Are you a mechanic, distributor or B2B buyer and you want to purchase heater hoses in bulk for your automotive business? If yes, then your biggest challenge is selecting the right hose size and specifications for your use.
That is why we wrote this topic for you. We will cover common heater hose sizes and their suitable applications. Our team also shared useful tips on how you can check the exact size of hose.
Standard Heater Hose Sizes Data
Most automotive and industrial heater hoses follow SAE J20 20R3 guidelines. The exact outside diameter, wall thickness or pressure rating can change based on the hose material such as silicone rubber or reinforced EPDM. The values below show common industry ranges for heater conduits.
| ID (inches) | ID (mm) | OD (mm) | Wall Thickness | Operating Pressure | Burst Pressure | Application |
| 1/4 inch | 6 mm | 13 mm | 3 mm | 60 to 75 psi | 20 to 300 psi | Small engines & vacuum lines |
| 5/16 inch | 8 mm | 14 mm | 3 mm | 60 to 75 psi | 250 – 300 psi | Small heater connections & coolant bypass lines |
| 11/32 inch | 9 mm | 15 mm | 3 mm | 60 – 75 psi | 250 to 300 psi | Small heater and coolant connections |
| 3/8 inches | 10 mm | 17 mm | 4 mm | 60 to 75 psi | 250 to 300 psi | Small cars & light-duty vehicles |
| 1/2 inch | 13 mm | 20 mm | 4 mm | 50 – 65 psi | 200 to 250 psi | Cars, SUVs, some light trucks |
| 5/8 inch | 16 mm | 24 mm | 4 mm | 50 to 65 psi | 200 to 250 psi | Passenger cars, SUVs, vans & trucks |
| 11/16 inch | 17 mm | 25 mm | 4 mm | 50 – 65 psi | 200 to 250 psi | Cars, SUVs, light trucks |
| 3/4 inch | 19 mm | 28 mm | 4 mm | 45 to 60 psi | 175 – 225 psi | Truck, commercial HVAC, main heater return lines |
| 7/8 inch | 22 mm | 31 mm | 4 mm | 40 to 50 psi | 160 – 200 psi | Machinery/agricultural equipment coolant loops |
| 1 inch | 25 mm | 35 mm | 5 mm | 40 to 50 psi | 150 to 175 psi | Industrial heater supply lines |
| 1-1/4 inch | 32 mm | 41 mm | 5 mm | 30 to 45 psi | 125 to 150 psi | Buses, RVs, or industrial vehicles |
| 1-1/2 inch | 38 mm | 48 mm | 5 mm | 25 to 40 psi | 100 to 125 psi | Lower/upper coolant connections |
Note: Standard EPDM heater tubes can handle temperatures between -40°F to 257°F (-40°C to 125°C). In contrast, silicone heater hoses can manage a wider temperature range around -65°F to 350°F (-54°C to 177°C). Moreover, these tubes have thicker walls and higher pressure ratings (80+ PSI) as compared to standard EPDM rubber hoses.
Definition of Heater Hose Dimensions
ID Heater Hose: The inside diameter (ID) of heater pipe is the straight distance across the inner wall of the hose to the opposite inner wall. ID is mostly mentioned in inches, like 3/4-inch, 3/4″, 0.75″ or in millimeters such as 19 mm.
OD of Heater Hose: The outer diameter, or OD, measures the full width of the hose from one outside edge to the other. You can use the OD to check if the hose will fit in the available space or choose hose clamp/fitting.
Wall Thickness: Wall thickness is the distance between the inside wall and outside wall of the heater hose. It basically shows you the thickness of hose material. Manufacturers mostly measure it in millimeters (mm). A thicker wall can give the hose more strength, so it can handle heat/pressure.
Operating Pressure: This tells you the amount of internal pressure the hose can handle during normal vehicle operation without losing its shape or sealing ability. You will see this rating in PSI or bar.
Bursting Pressure: This is the maximum limit of pressure level at which the hose can rupture. It gives you an idea of the hose’s pressure limit under extreme conditions. In short, burst pressure rating is a safety margin above the normal working pressure.
Heater Hose DN Size Conversion
What is nominal diameter of pipe? DN means Nominal Diameter. It is the standard name or size assigned to a heater hose based on its approximate internal diameter. It gives you a simple way to identify and compare pipe sizes without the use of exact inside or outside measurements.
| DN Size (Nominal Hose Diameter) | Heater Hose Size (Inch) | Inside Diameter (mm) |
| DN6 | 1/4″ | 6.3 mm |
| DN8 | 5/16″ | 7.9 mm |
| DN10 | 3/8″ | 9.5 mm |
| DN13 | 1/2″ | 12.7 mm |
| DN16 | 5/8″ | 15.8 mm |
| DN18 | 11/16″ | 17.5 mm |
| DN20 | 3/4″ | 19.0 mm |
| DN22 | 7/8″ | 22.2 mm |
| DN25 | 1″ | 25.4 mm |
| DN32 | 1 to 1/4″ | 31.8 mm |
| DN40 | 1 to 1/2″ | 38.1 mm |
Reminder: Keep in mind that DN is a nominal size. It means it is not an exact measurement. For example: industrial gloves marked “Small”, “Medium” or “Large” give you a size name. But it does not tell you the actual measurement of the glove. DN works in a similar way for pipes and hoses. So if you want to order a heater tube for your car, we advise you to check the actual inside diameter of the hose and the fitting before you choose the replacement.
How Can You Identify Correct Heater Hose Size For Your Car?
You need a correct heater hose size to get a proper fit and prevent coolant leaks in your vehicle. For this purpose, you have to identify the right size of hose. But the question is, how to measure a heater hose? Well, you only need to follow these simple steps to check the dimensions of the heater conduit and select the perfect one for your automobile.
- Check your vehicle manual: You should always look for the heater hose size listed for your car model and engine.
- Measure old hose: You can use a ruler or caliper to measure the inside diameter (ID) of the old heater tube in your car. This gives you the most useful size to find a perfect replacement.
- Check connection: It’s also important to measure the outside diameter of the heater core or engine fitting. Then you can match hose ID with fitting size.
- Hose marking: Sometimes, hoses have their size printed on the outer surface. For example, a marking such as “5/8 IN” tells you that the pipe has a 5/8-inch nominal ID.
- Compare the hose length: We also recommend that you make sure the replacement hose has enough length. So that the tube can follow the same route without sharp bends or excessive stretching.
- Match hose type: Always choose a heater conduit that can handle your vehicle’s coolant, temperature, as well as pressure requirements.
Example: Heater hose sizes for 1 inch water pump nipple
What Happens If You Use Wrong Heater Hose Size?
In case you install a heater hose in your car that does not match the fitting correctly, it will lead to several problems and some listed below.
- Coolant leaks
- Loose hose connections
- Restricted coolant flow
- Poor cabin heating
- Hose blow-off
- Engine overheating
- Premature hose damage
- Air can enter cooling system
RONTEIX Custom Heater Hoses
RONTEIX is a manufacturer and supplier of automobile hoses including coolant hoses. With over 18 years of manufacturing experience, we specialize in custom heater hoses for automotive and heavy-duty applications. We offer OEM and ODM services for wholesalers and distributors worldwide.
So you can request custom heater tube sizes, shapes, thicknesses and reinforcement layers based on your requirements. Talk to our team today and share your details to get a customized solution and factory direct quote.
Wrapping It Up
As you can see, heater hoses are available in many sizes. However, 1/2 inch, 5/8 inch and 3/4 inch are among the most popular dimensions. If you need hoses for different vehicle models, then you should definitely consider custom heater hoses.
Before you place a bulk order, we recommend you to request a sample from your supplier first. Because you can check the actual size and performance of heater hoses before you invest in a large quantity.
