Public Water Supply for Plumbing

Text in the illustration

stop and waste valves are not full bore valves
they are not common on new installations and are not permitted in all jurisdictions
these should not be used where the valve may become submerged since the waste creates a potential cross connection
floor framing
cold
hot
foundation wall
water meter
main shutoff valve
gas
gas water heater
bleed valve
water flow
stop and waste valve - has bleed valve downstream of valve (for draining water out of the supply pipes for repairs)
cross section

Generated explanation

A foundation cross section shows the incoming water supply passing through a main shutoff valve and water meter before rising to the cold-water distribution piping. A branch supplies a gas water heater, with separate hot-water piping leaving the heater. An enlarged detail shows a stop-and-waste shutoff valve with a bleed valve downstream of the shutoff, allowing supply piping to be drained for repairs. Notes state that these valves are not full bore, are uncommon in new installations, and are not permitted in all jurisdictions. The illustration warns against installing them where they may become submerged because the waste opening creates a potential cross connection.