Tech 101: The Hows and Whys of Installing a Tanks Inc. Rollover Vent Valve

Tanks Inc. is a leader in fuel tanks.

The company has been in business since 1980, but aftermarket fuel system component manufacturers like Edelbrock and Aeromotive are now recommending Tanks Inc. fuel tanks for use with its fuel systems. Tanks Inc. also offers a variety of complementary parts to work with its gas tanks, including a remote-mount rollover vent valve.

While researching fuel system components for another project, we noticed a lot of questions about the use and installation of rollover vent valves on various forums. So we decided to reach out to Tanks Inc. to find answers.

“Why do you need a rollover vent valve in the first place?”

Rollover vent valves perform two essential functions. Used in conjunction with your vent line, a rollover valve will allow your tank to breathe and not build up pressure or vacuum during normal operation. Remember, as fuel is added to your tank, air in the tank is displaced and has to go somewhere. Vent lines and vent valves allow air to be released so pressure doesn’t build. Likewise, as fuel is drawn from the tank, the vent lines and valves allow air to return to the tank so a vacuum situation is avoided. The second function of the rollover vent valve (and what separates it from regular vent valves and lines) is to prevent gas from running out of your vent line during an accident. When the rollover vent valve is on its side or upside down, a check ball inside the valve will close to prevent gas from running out.

“What’s the difference between a remote-mount rollover valve, like the Tanks Inc. rollover valve, and an in-tank rollover valve?”

An in-tank valve performs the same function as its remote-mount counterpart, preventing fuel from draining out through your vent line during accidents. However, a remote-mount rollover valve can be used in cases where there is no room to install an in-tank valve.

“Are there any special features you should look for in rollover valve?”

According to Justin Somerville, general manager at Tanks Inc., most vent valves are created equal, except for one important feature. “Our remote rollover vent valve also comes with a screen to help keep contaminates out of your vent line and tank,” Somerville said. “This is a feature that is not common on most vent valves.”

“What’s the best way to install a remote-mount rollover vent valve?”

Somerville says he sees three common mounting mistakes that should be avoided when installing a remote-mount rollover valve.

1. Mounting the valve too low. “Your vent line should be the highest point on your tank system,” he said. “This means that the vent must be higher than the highest point on tank including the fuel filler neck.”
2. Mounting the valve at an angle or horizontally. “Mounting the vent valve on its side or upside down will cause the vent to always be shut and your tank will not be properly vented,” Somerville said. “Make sure that the vent valve is mounted vertically. In the case of our remote rollover vent this means that the hose barb should be facing down with the aluminum cylinder sitting on top.”
3. Creating a trap within the vent line between the tank and vent valve. “When routing the vent line from the tank to the vent valve you must avoid running the vent line down and then back up again,” Somerville said. “Like a P-trap under a sink, this is a place that condensation or fuel can become trapped in the line. This trap will then block off your vent line and your tank will build pressure or vacuum until there is enough pressure to purge the vent which will cause gas and/or odor to come from the vent line.”

“Is there anything that can be done about fumes coming from the valve?”

When a rollover vent valve (or any vent line or valve, for that matter) is working properly, it acts simply as an open-air vent. Unfortunately, that means gas fumes will escape.

One of the most common questions centered around what can be done about these fumes.

“Fumes can be minimized by having the vent line ran as high as possible,” Somerville said. “Making sure that a P-trap is not created will make sure that the pressure in your tank doesn’t build until your tank burps and purges the vent line. This sudden burp can fill your garage with gas odor.”

The only way to completely eliminate fumes is to install a vapor recovery system, like ones found in a late-model car. This is a fairly involved setup that includes a charcoal canister with vacuum lines running between the canister and engine, where the vacuum will pull the fumes into the intake of the engine.

Some people try to use only the charcoal canister to reduce fumes, but this typically is not a permanent fix because the filter will become saturated eventually and ineffective without the vacuum lines. According to Somerville, II Much Fabrication offers a solution that eliminates most odors without vacuum lines. This odor-reducing vent valve can be installed in tandem with the Tanks rollover valve to create a fume-reducing, remote-mount option.

“The top cylinder of our remote mounted rollover vent valve can be removed as the rollover check ball is in the hose barb itself,” Somerville said. “The top of the remote rollover vent valve is male ¼-inch NPT thread so you can hook it into a vent system if you choose.”

Fumes or no fumes, a properly mounted vent valve will keep you safe and help your fuel system operating efficiently.