[Richard L]

There are two types of dribble.

1. Line decompression:
A checkvalve will not stop this totally but helps to minimise it. There are two kinds of wmi systems, PWM valve (aquamist) and PWM pump (the rest). there is minimum dribble with aquamist because the line de-pressurise period is relatively short (milli-seconds rather than seconds) due to the sharp cutoff action of the inline valve. Using a small OD hose (4mm) has help greatly.

2. Siphoning effect between multiple jets:
During injection, every line to the jets are filled with fluid. Upon shutting off, the line fluid will be drawn out by delta pressure between jets. If you use multiple checkvalve, this siphoning effect is almost eliminated due the the delta pressure is blocked off by the action of the checkvalve.

Conclusion:
Checkvalve is important if you are using multiple jets especially when there are vacuums. We have heard quite a few extreme cases with manifold got blown apart. But this is rare. The amr (air/meth/ratio) has to be pretty close to 6.6: 1 for an explosion to happen.

Describe your current set up to me here.