What good is a Master Valve in an irrigation system???? Most companies recommend them. Why? Valves normally fail from wear and tear right? Wouldn't this mean the master valve will fail first? If a master valve fails how would you know? The water now flows to each zone and the zone valves function as normal. If a zone valve fails how would you know? The master valve is now controlling the zone. Everything still looks normal. If a master and zone valve fail then you would end up changing both valves. More money for somebody..... OK...so what if we don't install the master valve. Then a zone valve fails...easy to tell it's failed....it's the one that keeps irrigating constantly. Whats your opinion?