bing tracking image
  1. Accessories and Parts
  2. Demco
  3. Tow Bar Braking Systems
  4. Hardware
Replacement Check Valve for Demco SBS Supplemental Braking Systems

Replacement Check Valve for Demco SBS Supplemental Braking Systems

Item # SM99909
Our Price: $16.04
You Save: 12%
Accessories and Parts

Will this fit?

To see if this custom-fit item will work for you please tell us what vehicle you'll use it with.

Orders above $50 qualify for Free Shipping
Shipping Weight: 0.01 lbs
In Stock
zoom in icon
slider vertical icon
zoom out icon
Comment field cannot be left empty.
Name field cannot be left empty.

Thank you! Your comment has been submitted successfully. You should be able to view your question/comment here within a few days.

Error submitting comment. Please try again momentarily.

Product Images

In Use/Installed

Need help with installation?
Locate installers near me
Replaces the check valve that came with your Demco SBS Air Force One (SM99202 or SM99243) or Stay-IN-Play Duo supplemental braking system (SM99251). 1-833-496-1390 to order Demco accessories and parts part number SM99909 or order online at Free expert support on all Demco products. Great prices and Fastest Shipping for Replacement Check Valve for Demco SBS Supplemental Braking Systems. Accessories and Parts reviews from real customers.
  • All Info
  • Reviews (27)
  • Q & A (0)
  • Videos (2)
  • Photos
  • Why etrailer?

Demco Accessories and Parts - SM99909

  • Tow Bar Braking Systems
  • Hardware
  • Demco

Replaces the check valve that came with your Demco SBS Air Force One (SM99202 or SM99243) or Stay-IN-Play Duo supplemental braking system (SM99251).


  • Replaces the check valve that came with your Demco SBS supplemental braking system
    • Works with Air Force One (SM99202 or SM99243) and Stay-IN-Play Duo (SM99251)
  • Check valve installs between the brake booster and the towed car's engine
  • Required on all towed cars that don't have a diesel engine and aren't Hummers
  • Includes 1 replacement check valve

16126 Demco SBS - (Formerly SMI) Replacement Check Valve for Air Force One or Stay-IN-Play Duo Supplemental Proportional Braking System

Replaces Demco SBS SM15601 and SM99909

Video of Replacement Check Valve for Demco SBS Supplemental Braking Systems

Videos are provided as a guide only. Refer to manufacturer installation instructions and specs for complete information.

Video Transcript for Demco SBS Replacement Check Valve Review

Hello neighbors, it's Brad here at etrailer, and today we're taking a look at a replacement one-way check valve for your Demco Stay-IN-Play DUO Supplemental Braking System. Now this is gonna work on either system, if you have the Stay-IN-Play DUO with the wired LED, or the one with the wireless coachlink, it's gonna work all the same. And this is just the pneumatic part when you tie into the brake master cylinder line. So in the vacuum system, when you tie into it with the T, you do have to put a one-way check valve in line with that, and that's gonna make sure that you're not pulling air from the crankcase, that can really only allow air one way, hence the name one-way check valve. But if this was to fail, this isn't gonna close that flap, and it's not gonna be able to pull suction into the compressor, therefore, your cylinder is not gonna work and your brakes will not be working. So if your brake cylinder is not actually working when you're applying the brakes on the vehicle, it could be a number of things, the main thing you're gonna wanna check right away is that the actual compressor is kicking on.

And if it is, and it's acting as normal but you still don't have that brake pressure, it's very possible it's gonna be that check valve. Now you can check these pretty easily just by a manual check, kinda just by blowing through and creating suction. And the way that it works is it allows air to go one way, but when it actually goes the other way, so like a suction, that flap closes, not allowing that air to go anywhere. So that flap is just kind of a small little rubber. Over time, once it kind of moves and moves and moves, it does wear down and it can become brittle, therefore creating a leak of air.

So a quick little check. I can blow through, great. Suctioning it in, I couldn't pull any air through, so this one is good. If yours is broken down, then you might be able to still pull some air through that, and that's gonna be a problem when you're trying to brake. Now, you do have 2 one-way check valves, the one here is actually installed off of the compressor, and then you'll put the one in line here.

The black and the clear/green as they call it in the instruction manual, does denote which way that it needs to face, and you will need to keep these according to how they we're installed the previous time. So that way, you're not pulling from the crankcase, or you're not also pulling anything in here or pushing out, so we're gonna keep that air flowing the proper way. So easy way to get these out, you can actually make a small slit here with a razor knife. They can be a little bit tricky once they kind of bind onto this teeth, so if you need to, you can actually use a pick, pry that out, little silicone also helps pull this off as well. But once you have that off, you can simply pop the new one in place.

Also, you can use a little silicone to put it back in, and then once you put those hoses back together, your installation of your replacement check valve is complete. Now, if you do have to slit this back to get this off, I do recommend going back and cutting it with a airline cutter, we have those available here at etrailer, and that's just gonna make a nice clean cut. And during the installation of our braking system, I try to leave just a little bit of extra, that way if you do ever have to replace anything, you can still have enough hose to make that attachment point. And that was a look at the replacement one-way check valve for your Stay-IN-Play DUO Supplemental Braking System..

Customer Satisfaction Score:

Customer Reviews

Replacement Check Valve for Demco SBS Supplemental Braking Systems - SM99909

Average Customer Rating:  4.9 out of 5 stars   (27 Customer Reviews)

Replaces the check valve that came with your Demco SBS Air Force One (SM99202 or SM99243) or Stay-IN-Play Duo supplemental braking system (SM99251).


Check valve was delivered promptly and fixed the problem I had with the old one.


Needed a check valve to install a braking device on Jeep when towing behind a Class C. Finding the part on the website was a bit challenging but, they had it. Ordering was simple and straightforward.


Worked perfectly in my application.

Still working flawlessly
James - 05/07/2022


Very prompt service and exactly what we needed.


Executed as promised


The part came quickly and was the correct part. I am very pleased with etrailer and will use them again.


Great communications and fast delivery.


Ordered this to have on hand in case it is needed. We had one go out on us & the manufacture replaced it under warranty. it is an easy fix if you have the part.


Exactly what I needed. Bought a used Invisi-Brake and needed a 3/8 check valve for the master cylinder. This part is perfect. Fast shipping and a great price!!


Worked perfectly in my application


etrailer does a very good job for us in all areas


replaced a bad check valve after five y ears.


Came quickly and well priced

Patrick C - 04/10/2020


Fast, as ordered, pleasure to do business with.


This product is exactly what I was looking for . Works as advertised. Prompt shipment



As advertised.


Inexpensive item that should be replaced yearly for safety reasons.








Show More Reviews

See what our Experts say about this Demco Accessories and Parts

  • Troubleshooting SMI Air Force One Braking System Triggering Check Engine Light on Toyota Corolla
    I reached out to my contact at SMI (now Demco) and he said that on your 2017 Toyota Corolla iM the exhaust port on the Air Force One # SM99243 operating unit does need to be left open. He said the issue in your case is that the vacuum check valve between the tee and operating unit has likely failed. You can simply replace this vacuum check valve with part # SM99909 and face the black portion of the valve towards the unit, making sure to unplug the exhaust port in the process. This should...
    view full answer...
  • Is The Check Valve For Demco SBS Braking System Necessary.
    The Replacement Check Valve for Demco SBS Supplemental Braking Systems # SM99909 required for all towed vehicles that don't have a diesel engine and are not Hummers. A vacuum pump check valve for automobiles, also known as a vacuum check valve, is a part of your car that's responsible for making your vacuum pump system work. This valve seals and holds the vacuum flow up for energy-efficient and completely safe operation. You need it, for example, for your vehicle to brake properly.
    view full answer...
  • Replacement Cap for Demco Air Force One Supplemental Braking System
    It sounds like you are looking for the Vinyl Cap for Demco SBS Air Force One Supplemental Braking System # SM99608.
    view full answer...
  • Installation of SMI Replacement Check Valve on 2019 Ford Ranger
    The Replacement Check Valve for SMI Supplemental Braking Systems # SM99909 on your 2019 Ford Ranger will install in the either of those two hoses according to my tech contact at Demco (who owns SMI). He said you will install it only in whichever line you install the T-Fitting. The rubber hose will be easier for sure so that is my recommendation and the black side of the check valve needs to be on the engine side. I've attached a photo from the instruction manual of the SMI Stay-IN-Play...
    view full answer...
    Image 1 for Image 2 for
  • Check Valve for SMI Supplemental Braking System on 2003 Jaguar X-Type
    The Replacement Check Valve # SM99909 that you referenced is designed for use with the SMI Stay-IN-Play DUO Braking System # SM99251 or the Air Force One # SM99243 and is needed on your Jaguar if you are installing either of these systems. The valve will indeed fit your vehicle. I have attached a couple diagrams taken from the installation instructions for these braking systems that you can take a look at as well.
    view full answer...
    Image 1 for Image 2 for
  • Recommended Replacement Components for SMI Air Force One on 2019 Ford Ranger
    You can use the 1/4" Air Line Hose - SMI Air Force One or Stay-In-Play Duo Supplemental Braking System # DM16114 sold in 1 foot increments, so if you need 6 feet of new hose you can simply select quantity 6 on that product page and you will receive one 6 foot section of hose. The compression fittings like the Replacement Female Push-On Hose Connector for SMI Air Force One Supplemental Braking System # SM99726, the Replacement 1/4" Female Pushlock Fitting for SMI Supplemental Braking...
    view full answer...
  • Demco SBS Air Force One Replacement Parts for Poor Vacuum on 2018 Jeep JK Rubicon
    The Demco SBS Air Pressure Stop Light Switch Kit for Towed Vehicles - Air Force One # SM99629 will have that fitting you are referencing. You will also want to check any fittings like the Replacement 1/4" Female Pushlock Fitting for Demco SBS Supplemental Braking Systems - Qty 1 # SM99611 or check valves # SM99909. If the controller is the issue then you will need the Demco SBS Second Vehicle Kit for Air Force One Supplemental Braking System # SM99209. The controller is not available...
    view full answer...
  • What are the Dimensions of SMI replacement Check Valve # SM99909
    I measured the Replacement Check Valve for SMI Supplemental Braking Systems # SM99909 for you. The overall diameter at the barbs for each end is 0.42 inches. The more narrow parts at the base have a diameter of 0.37 inches. The center, widest section is 0.76 inches in diameter. The overall length is 1.66 inches. This valve was designed to work with the Air Force One SM99202 or # SM99243 and Stay-IN-Play Duo # SM99251. So if you have one of these systems this is the correct replacement. If...
    view full answer...
    Image 1 for

Do you have a question about this Accessories and Part?

  • Why

    At we guarantee:
  • Real product know-how.

    We make sure that the products we sell are what we say they are, and that they work the way they are supposed to work. Get real advice from a real person who has the knowledge and expertise needed to solve your problem.
  • Most detailed, accurate accessories and part information available.

    Because we take providing accurate product information seriously, we take our own detailed product photos, demo videos and installation videos, as well as verify measurements, instructions, and vehicle fit information.
  • Installations, made easy.

    We love helping people and have the most highly-trained customer service, hands-on experience, step by step videos and installation instructions.
  • Fast shipping.

    Your order is automatically routed to get out of our warehouse and to your door as quickly as possible. Receive free shipping on orders over $99.
  • Personalized service for life.

    We provide one-on-one, personalized service from the ordering process through the life of your product.
  • Trusted since 1946.

    We've been serving customers since our parts store first opened in 1946 and continue to be recognized by our customers, our vendors and third parties for exceptional service.
  • Returns Policy

    Need to return an item? No problem. Please read our Returns Policy for more information.

Info for this part was:

Employee Michael H
Expert Research:
Michael H
Employee Jameson C
Expert Research:
Jameson C
Employee Jacob T
Video Edited:
Jacob T
Employee Dustin K
Video by:
Dustin K
Employee Wilson B
Written by:
Wilson B
Employee Kristina F
Updated by:
Kristina F
Employee Michael B
Installed by:
Michael B
Employee Bradley B
Installed by:
Bradley B

At we provide the best information available about the products we sell. We take the quality of our information seriously so that you can get the right part the first time. Let us know if anything is missing or if you have any questions.

Product Experts Available Now!
Call 1-833-496-1390