HOTPRO Woodfired Water Heaters all utilize a 4" chimney. For indoor installations, the connection between the water heater and the ceiling or wall connection is made with 4" single wall all-fuel stove pipe.
This is available as the HOTPRO Chimney Kit(see page 19) or is commonly available as 4" snap-together blue single wall pipe. This is available at most hardware or stove stores.
When single wall chimney is used, clearance from combustibles to the pipe is a minimum of 18", or adequate shielding must be used. Double wall all-fuel chimney is also available for closer clearances.
Whenever the chimney goes through a wall or ceiling, triple wall Class A all-fuel chimney is used.
For outdoor installations, a run of 24"or more of single wall chimney is adequate.

Every HOTPRO Woodfired Water Heater comes with a Watts Regulator 100 XL Automatic-Reseating Combination Type Temperature and Pressure Relief Valve installed.
The valve opens if pressure exceeds 125 PSI or the temperature exceeds 210ºF.
As part of your installation, the T & P Valve must be connected to a valve outlet and run to a safe place of disposal.
The T & P Valve box is included in the component box of each HOTPRO Woodfired Water Heater. Carefully follow the Watts Reg. Co. instructions on how to plumb the discharge line.
Never remove the T & P Valve from your water heater. It is required for safe operation of the water heater.