16. =_Don’t_= fail to blow off steam once or twice per day according
as the water is more or less pure.
17. =_Don’t_= fail to close the blow-off cock, when blowing off, when
the water in the boiler has sunk to one and a half inches.
18. =_Don’t fail_=, while cleaning the boiler, to examine and clean
all cocks, valves and pipes and look to all joints and packings.
19. =_Don’t_= commence cleaning the boiler until it has had time to
cool.
20. =_Don’t_= forget daily to see that the safety-valve moves freely
and is tight.
21. =_Don’t_= fail to clean the boiler inside frequently and
carefully.