Do you need any lubricant or other maintenance for a QEV?

[urbanfarm]

So does a QEV require a maintenance dose of lubricant?

Next, what would one lubricate a QEV with?

And finally the little diaphragm/piston is that replaceable?

[psycix]

A QEV does not need lubricant or maintanaince.
Though if you think there is stuff inside it (for example if you fired flour or confetti with your gun) and it does not seal anymore you can always open it up to clean stuff.

The piston is replaceable. Depends on brand but spare pistons should be available for just a few bucks.

[Hotwired]

I don't think I've seen replacement pistons anywhere. You might need to contact the manufacturer or even be expected to buy a new valve (not a good thing for large valves).

[Daltonultra]

If you need a replacement piston, use a hockey puck. Slice it in half, then cut it to fit the chamber.