It is recommended that all couplings be regularly cleaned and lubricated with grease in order to prevent leakages or damage to gaskets

It is important that system nozzles are always fitted in couplings on guns/valves, or otherwise the O-rings will be flushed out, or water behind them will make the system nozzles very difficult to install.

If you need to replace the O-rings, here is a video guide to how it is done.