Valve fittings

Two kinds of valve built into a fitting. The check valve lets air pass one way only and holds a cylinder under pressure if the supply drops out. The stop fitting closes itself the moment you pull the tube out.That last one saves blowing down the whole system for a single repair. Watch the flow direction: it is marked on the body and only goes in one way round. Fitted backwards, a check valve does nothing at all, right up until you need it.