Water Heater draining

: Water heater (approx 15 yr old gas) drained slowly about 3 gallons of water. I then shut off outlet valve to house for several hours and it stopped draining after I turned the outlet valve back on. What is going on?HELLO, AL!!Two possibilities as I see it: 1. You are trying to pukll a vacuum on the system when draining the tank (as the water escapes there is no way for more air or water to enter the system). Opening a hot water valve anywhere in the house will cure this.or 2. You havent drained the tank in a long time, and enuf sediment has built up to completely clog the drain. [If a gas HWH, think about the extra heat required to penetrate this gunk! You may have to completely remove the drain bibb to get drainage (watch out if the water is hot!). If it is plastic, just throw it away and get a new METAL one.Now, what about the *anode*?! If not replaced at the end of the warranty period, and every five years thereafter, you may be beating a (nearly) dead horse. Anode replacement is critical to continued life oa a HWH.GOOD LUCK!!!Darrel

: Water heater (approx 15 yr old gas) drained slowly about 3 gallons of water. I then shut off outlet valve to house for several hours and it stopped draining after I turned the outlet valve back on. What is going on?HELLO, AL!!Two possibilities as I see it: 1. You are trying to pull a vacuum on the system when draining the tank (as the water escapes there is no way for more air or water to enter the system). Opening a hot water valve anywhere in the house will cure this.or 2. You havent drained the tank in a long time, and enuf sediment has built up to completely clog the drain. [If a gas HWH, think about the extra heat required to penetrate this gunk! You may have to completely remove the drain bibb to get drainage (watch out if the water is hot!). If it is plastic, just throw it away and get a new METAL one.Now, what about the *anode*?! If not replaced at the end of the warranty period, and every five years thereafter, you may be beating a (nearly) dead horse. Anode replacement is critical to continued life oa a HWH.GOOD LUCK!!!Darrel