92
Function
The drain valve uses the water pressure in the
cold-waterinlettoclosethevalve.Afeedhose
is connected between the water inlet and the
control valve.
Whenthecontrolvalveoperates(drainvalve
shouldbeclosed),thecontrolvalveopensthe
waterpressureontothefeedhose,whichiscon-
nectedtothelowerpartofthedrainvalve.When
the lower part is filled with water, the lower part
diaphragmpushesupthepiston.Thepistonlifts
the pressure plate against the drain valve rubber
diaphragm,whichinturnformsasealagainst
theouterdrum,effectivelyclosingthevalve.
When the drain valve should be opened, the
control valve changes position to allow the water
pressuretothelowerpartofthedrainvalveto
close, instead opening the return hose to the
drain. The pressure plate recoil springs pull the
pressureplateback,uponwhichthepistonis
pressedbackintothecylinder.Thewaterfrom
thelowerpartisfedthroughthefeedhoseand
the control valve to the drain.
2
Drain valve
3359
8
1
2
3
11
10
9
6
5
4
7
2
12
101772
 1. Feed hose
 2. Controlvalve
3. Feed hose
 4. Returnhose
 5. Upperpart
 6. Rubberdiaphragm
with drain connection
 7. Pressureplate
 8. Recoilsprings
 9. Cylinder
10.Piston
11.Diaphragm
12.Lowerpart
Principal
diagram