Can I Install the Demco Coach Air Kit Without Cutting the Factory Air Lines?

Updated 09/02/2026 | Published 08/27/2026

Question:

Hello, I have watched installation videos for this product and am considering doing the installation slightly different. Instead of cutting the factory air lines, I would rather leave them intact in the case that the additional parts may need to be removed at some point in the future. I would do so by disconnecting the air line at the relay valve, attaching the tee, and adding a short length of air line between the tee and the valve. In the case of the source air, I may consider connecting directly to the coach air tank if a spare port is available to avoid using a tee at all. I understand that this will increase the cost of the install in order to source the additional air line required. Have you done installations this way? Do you see any issues doing the install this way? Do you have a recommended source for the air line required to support such an installation? I value your experience and expertise and greatly appreciate your advice. Thank you.

asked by: Steve B

Expert Reply:

Hello Steve,

Thanks for writing in.

I completely understand what you are wanting to do, especially if you want the option to return everything back to factory later on.

With the Demco Coach Air Kit # SM99627, I would recommend sticking with Demco’s installation instructions and using the tees at the specified air lines. Your idea makes sense, but since it would be different from how Demco designed and tested the system to be installed, I cannot recommend going that route. Not fully following the manufacturer’s installation instructions could also void the warranty.

I know cutting into the factory air lines is not always ideal, but with something tied into the coach’s braking system, I would definitely stick with Demco’s approved installation.

What kind of motorhome are you getting set up to flat tow with?

expert reply by: Kate F

Steve B.

9/1/2026

I will be towing with a 2024 Newmar Superstar motorhome.

Kate F.

9/2/2026

@SteveB Wow, that is a really nice camper! House on wheels =) - Safe Travels

Tim M.

9/2/2026

Hello, I installed this kit in our Renegade Verona LE (same chassis as your Super Star). The biggest thing to make sure of is that you have the correct lines above the axle. I almost cut the wrong line, but got on the phone with Demco and their customer service was very helpful. All of my air lines were coated with black paint and were difficult to identify. The Freightliner color coding does not match the Demco instructions. The other trick is to sit up behind the axle and reach over it to detach the air line at the relay valve. I was initially trying to do it laying on a creeper under the coach and it was too far away to reach. Once I figured out there was enough room to sit upright on the creeper, everything was within easy reach. Your idea of using an extension rather than cutting the factory line is a good one. I would not connect the supply directly to the tank, just tee into an existing line is easier. There's also a separate tee you have to buy as the M2 chassis has a different air line diameter than the class A chassis. I can't recall the details, I think it's 5/8" vs. 1/2, but I could be wrong about that...

Bob R.

9/2/2026

I agree with other comments discouraging what you suggest. I did both sides (Jeep and 45’ RV) of the install myself. It took some time as I wanted to be sure of each step… but I would not depart from the recommended procedures as it could void all warranties and might not be safe. Also, it’s a simple fix for anybody to remove the T and replace with a pass thru. The only thing I will stress is the small tank placement on the RV is very important, as most coaches with airbags change their footprint with bags full versus empty.