Originally Posted by tgmillso
I did both simultaneously at first. The balloon burst at .5 psi. A Balloon is simply not a reliable measurement device. Van's indicates that 1psi should be your target test value. Just don't over pressure it, so cut the hose off or bend it over at this point so you can't. I then just used the manometer and took it to 27in of head. I used some clear plastic 3/8" hose I bought at the hardware store, flared the end and used an 818 nut and 819 sleeve to attach it to the tank. You should have plenty of these in your bag of fuel fittings. It really isn't that complicated, but it is accurate.
The instructions I have (came with the vans test kit) refer to the maximum pressure in the tank during operation being "very low, less than 1 PSI".
The manometer is then offered as an alternative to the balloon. "When the water level in the open end of the tube is 27" higher than the level in the end attached to the vent, you will have 1 psi in the tank". I do not read this as you MUST have 1psi, but rather that this is your limit. Again, the soapy water test is still specified as the method for detecting leaks.
IMO 1 PSI should be a LIMIT and not a TARGET, any positive pressure will show up leaks under the soapy water test, it doesn't need to be exact.