Checking for bad or leaky valve seals is an easy way to conserve the gas flowing through the pipes, make a system run more efficiently and prevent dangerous buildups to gas in small areas. A simple seal leak detector consists of soapy water.
Prepare a solution of soap and water. Use liquid dishwashing soap and regular tap water, at least 25 percent soap to 75 percent water. More soap won't hurt the solution and may allow the detection of smaller leaks, but 25 percent should be enough.
Remove any impediments to physical access to the valve.
Ensure that the entire valve seal is visible.
Apply soap and water solution to the entire length of the seal. Use either a thoroughly wet sponge, rag or a spray bottle. Set on stream, the mist setting won't get enough water on the seal to completely wet the seal.
Check the entire seal for bubbles. If there is an area where bubbles grow quickly, this indicates a leak.