When I turn on my ouside back faucet/spigot, the water in the house will not work. Toilets, sinks, etc. When I turn on the front ouside faucet/spigot, the water is fine all around the house. We have great pressure, and no troubles any other time, unless we use this back faucet. What on earth is going on? I am befuddled, and in need of help! Thank you.