3” Diameter Venting Overview (Bosch 250SX/635ES)

Not sure what you need?  This venting overview provides our recommendations broken out by vertical (thru the roof) and horizontal (thru the wall) installations.

Recommendations when venting through the roof (vertical):

1. Condensate Drain Kit – The condensate drain kit is made for the Bosch 250SX/635ES only. To be used for all vertical installations.  The condensate tube is made of silicon to prevent corrosion and should be filled with water to prevent gases from coming out of the tubing. The tubing should be fed into either a drain or a collection bucket through some form of piping or tubing although the amount of water that will come through the condensate drain is limited.  

2. Vent Piping – available in lengths of 6 inches to 4 feet.

3. Fire Stop Support – for use when the vent piping passes through a floor.  

4. Roof Flashing – for use where the vent piping passes through the roof.  Available in 2 slope ranges:

   • Roof Flashing 0/12-6/12  

   • Steep Roof Flashing 7/12-12/12  

5. Storm collar – sits on top of the roof flashing to make a weather seal with the roof flashing.

6. Rain Cap – stainless steel rain cap  

7. If drawing air through inlet venting the following products are suggested:

   • Vent Hood w 4" sleeve  

   • 10 ft Roll Intake Vent Hose – PVC or any aluminum flex tubing can be substituted.

8. Optional accessories:

   • Isolator EXP Tankless Water Heater Service Valve - a complete inlet/outlet valve system that provides for a secure tankless installation including full port testing and flushing of the system with easy to install union connections and easy two step installation.

   • Wireless Remote Control for Bosch 250SX – to adjust the output water temperature remotely.  Note the Bosch 250SX has a digital display on the water heater which can perform the same functions.  

Recommendations when venting through the wall (horizontal):

1. AQ3 Horizontal Vent Kit - includes the vent parts for a 10 ft vent intake and the venting to exhaust directly out a wall with no horizontal run. 

Kit includes:

• One Adjustable Adapter(11.5” to 15”),

• One 90 degree elbow(3")

• One 3” wall thimble

• One 3” exhaust vent hood with 4” sleeve

• One 3" x 1' section of vent pipe

• One 3” X 10’ aluminum flex pipe (for inlet air)

• Two 3” intake vent hood w/4” sleeve

• Two 3” gear clamps

• Note:  Additional vent piping must also be purchased if you will have a horizontal run

2. Condensate Drain Kit (not needed if vent piping length is less than 5 feet)  – The condensate drain kit is made for the Bosch 250SX/635ES. To be used for horizontal installations that are greater than 5 feet in total length in any direction.  The condensate tube is made of silicon to prevent corrosion and should be filled with water to prevent gases from coming out of the tubing. The tubing should be fed into either a drain or a collection bucket through some form of piping or tubing although the amount of water that will come through the condensate drain is limited.

3. Vent Piping – available in lengths of 6 inches to 4 feet.

Individual Horizontal Venting Components (if not purchasing AQ3 vent kit or need additional vent pieces):

1. Wall Thimble - The wall thimble is used for horizontal exhaust venting through the outside wall.

2. Adjustable Adapter - The adjustable adapter simplifies the installation since the pipe can be adjusted from 11.5 inches to 15 inches in length.

3. Elbows – available in 45 degrees and 90 degrees:  

   • 45 degree elbow

   • 90 degree elbow

4. Vent Hood w 4" sleeve - for use as intake or exhaust vent hood.

5. If drawing air through inlet venting the following products are suggested:  

   • Vent Hood w 4” sleeve

   • 10 ft Roll Intake Vent Hose – PVC or any aluminum flex tubing can be substituted.

6. Optional accessories:  

   • Isolator EXP Tankless Water Heater Service Valve - a complete inlet/outlet valve system that provides for a secure tankless installation including full port testing and flushing of the system with easy to install union connections and easy two step installation.

7. Wireless Remote Control for Bosch 250SX – to adjust the output water temperature remotely.  Note the Bosch 250SX has a digital display on the water heater which can perform the same functions.

Buying Guide For Tankless Water Heaters

• How does a tankless water heater work?
• What factors to consider when purchasing a tankless water heater?
• What factors to consider when purchasing a gas tankless unit?
• What factors to consider when purchasing an electric tankless water heater?
• Online tankless water heater consultant - helping you select the right unit