A.O. Smith GP 6 40YPC T 100 User Manual

52

23. Turn on the gas supply to the unit and test the gas 

supply line and union connections by brushing on 

an approved noncorrosive leak detection solution 

(Figure 116).

24. Turn on the electrical and the gas supplies to the 

water heater. Plug in the electric connection from 

the transformer to the electric outlet (Figure 113).

25. Restart the water heater by following the 

directions on the “Lighting and Operating 

Instructions” label located on the front of the water 

heater .

26. As the burner is heating (view flames through 

viewport), test the manifold tube connection at 

the gas control valve/thermostat by brushing on 

an approved noncorrosive leak detection solution 

(IMPORTANT: Do Not splash any solution onto 

any electrical connections) (Figure 120).

27. Upon verifying proper operation of the water 

heater, replace the manifold cover/outer door.

Gas  pressure  checks  are  done  with  flowing  gas                  

using a gas pressure gauge capable of reading 

pressure in inches of water column. 

supply gas pressure is under desired pressure 
requirement

• 

increase supply gas pressure regulator setting 

and,

• 

increase supply gas piping size.

supply gas pressure is over desired pressure

• 

add gas pressure regulator.

• 

reduce setting on existing regulator.

manifold gas pressure is more than +/- .3 inch 
W.C. from values indicated on gas valve

• 

ensure there is adequate supply gas pressure

• 

ensure the main burner orifi ce is the correct size 
for the water heater model being tested.

• 

if the above tests have been performed and the 
results were correct replace the gas control valve.

•

•

Supply gas pressure checks are measured 
before the gas control valve/thermostat and 
as close to the water heater as possible.

Manifold (main burner) gas pressure is 
measured at the pressure tap on the side 
of the gas control valve/thermostat. Use 
an allen wrench to remove the plug then 
attach the gas gauge.

NOTE: Desired gas pressures will be noted on 

the gas valve label located on the gas control 

valve/thermostat.