Shut Off Valves
There are 3 shut off valves required for an integrated combo system as follows:
•One valve (a) on the cold water side of the water heater upstream of the heating loop connection. This valve has the ability to isolate the hot water (domestic and space heating) from the household cold water supply. This valve is required on every water heater whether or not the water heater is used for space heating.
•One valve (b) on the hot water supply side of the heating loop, downstream of its connection to the domestic water.
•One valve (c) on the return side of the heating loop upstream of its connection to the domestic cold water.
The two valves in the heating loop allow the heating loop to be isolated for service or repair.
(a) 
Supply
(b)
(c) Return
H C
SHUT OFF VALVES
Drain Valve
system. The drain valve should be near the low point of the return piping system upstream of the shut off valve and is preferred to be near the water heater.
Throttling Valve
The throttling (balancing) valve is used to reduce the water flow rate and thereby increase the water temperature drop. This is done to ensure proper activation of the water heater thermostat. This valve should be a globe or balancing valve.
Check Valves
A spring loaded check valve is required in the heating loop to help minimize
CHECK VALVE
A drain valve is required to allow the heating loop to be drained for service or repair and to remove air from the heating loop when commissioning a
*Check valves should always be installed in a vertical rise with the flow of water shown.
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