The invention belongs to the technical field of domestic water, and particularly relates to a
delay water outlet valve for a
pipe-in-
pipe and a hot
water discharge system thereof. The
delay water outlet valve for the
pipe-in-pipe comprises a
water heater, a liquid
inlet valve and a pipe-in-pipe pipeline, the
delay water outlet valve is arranged at the
tail end of a
branch of a pipe-in-pipe pipeline through a pipe-in-pipe joint, the delay water outlet valve comprises a valve body, the valve body is provided with a liquid outlet end and a pipe-in-pipe connecting end, the pipe-in-pipe connectingend is provided with an inner flow passage and an outer flow passage, and the liquid outlet end communicates with the inner flow passage and the outer flow passage through an inner cavity of the valvebody; the inner side of the pipe-in-pipe connecting end is provided with a delay sealing part separating the inner flow passage and the outer flow passage, the inner cavity of the valve body is provided with a damping
piston and a first reset part providing elastic force, the damping
piston is arranged on the outer side wall or the inner side wall of the delay sealing part, and the outer flow passage or the inner flow passage is sealed; and when an internal medium pushes the damping
piston to separate the delay sealing part, the delay liquid outlet of the flow passage where the damping pistonis located is realized. The delay water outlet valve for the pipe-in-pipe and the hot
water discharge system thereof have the advantages of small cold water emptying amount, high hot water outlet speed and the like.