drain valves have some special features like:-
Fully Automatic - No Maintenance.
Manual Test Switch.
Manual Drain at power failure
Indication for Valve Healthiness
Easy to replace.
Glass filled nylon coil former.
'O' Ring seal on cycle adjustment pots to ensure weather proof sealing
Small compact resistant ABS Timer.
18 Months Warranty.
No tool required to replace timer.
small,2kg to 5 kg.